Patent Publication Number: US-2006018012-A1

Title: Apparatus and methods for focusing and collimating telescopes

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This application relates to focusing and collimation of telescopes such as for example Schmidt-Cassegrain telescopes and Maksutov-Cassegrain telescopes.  
      2. Description of the Related Art  
      Astronomy, and in particular, optical astronomy is increasingly popular, and advancements have been introduced in recent years to the instruments used for astronomical observation. High performance optical telescopes for the amateur and more advanced enthusiast may include, for example, diffraction limited optical systems offering high resolving power as well as CCD cameras for recording vivid images. Such telescopes may have accurate computer controlled drive systems for positioning the telescope using databases of deep-sky objects, stars, objects in our solar system and even earth satellites. With such sophisticated equipment to assist the astronomer, astronomy can be wonderfully enjoyable while the images obtained can be impressive and awestriking.  
      Proper focusing and collimation are important for quality imaging. Telescopes are designed to collect substantially collimated light from distant objects in the sky and to focus the light onto a focal plane. In a Cassegrain telescope, light is collected by a large primary mirror and reflected toward a secondary mirror, which reflects the beam of light to the focal plane. (The primary mirror may alternatively be referred to herein as the primary, while the secondary mirror may alternatively be referred to herein as the secondary as is customary in the art.) The curved primary and secondary mirrors focus the beam onto the focal plane where an ocular or camera may receive the light for viewing or recording an image. The optical system, comprising the primary longitudinally displaced along an optical axis a distance from the secondary mirror, has an effective focal length, which is determined in part by this longitudinal separation. The longitudinal distance separating the primary and secondary may be adjusted to alter the location where the images come to focus. Conventional telescopes are focused by translating the primary mirror such that a sharp image is formed at the desired image plane.  
      Proper orientation of the mirrors with respect to the optical axis and to each other are also important for quality imaging. Misalignment in the form of tilt of the primary or secondary may result in image distortion.  
      What is needed are methods and designs for effectively focusing and collimating telescopes.  
     SUMMARY OF THE INVENTION  
      Various non-limiting embodiments described herein include but are not limited to telescopes and apparatus and methods for focusing and collimating telescopes. One embodiment of the invention, for example, comprises a catadioptric telescope. This catadioptric telescope includes a tube assembly having a front cell and a rear cell. This tube assembly comprises a hollow telescope tube with proximal and distal ends. The rear cell is at the proximal end of the telescope and the front cell is at the distal end of the telescope tube. A primary mirror is disposed in the rear cell of the tube assembly. A corrector cell is distal to the front cell of the tube assembly. The corrector cell houses a corrector plate. A secondary mirror is centrally located with respect to and affixed to the corrector plate in the corrector cell. At least one electrically driven actuator is mounted to the front cell and the corrector cell so as to mechanically connect the corrector cell to the front cell. The actuator is movable in a controllable manner such that the corrector cell may be moved with respect to the front cell of the tube assembly and the corrector plate and secondary mirror can be moved with respect to the primary mirror. Control electronics are electrically connect to the electrically driven actuator. The control electronics have an output that provides signals to the electrically driven actuator to control movement of the actuator.  
      Another embodiment of the invention comprises a method of focusing a catadioptric telescope comprising a primary mirror, a secondary mirror, and a corrector, wherein the secondary mirror is affixed to the corrector. The method comprises monitoring feedback indicative of image focus for the catadioptric telescope and manipulating the corrector with one or more actuators mechanically connected to the corrector based on the feedback indicative of the image focus. The secondary mirror moves with the corrector so as to improve the focus of the telescope.  
      Another embodiment of the invention comprises a method of collimating a catadioptric telescope comprising a primary mirror, a secondary mirror, and a substantially optically transmissive optical element, wherein the secondary mirror is affixed to the substantially optically transmissive optical element. The method comprises (i) monitoring feedback indicative of the state of collimation of the catadioptric telescope and (ii) manipulating the substantially optically transmissive optical element with at least one actuator mechanically connected to the substantially optically transmissive optical element based on the feedback indicative of the state of collimation. The secondary mirror moves with the substantially optically transmissive optical element so as to improve collimation of the telescope.  
      Another embodiment of the invention comprises a catadioptric telescope comprising a primary mirror, a substantially optically transmissive optical element, and a secondary mirror. The primary mirror and the substantially optically transmissive optical element are disposed along an optical path through which light entering the telescope may propagate. The secondary mirror is affixed to the substantially optically transmissive optical element. The optical path continues onto the secondary mirror from the primary mirror. The catadioptric telescope further comprises a supporting structure for supporting the primary mirror and substantially optically transmissive optical element and one or more actuators are movable such that the substantially optically transmissive optical element and secondary mirror affixed thereto may be moved with respect to the primary mirror. The actuators comprises an electro-mechanical driver having electrical inputs and a rotatable threaded shaft connected to the electro-mechanical driver. The electro-mechanical driver rotates the threaded shaft with application of electrical power to the electrical inputs. A threaded coupler is threadedly connected to the rotatable threaded shaft such that the threaded fastener moves in a longitudinal direction along the rotatable threaded shaft when the shaft rotates. At least a portion of the substantially optically transmissive optical element can be translated when the rotatable threaded shaft is rotated by the electro-mechanical driver.  
      Another embodiment of the invention comprises a catadioptric telescope comprising a primary mirror, a secondary mirror, and a tube assembly. The tube assembly comprises sidewalls that form a hollow inner region and has an optical aperture through which light enters the hollow central region. The catadioptric telescope further comprises at least one electrically driven actuator disposed at the sidewalls of the tube assembly and connected to the secondary mirror such that the secondary mirror may be moved with respect to the primary mirror. Control electronics having an output provide signals to the electrically driven actuator to control movement of the actuator.  
      Another embodiment of the invention comprises a catadioptric telescope comprising a primary mirror, a secondary mirror, and a tube assembly. The tube assembly comprises sidewalls that form a hollow inner region and has an optical aperture through which light enters the hollow central region. This optical aperture is no more than about 12 inches across. The catadioptric telescope further comprises at least one actuator disposed with respect to the secondary mirror such that the actuator may move the secondary mirror with respect to the primary mirror.  
      Another embodiment of the invention comprises a method of focusing a catadioptric telescope comprising a primary mirror, a secondary mirror, and a corrector wherein the secondary mirror is affixed to the corrector. In this method, positioning data is retrieved from a record. The positioning data relates to the position of the corrector. The corrector is manipulated with at least one electrically driving actuator mechanically connected to the corrector based on the retrieved positioning data. The secondary mirror moves with the corrector to alter focus.  
      Another embodiment of the invention comprises a catadioptric telescope comprising a telescope tube, a primary mirror, and a corrector. The corrector and the primary mirror are disposed along an optical path through the telescope tube. At least one connector connects the corrector to the telescope tube. The corrector is separated from the telescope tube by substantially thermally insulating regions. A secondary mirror is affixed to the corrector. The optical path continues to the secondary mirror from the primary mirror. A source of heat is disposed with respect to the corrector to heat the corrector. The substantially thermally insulating regions reduce thermal conduction of the heat from the corrector to the telescope tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic cross-sectional view of a Schmidt-Cassegrain telescope comprising a primary spherical mirror, a secondary mirror, and a corrector plate rigidly affixed to the secondary mirror;  
       FIG. 2  is a schematic cross-sectional view of a Maksutov-Cassegrain telescope comprising a primary mirror, a secondary mirror, and a corrector plate wherein the secondary mirror comprises a reflecting surface formed on the corrector plate;  
       FIG. 3  is a perspective view of a catadioptric telescope comprising actuators for moving the corrector plate and secondary mirror for use in focusing and collimating the telescope;  
       FIG. 4  is a close-up perspective view of one of the actuators shown in  FIG. 3 .  
       FIG. 5  is a close-up top view of one of the actuators shown in  FIG. 3 .  
       FIG. 6  is a cross-sectional view along the line  6 -- 6  of the actuator shown in  FIG. 5  depicting the drive box assembly used to move the corrector plate and secondary mirror.  
       FIG. 7  is a front view of the corrector plate and actuators.  
       FIG. 8  is a cross-sectional view of the corrector plate and actuators taken along the line  8 -- 8  in  FIG. 7 .  
       FIG. 9  is a block diagram schematically illustrating one embodiment of a control system comprising control electronics for controlling motion of the actuators.  
       FIG. 10  is a schematic drawing of a tube assembly including conduits for the motor, drive shaft, and drive box assembly for the actuators that manipulate the corrector plate and secondary mirror.  
       FIG. 11  is a schematic drawing of a telescope including a tripod and a fork assembly supporting a tube assembly and controller.  
       FIG. 12  is a schematic diagram of an image of a point source such as a star with a telescope that is sufficiently focused and collimated.  
       FIG. 13  is a schematic diagram of an image of a point source obtained with a telescope system that is out of focus.  
       FIG. 14  is a schematic diagram of a distorted image of a point source obtained with a telescope wherein the primary and secondary mirrors are misaligned. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  depicts a telescope  10  comprising a primary mirror  12 , a secondary mirror  14 , and focal plane  16 . The telescope  10  further comprises a refracting corrector plate  18 . The primary  12 , secondary  14 , and corrector  18  are aligned about an optical axis  20  centrally located through the telescope  10 . This optical axis  20  is designated the z-axis in  FIG. 1  and has orthogonal x- and y-axes. The primary mirror  12  may have, for example, a metallized parabolic reflecting surface  21 , although the reflecting surface may have other shapes such as spherical or aspherical and should not be limited. The primary mirror  12  may comprise glass or Pyrex that is polished or shaped to form the curved reflecting surface  21 . The secondary mirror  14  also has a curved reflecting surface  22 . Like the primary  12 , the secondary mirror  14  may also comprise glass and may be polished and metallized to form the curved reflecting surface  22 . Other materials can be used for the primary and secondary mirrors  14 ,  18 .  
      The refractive corrector plate  18  is preferably a substantially transmissive optical element comprising for example glass or other materials. The corrector plate  18  preferably has at least one, and possibly two shaped surfaces, which may be aspheric. The corrector plate  18 , however, preferably has negligible optical power.  
      This telescope  10 , having both reflective and refractive optical elements, is a catadioptric telescope. This particular configuration, which includes the combination of the primary and secondary mirrors  12 ,  14  and corrector plate  18 , may be referred to as a Schmidt-Cassegrain. The curvature of the corrector plate  18  is different and distinct from that of the secondary mirror  14 . Preferably, however, the secondary mirror  14  is rigidly affixed to the corrector plate  18  such that the two optical elements are connected together.  FIG. 1  shows a baffle  24  between the corrector  18  and the secondary  14 , however, preferably the corrector is attached to the secondary mirror through the baffle or other structure that secures the corrector and the secondary together.  
      In various preferred embodiments of the present invention, the secondary mirror  14  can be moved to focus and collimate the telescope  10 . The secondary  14  can be translated longitudinally along the longitudinal (z-axis), toward or away from the primary  12  to focus. The secondary  14  preferably can also be tilted in different directions to collimate. For example, the secondary  14  may be tilted about the orthogonal x- or y-axes or other axes orthogonal to optical axis  20 . The secondary  14  may be tilted about a center located on the optical axis (z-axis) or about off-axis centers as well. Other orientations for the secondary mirror  14  may be possible as well.  
      In preferred configurations where the secondary mirror  14  is affixed to the corrector plate  18 , the corrector plate  18  may be translated or tilted to effectuate the desired longitudinal displacement or tilt of the secondary mirror  14 . One or more actuators, for example, may be affixed to the corrector plate  18  to execute such movements. In various preferred embodiments, these actuators are at the perimeter of the corrector plate  18  and manipulate the corrector plate from its perimeter.  
      As shown, collimated rays from, for example, a celestial object, are received by the telescope  10 . Preferably, the collimated rays pass through the corrector plate  18  without being substantially deviated such that movement of the corrector plate would interfere with quality imaging. In other embodiments discussed more fully below, the secondary may be affixed to a substantially optically transmissive plate such as an optical flat or window or is supported by a support structure such as vanes. Accordingly, the angle of the light may therefore not be altered by refraction. The collimated light propagates to the primary mirror  12  where the curved concave reflecting surface  21  converts the collimated beam into a converging beam directed toward the secondary mirror  14 . The converging beam reflects off the convex curved reflecting surface  22  of the secondary mirror  14 . The beam continues to converge toward the focal plane  16  where the beam is focused.  
      An image of the object is formed at this focal plane  16 . Accordingly, an optoelectronic imaging device such as a CMOS or CCD camera can be disposed at, near, or with respect to the focal plane  16  to record an image of the object. Alternatively, an ocular can be positioned relative to the focal plane  16  to permit viewing of the image with the eye. In other configurations, optics or optical instruments, such as for example a spectrometer, can be suitably located with respect to the focal plane  16  to receive the light from the distant object.  
      The location where the image comes to focus is determined by the focal length of the telescope  10  and the location of the primary and secondary mirrors  12 ,  14 . The focal length of the telescope  10  depends on the power of the primary and secondary mirrors  12 ,  14  and the longitudinal distance separating the primary from the secondary, which is shown in  FIG. 1  as d 1 . Longitudinally displacing the secondary mirror  14  in relation to the primary mirror  12 , which increases or decreases d 1 , therefore, shifts the focal plane of the telescope  10 . Accordingly, by adjusting the separation of the primary and secondary mirror  12 ,  14 , the focus of the image may be altered. Additionally, presuming that the focal length were held fixed, translation of the mirrors causes the focal plane, (shown in  FIG. 1  to be distance d 2  from the secondary) to be displaced longitudinally as well. Accordingly, the secondary mirror  14  can be translated in a direction parallel to the longitudinal axis (z-axis) thereby shifting the location of the focal plane  16  with respect to, for example, a camera, ocular, or other optics. For these reasons, the telescope  10  can be focused by translating the secondary mirror  14  along the longitudinal axis.  
      The telescope  10  may also be collimated by moving the secondary  14  to improve the image quality. If the primary  12  and/or the secondary  14  are misaligned, e.g., tilted with respect to the optical axis  20 , each other, or the focal plane  16 , the image may be distorted. The telescope  10  is said to need collimation or alignment. The secondary mirror  14  may be tilted to correct this distortion. Accordingly, adjustment of the orientation of the secondary mirror  14  can therefore be adjusted to collimate the beam and enhance the clarity of the image.  
       FIG. 1  shows arrows  26 ,  28  schematically depicting possible movement of the corrector plate  18  and the secondary mirror  14 , for example, in the longitudinal direction or tilting of the corrector plate and secondary mirror. In various preferred embodiments, the secondary mirror  14  is attached to the corrector  18  such that translation or canting of the corrector  18  displaces or reorients the secondary mirror in a similar manner. Accordingly, actuators configured to move the corrector plate  18  may, consequently, alter the position of the secondary  14  and thus focus the telescope  10  or change attitude of the secondary  14  and collimate the telescope.  
      Another telescope design, known as a Maksutov-Cassegrain telescope, is shown in  FIG. 2 . In this catadioptric telescope  10 , the secondary mirror  14  forms part of the corrector  18 . In particular, the corrector  18  comprises a curved refractive optical element having forward and rearward surfaces  30 ,  32 . The forward surface  30  is directed toward the object and the rearward surface  32  faces the primary  12 . The corrector plate  18  depicted in  FIG. 2  is substantially optically transmissive with the exception of a central region  34  thereof. The forward and rearward surface  30 ,  32  of the corrector  18  are concave transmissive surfaces to light propagating from a celestial object through the corrector  18  and to the primary mirror  12 . In various preferred embodiments, the central portion  34  of the rearward surface  32  is metallized to form a substantially reflective surface corresponding to the secondary mirror  14 . Other reflective coatings may also be employed as well. As a result of the shape of the corrector  18 , the secondary mirror surface is convex. Also, since the secondary mirror  14  is formed on a surface  32  of the corrector lens  18 , adjusting the position and orientation of the corrector such as for example schematically represented by arrows  26 ,  28  causes similar movement of the secondary reflector  14 . Accordingly, the corrector  18  can be displaced longitudinally along the optical axis  20  to impart the desired translational motion to focus the telescope  10 . Additionally, the corrector  18  can be tilted to introduce the desired amount of tilt in the secondary  14  to collimate the telescope  10 . Focus and collimation of the telescope  10  can thus be accomplished by establishing the appropriate position and orientation, respectively, of the secondary mirror  14 .  
      The specific optical designs and configurations of the telescope  10  should not be limited to those specifically described with reference to  FIGS. 1 and 2 . For example, the primary  12 , secondary  14 , and corrector  18  may have spherical or aspheric surfaces. These optical elements  12 ,  14 ,  18  may comprise glass, Pyrex, or other transmissive or non-transmissive materials. The reflective surfaces may be formed by metallization. Reflecting coatings of other types may be used as well. In different embodiments of the invention, reflective surfaces or structures may be otherwise created. The telescope  10  may include additional components such as baffles, stops, reflectors, lenses, polarizers, filters, holographic or diffractive optical elements and other optical elements. The telescope  10  may further comprise an ocular, a photographic or optoelectronic camera, optical instruments, as well as other subsystems, devices, and accessories.  
      In some preferred embodiments, the secondary  14  is connected to an optical element such as for example a substantially optically transmissive plate (e.g. glass plate or optical flat) instead of a corrector  18 . Such an optical element may or may not have one or more curved surfaces and may or may not have optical power. The optical element, e.g., optical plate, lens, etc., may be moved in a manner discussed above to manipulate the position and orientation of the corrector  18 . This optical element may be moved by one or more actuators  36  peripheral to the optical element. As with the corrector  18  plate, light would pass through the substantially optical element to the primary and secondary mirrors.  
      In other embodiments, the corrector  18  is replaced with a support structure such as one or more vanes secured to the secondary. The support structure may be moved by one or more actuators  36  to alter the position and/or orientation of the secondary mirror  14 . These actuators  36  are preferably disposed in peripheral areas of the support structure so as to reduce obstruction of light that would otherwise propagate through the telescope  10  to the primary  12 . Similarly, in the case where one or more vanes is employed to support the secondary mirror  14 , the vanes are preferably substantially thin with respect to the aperture of the telescope  10  such that the vanes do not prevent a substantial portion that would otherwise reach the primary mirror  12 . Alternatively, the vanes or supports may be substantially optically transmissive.  
      An embodiment of the telescope  10  comprising a focusing/collimation assembly  35 , which comprises a plurality of actuators  36  for manipulating the corrector plate  18 , is illustrated in  FIG. 3 . The telescope  10  shown in  FIG. 3  includes three such actuators  36 . Close-up perspective and top views of a portion of the actuators  36  is depicted in  FIGS. 4 and 5 . A cross-sectional view through one of the actuators  36  is presented in  FIG. 6 . A front view of the telescope  10  and a cross-section through the focussing/collimation assembly  35  and secondary mirror  14  and corrector plate  18  is shown in  FIGS. 7 and 8 .  
      As shown in  FIG. 3 , the telescope  10  comprises a tube  38  that forms part of a tube assembly  40  for housing the primary mirror  12 , secondary mirror  14 , and corrector  18 . The tube  38  has a front (or distal end) and a rear (or proximal end) designated the front cell  42  and the rear cell  44 . The distal end of the tube  38  may be directed toward a celestial object to be viewed.  
      A corrector cell  46  is forward of the front cell  42  and houses the corrector plate  18 . A space may separate the corrector cell  46  from the front cell  42  of the tube  38  (not shown). This space may be covered by a flexible skirt (not shown) comprising for example rubber, cloth, plastic, synthetic fabric, or other material for blocking light and dust, etc., from entry into the tube assembly  40 . The secondary mirror  14  (see  FIG. 8 ) is located at the center of the corrector plate  18 . The primary mirror  12  is disposed at the rear cell  44 . The rearward portion of the tube assembly  40  is essentially closed-off by a cell back  50  affixed to the rear cell  44 . Photographic and optoelectronic cameras as well as other components and accessories can be connected to this cell back  50  in various embodiments. Preferably, the primary mirror  12  is firmly secured in the rear cell  44  using for example cement, glue, epoxy, silicone couching or other material to adhered the primary mirror to the cell back  50 . The primary  12  may otherwise be connected, for example, to the tube assembly  40  or other rigid framework that preferably serves as a platform for the telescope optics. Fasteners or other devices for fixing the primary mirror  12  in place may be used as well. Rigidly securing the primary mirror  12  in place reduces misalignment and shifts due, for example, to vibration that may be introduced during focusing or collimation. Preferably, the primary mirror  12  will not become inadvertently tipped, tilted, or displaced, and thereby misaligned. In other embodiments, the primary mirror  12  may have a position and orientation that is adjustable, however, the primary is preferably rigidly affixed in place in various preferred embodiments.  
      As shown in  FIG. 7 , three actuators  36  may be employed and these actuators  36  may be disposed about a circular perimeter of the telescope  10  centered about the optical axis  20  through the telescope. In various preferred embodiments, these actuators  36  are separated azimuthally by about 120° about the optical axis  20  although the positions and respective azimuthal angles separating the actuators may vary and should not be limited.  
      In the embodiments depicted in  FIGS. 3-8 , each of the actuators  36  includes an electrical motor  52  in the proximity of the rear cell  44  of the telescope tube  38 . The motor  52  is shown mounted to a mounting bracket  53 . Preferably, this mounting bracket  53  is mounted to the tube assembly  40  or the motor is otherwise secured in place. A rotatable shaft extends from the motor  52  and rotates when the motor is activated.  
      In these embodiments, the actuators  36  further comprises a drive shaft  58  and a drive box assembly  60 . The drive shaft  58  has a proximal end connected to the rotating motor shaft via drive gears  51  such that rotation of the motor shaft induces corresponding rotation of the drive shaft. In these embodiments, the actuator  36  further comprises an encoder  55  to track rotation of the motor  52 . Preferably, this encoder  55  outputs a precise measure of the angular position of the rotating motor shaft and the drive shaft  58 . A position sensor board  57  preferably includes electronics that outputs electrical signals from the encoder  55  based on the position of the rotatable motor shaft and drive shaft  58 . These electrical signals may be communicated to control electronics as discussed more fully below.  
      As shown in  FIG. 5 , the drive shaft  58  has a distal end connected to a drive shaft bushing  61  on the drive box assembly  60 .  FIG. 5  depicts this drive shaft  58  in phantom. The drive box assembly  60  comprises a frame  62  that supports a threaded drive screw  63  which is rotatable. The drive shaft bushing  61  is connected to the threaded drive screw  63  through drive gears such that rotation of the drive shaft  58  and consequent rotation of the drive shaft bushing  61  causes rotation of the drive screw  63 . The drive box frame  62  supports a guide pin  66  that extends a substantially parallel to the drive screw  63 . The guide pin  66  passes through a coupler  68 , which rides on the guide pin. An opening through coupler  68 , through which the guide pin  66  passes, permits movement of the coupler in a longitudinal direction along the guide pin. The coupler  68  further comprises a threaded opening through which the threaded drive screw  63  passes. Rotation of the threaded drive screw  63  causes the coupler  68  to be longitudinally translated along the guide pin  66  in a direction parallel to the guide pin and the threaded drive screw as indicated by arrows  70 . This direction is parallel to the z-axis shown in  FIGS. 4-6 . The drive box assembly  60  may further include a position sensing device comprising a position indicator  69  and a limit sensor board  71  having a pair of emitters  73   a  and detectors  73   b  for position sensing. This position sensing device together with the encoder  55  may enable precise tracking of the movement introduced by the actuator  36 .  
      The coupler  68  is pivotably connect to a swivel yoke  72  by a pair of nut pins  74  that fit into opening in the coupler. These nut pins  74  screw into the swivel yoke  72 , extending through the swivel yoke to the coupler  68 . The pair of nut pins  74  establish pivot points that permit the swivel yoke  72  to rotate with respect to the coupler  68 . In particular, the swivel yoke  72  may rotate about an axis through the nut pins  74  parallel to the x-axis shown in  FIGS. 4-6 . This angular motion is schematically illustrated in  FIG. 6  by arrows  75 .  
      One end of a swivel pin  76  fits in a cylindrical opening in the swivel yoke  72 . Another end of the swivel pin  76  fits into another cylindrical opening in a swivel pin block  82  (see  FIG. 8 ). This swivel pin  76  preferably permits movement of the swivel yoke  72  about an axis through the swivel pin parallel to the y-axis shown in  FIGS. 4-6 . This angular motion is schematically illustrated in  FIG. 6  by arrows  77 . Accordingly, the swivel pin  76  and the swivel pin block  82  can rotate with respect to the swivel yoke  72 . The swivel pin  76  also preferably can move in a longitudinal direction parallel to the y-axis in  FIGS. 4-6  as well. This axial motion is indicated by arrows  78  in  FIG. 6 . The swivel pin  76  can therefore preferably move in inward and outward directions with respect the opening in the swivel pin block  82  in which the swivel pin fits. The swivel yolk  72  and the swivel pin block  82  may thus have increased or reduced separation therebetween. The swivel pin block  82  is molded to a corrector cell plate  80  shown in  FIGS. 3 and 8  and is thereby firmly secured to the corrector cell  46  and the corrector optic  18 . The actuator  36  is thus mechanically linked to the corrector cell  46 , the corrector  18 , and the secondary mirror  14 .  
      The actuator  36  is also mechanically connected to the front cell  42  of the telescope  10 . In this embodiment, the frame  62  of the drive box assembly  60  is mounted to a drive assembly mounting plate  84  (shown in  FIG. 3 ) that is firmly secured to the telescope tube  38 . In the embodiment shown, the drive assembly mounting plate  84  comprises a ring-shaped or annular plate having an inner diameter substantially matched to the telescope tube  38 . The drive assembly mounting plate  84  may support each of the drive box assembly units  60  for the three actuators  36  and thus form a physical connection to all three actuators.  
      Accordingly, the actuator  36  can be activated to re-position the secondary mirror  14 . The motor shaft may be rotated in a controlled manner based on signals applied to the motor  52 . Rotation of the motor shaft causes similar rotation of the drive shaft  58  and the threaded drive screw  63 . The coupler  68  through which the drive screw  63  is threadedly connected, is translated with respect to the drive screw and the drive box assembly  60  as a result of the rotating drive screw. Displacement of the coupler  68  causes the swivel yoke  72 , the swivel pin  76 , and the swivel pin block  82  to be shifted and tilted with respect to the drive screw  63  and drive box assembly frame  62 . Likewise the portion of the corrector cell  46  attached to the swivel pin block  82  via the corrector cell plate  80  is shifted with respect the front cell  42 . The front cell  42  is also connected to the drive box assembly  60  through the drive assembly mounting plate  84 . Shifting of this portion of the corrector cell  46  and similarly the corrector plate  18  may cause the corrector plate and the secondary mirror  14  to be tilted with respect to the telescope tube  38  and the primary mirror  12 .  
      Activation of any single one or any combination of the actuators  36  together may be used to shift and/or tilt or tip the secondary mirror  14  as desired. For example, translation of each of the actuators  36  by equal amounts may in certain circumstances cause longitudinal displacement of the corrector cell  46  and secondary mirror  14  parallel to the optical axis  20 . Shifting the corrector cell plate  80  by different amounts at the different actuator locations may cause the secondary mirror  14  to be tilted or tipped and may or may not include longitudinal displacement of the secondary toward or away from the primary mirror  12 .  
      Preferably the encoder  55  and the position sensing device in the drive box assembly units  60  permit the movement and position to be precisely monitored. Signals from the encoder  55  and position sensing device in the drive box  60  can be used to determine location and to thereby adjust the corrector  18  and secondary  14  in a controlled manner. Other types of position sensing and monitoring devices may be employed in other embodiments. In some embodiments, such position/movement sensors may be excluded.  
      Advantageously, the actuators  36  are configured to prevent binding and possible seizure. As the actuators  36  are used to tip and tilt the corrector cell  46 , the orientation of the corrector cell may vary causing varyingly directed forces to be applied to the actuators. Preferably, the actuator  36  is designed to accommodate the movement of the corrector cell  46  and to avoid binding that may result from tension on the components of the actuator. For example, the pair of nut pins  74  permit swivel of the swivel yoke  72  with respect to the drive screw  63  and drive box assembly  60 . This motion is represented by the arrow  75  in  FIG. 6 . Upon rotation of the drive screw  63  and consequent translation of the coupler  68 , the angle of the swivel yoke  72  with respect to the swivel nut pins  74  and drive screw is thus free to change. In addition, the swivel yoke  72  may rotate about the swivel pin  76  and with respect to the swivel pin block  82 . This angular motion is schematically represented by the arrow  77  in  FIG. 6 . Accordingly, if an adjacent actuator  36  is activated to tilt the corrector  18  and secondary mirror  14 , the corrector cell  46  may tilt causing the swivel pin block  82  to rotate with respect to the swivel yoke  72 . Binding and seizure can therefore be avoided when the corrector cell  46  is so tilted. The swivel yoke  72  may also be moved closer or farther from the swivel pin block  82  depending on the attitude of the corrector cell  46  with respect to the front cell  42  and the actuators  36 . Advantageously, the swivel pin  76  fits into openings in the swivel yoke  72  and the swivel pin block  82  and is able to move longitudinally along a direction parallel to the pin&#39;s length. As a result, the swivel yoke  72  is able to move with respect to the swivel pin block  82 . The longitudinal movement of the swivel yoke  72  with respect to the swivel pin block  82  is schematically represented by the arrow  78  in  FIG. 6 .  
      The actuators  36  depicted in  FIGS. 3-6  represent various non-limiting embodiments of devices for manipulating the secondary mirror  14  and should not be construed as limiting. Other structures and designs may be used in other embodiments of the invention.  
      Although three actuators are shown in  FIG. 3 , more or less actuators may be employed. For example, one or more actuators may be used to focus the telescope  10 . Two or more actuators may be used to collimate the telescope  10 . Also, although a corrector  18  is shown, the secondary  14  may otherwise be supported by, e.g., an optical element such as a lens, an optical flat, or an optical plate that is not a corrector. One or more vanes or support beams or by other types of support structures may also be employed. The secondary  14  likewise may be manipulated by movements of these support structures. Preferably, the secondary  14  is manipulated by movement of actuators  36  disposed about the optical path where light propagates to the primary mirror  12  so as to reduce obstructions to light throughput to the primary mirror. For example, the telescope tube  38  may comprise sidewalls surrounding an inner region through which light passes to the primary  12 . The actuators  36  may be disposed at these sidewalls. In various preferred embodiments, the actuators  36  are disposed outside these sidewalls such that the secondary mirror  14  is moved from beyond the inner region of the telescope  10  where light propagates to the primary  12  thereby reducing obstructions. Accordingly, the actuators  36  may be connected to the perimeter of the corrector  18  or other optical plate or at locations on the vanes or other support structures remote from the secondary  14 . By placing the actuators  36  a distance from the secondary  14  and outside or at least less in the optical path of the light to the primary  12 , more light may be collected by the primary.  
      A controller  94  such as shown in a block diagram format in  FIG. 9  may assist the user in focusing and collimating the telescope  10 . In one preferred embodiment, the controller  94  is electrically connected to control electronics  96  as schematically illustrated in  FIG. 9 . The controller  94 , the control electronics  96 , and the actuators  36  may together form a control system  98  as shown by the block diagram. The controller  94  may act as the user interface through which a user issues instructions for manipulating and/or adjusting the telescope  10 . The controller  94  may, for example, include a display for presenting information to the user and a keypad through which the user inputs instructions or data. For instance, to focus the telescope  10  the user can translate the corrector  18  and secondary mirror  14  toward or away from the primary mirror  12  by depressing these keys as will be discussed more fully below. The controller  94  may also include keys for specifying tilt or tip of the secondary  14  and corrector  18  to enable collimation. Although in some embodiments these keys may comprise buttons disposed on the controller  94 , other touch sensitive surfaces may be employed as well. Various other configurations are also possible.  
      The control electronics  96  are preferably configured to receive signals output by the controller  94  and to drive the actuators  36  according to commands specified by the user. The control electronics  96  may comprise, for example, a computer or microprocessor or other electronics for processing signals from the controller  94 . The control electronics  96  are preferably electrically connected to the actuators  36  and in particular to the motors  52  in the actuators. In one preferred embodiment, the control electronics  96  comprises digital electronics for sending control signals to the motors  52  in the actuators  36 , which may comprise, e.g., D.C. servos, stepper motors, etc. In various preferred embodiments, the control electronics  96  comprise logic circuitry for converting instructions specified by the user with the controller  94  into the appropriate control signals for controlling the motors  52  and actuators  36  so as to fulfill the user&#39;s commands. For example, translating the secondary mirror  14 , toward or away from the primary mirror  12  may involve movement of all three actuators  36  in the embodiment shown in  FIG. 7 . Tilting or tipping the secondary mirror  14  may comprise suitable movement of one of the actuators  36  or a combination of the actuators. Preferably, the control electronics  96  comprise the logic to determine the appropriate actuator  36  movement to effectuate the commands specified by the user. In a three point system such as shown in  FIG. 7 , for instance, the controller  96  preferably can cause the actuators to tip, tilt or translate the secondary  14  appropriately. For example, when focussing, the control electronics  96  preferably is capable of moving the actuators  36  in a suitable manner to introduce longitudinal displacement of the secondary mirror  14  while maintaining the secondary mirror properly centered and properly oriented. Additionally, when the secondary  14  is tipped and/or tilted during collimation, the secondary mirror also preferably remains focused. As discussed more fully below, the telescope assembly  40  may be reoriented (e.g., rotated and canted) to track the celestial object used to collimate and focus the telescope.  
      The control electronics  96  may also include logic to implement additional processes and features. For example, the process of focusing or collimating the telescope  10  may be automated. An image obtained by an opto-electronic camera such as a CCD or CMOS digital camera can be processed to determine whether the telescope  10  is focused or collimated and to determine suitable adjustments to the orientation and/or the position of the secondary mirror  14  to implement correction. Control signals based on these determinations may be sent to the actuators  36  to adjust the secondary mirror  14  accordingly. The control electronics  96  are also preferably configured so as not to permit the telescope  10  to bind, seize, or extend beyond the telescope&#39;s operating range. Other features may also be included. As described above, the actuators  36  may be outfitted with position sensors devices as well as encoders  55 . These sensors may assist in limiting the movement to within a safe operating range.  
      The encoder  55  and position sensor devices in the actuators may additionally be employed to move the corrector  18  to a suitable or desired location. For example, pre-programmed focus positions may be stored for multiple users. Upon identifying the user, the telescope  10  may use, for example, the encoder  55  to set the particular longitudinal position of the secondary  14  for that user. The user may identify themselves by entering such information into the controller  94 . In other embodiments, the telescope  10  may determine the user&#39;s identity by recognition of a user-identifying characteristic such as retinal pattern etc. Similarly, a database of objects with corresponding focuses may be stored and the actuators  36  may automatically adjust the focus of the telescope  10  depending on which object is being viewed. The user may indicate the object to be viewed. In certain embodiments, the telescope  10  will be equipped with ability to locate that object and may also include automated focusing as described herein. The encoder  55  or other positioning sensing and controlling systems can be employed to control the actuator  36  such that the secondary  14  is moved as desired. Alternatively, the user may specify a distance such as infinity or 30 feet and the controller  94  may process this request and determine the appropriate location of the secondary  14  to provide proper focus for such a distance.  
      In certain embodiments, the telescope  10  can ascertain relevant optical specifications of different components or accessories such as different oculars or photographic and optoelectronic cameras. For example, different devices that may be incorporated into the telescope system may have different focal lengths and thus alter the focusing characteristics of the telescope  10 . This information can be employed by the controller  94  to suitably locate the secondary mirror  14  in the appropriate positions to provide an “in focus” image. Such information can be stored on the accessory, e.g., electronically, in certain embodiments.  
      The structure of the logic for various embodiments of the present invention as well as the logic for other designs may be embodied in computer program software. Moreover, those skilled in the art will appreciate that various structures of logic elements, such as computer program code elements or electronic logic circuits are illustrated herein. Manifestly, a variety of embodiments include a machine component that renders the logic elements in a form that instructs the actuators  36  or other apparatus to perform, e.g., a sequence of actions. The logic may be embodied by a computer program that is executed by the processor or electronics as a series of computer- or control element-executable instructions. These instructions or data usable to generate these instructions may reside, for example, in RAM, on a hard drive or optical drive, or on a disc. Alternatively, the instructions may be stored on magnetic tape, electronic read-only memory, or other appropriate data storage device or computer accessible medium that may or may not be dynamically changed or updated. Accordingly, these methods and processes including, but not limited to, those specifically recited herein may be included, for example, on magnetic discs, optical discs such as compact discs, optical disc drives or other storage devices or medium known in the art as well as those yet to be devised. The storage mediums may contain the processing steps which are implemented using hardware, for example, to control motion of the actuators  36 , to focus or collimate the telescope  10 , etc. These instructions may be in a format on the storage medium that is subsequently altered. For example, these instructions may be in a format that is data compressed.  
      The controller  94  and control electronics  96  depicted in  FIG. 9  represent various non-limiting embodiments of the invention and the control of the actuators  36  can be implemented in other ways as well. For example, a user interface other than the controller  94  may be employed. The user interface may comprise, for example, computer, laptop, palm top, personal digital assistant, cellphone, or the like. Information may be displayed on a screen, monitor, or other display, and/or conveyed to the user via, e.g., audio or tactilely, as well as visually. A keyboard or keypad, or one or more buttons, switches, and sensors can be used to input information such as commands, data, specification, settings, etc. A mouse, joystick, or other interfaces can be used as well. User interfaces both well known in the art, as well as those yet to be devised may be employed to input and output information and commands.  
      In addition, some or all of the control electronics may be included in the controller  94  or user interface. For example, in the case where the user interface comprises a computer, laptop, palm top, personal digital assistant, cellphone, or the like, both the interface as well as some or all of the control and processing electronics may be included in the computer, laptop, palm top, personal digital assistant, cellphone, etc. Additionally, some or all the processing can be performed all on the same device, on one or more other devices that communicates with the device, or various other combinations. The processor may also be incorporated in a network and portions of the process may be performed by separate devices in the network. Processing electronics can be included elsewhere on or external to the telescope  10  and may be included for example in the actuators  36 , as well as in or on the tube assembly  40  or elsewhere. The control electronics  96  may be in the form of processors, chips, circuitry, or other components or devices and may comprise non-electronic components as well. Other types of processing, electronic, optical, or other, can be employed using technology well known in the art as well as technology yet to be developed.  
      In addition, although motors  52  are shown as being used in the actuator  36 , other transducers for repositioning or maneuvering the secondary mirror  14  are possible. Other types of motors  52  including, for example, stepper motors, as well as non-motor driven devices and systems such as, e.g., piezo-electric or electromotive devices, hydraulic or pressure driven systems, etc., may be utilized as well. The particular implementation should not be limited to those described herein as other types of devices and systems for manipulating the secondary mirror  14  may be employed and are within the scope of the present invention.  
      In various embodiments the actuators  36  may extend along the tube  38  as shown in  FIG. 10 . Electrical and/or mechanical apparatus may be covered by shrouds or conduits  108  on the telescope tube  38 . For example, the motor  52 , drive shaft  58 , and drive box assembly  60  may be enclosed in a shroud. In various embodiments, the tube assembly  40  may be contoured to accommodate such conduits  108 . As described above, the telescope tube  38  may comprise, for example, carbon fiber, which preferably reduces thermal drift effects. The conduits  108  may comprise, for example, carbon fiber, vacuum formed plastic or sheet metal. Other materials may be used as well. In other embodiments, conductive paths may be incorporated in the telescope tube  38 . Signals other than electrical signals transmitted through conductive lines may be employed to control and/or communicate with the actuators  36 . Optical, RF, or other types of signals may be propagated, for example, along waveguides such as optical fibers or may be unguided such as via wireless communication.  
      The controller  94  and control electronics  96  may be disposed on a tripod  110  below a rotating fork  112  holding the tube assembly  40  as depicted in  FIG. 11 . The actuators  36 , motors  52 , drive shafts  58 , etc., are hidden from view in this embodiments. The controller  94  and/or control electronics  96  may be disposed elsewhere as well. In various embodiments, for example, control of the actuators  36  may be implemented via optical or RF signals or using other media to communicate with and/or deliver power to the actuators. As described above, the actuators  36  may be controlled by a computer such as a personal computer or a portable device such as a palm-held device or other device, network of devices, or system. Similarly, the control components and/or user interface can be located elsewhere and/or included in a variety of locations.  
      In addition, the actuator design need not be limited to the configurations described herein. Many variations are possible. For example, in different embodiments different parts that form the actuator  36  may be combined together. For instance, the swivel pin  76  and the swivel yoke  72  may be integrated into a single component or alternatively the swivel pin may be integrated together with the swivel pin block  82  to form a single structure. Similarly, the swivel pin block  82  separated from the corrector cell plate  80  or may be combined together. The drive box assembly frame  62  may possibly be integrated together with the drive assembly mounting plate  84  in some embodiments. In other preferred embodiments, however, these are separate components fastened together with suitable connectors or fasteners such as bolts and screws. Additionally, these components may be broken up into more or less component parts. Additional parts and features may also be added or components or design aspects may be removed. The design of the individual parts may be different or may be supplemented with additional components in other embodiments. Similarly, the connection between the components may be varied. For example, the connection between the actuator  36  and the secondary  18  may be different. For instance, the actuator  36  may be physically connected to the primary  12  through the drive assembly mounting plate  84  and the tube assembly  40  (including the telescope tube  38  and the rear cell  44 ) as well as other mounting components. In certain embodiments, the actuator  36  may be mechanically connected to the secondary  14  through the corrector plate  18  and any device used to connect these two optical elements as well as through the corrector cell  46  and the corrector cell plate  80 . Alternatively, the actuators may be connected to the secondary  14  through support structures other than the corrector such as optical flats, vanes beams, etc., as discussed above. Additional components may be included to form mechanical connection between the actuator  36  and the primary  12  and between the actuator and the secondary  14 . Alternatively, the physical connections may be formed otherwise, with less or more or different intervening components.  
      Other arrangements and designs may be employed including those based on conventional approaches to translation and positioning as well as translation and positioning concepts yet to be devised. Preferably, however, the actuators  36  are configured so as to prevent or reduce the likelihood of binding or seizure. Accordingly, three or more degrees of freedom may be provided. In other embodiments, however, more or less degrees of motion may be available with different designs. The actuators  36  may comprise metal components such as aluminum or stainless steel and may also include substantially temperature invariant materials such as Invar, which is substantially resistant to temperature induced changes. These components may be machined, molded, or otherwise manufactured. Also, although three actuators are shown, the number of actuators need not be limited to three. For example, one or two, or four or more actuators may be employed in different designs although three may be preferred. The location of the actuators  36  may also vary. Damping, shock absorption, vibration isolation, noise reduction or other features may also be included in various embodiments.  
      As described above, the user may actively focus and collimate the telescope  10  or a system may be included to automate the processes for focusing and collimation. In various embodiments, to focus, the telescope  10  is directed at the appropriate target object and is imaged. The image may be evaluated by measuring, e.g., the resolution, blur, or other figure of merit to determine whether the image is in focus. The actuators  36  may adjust the position of the corrector  18  and secondary  14  to improve the focus. Measurements of the image quality, blur, resolution, etc., can assist in such repositioning of the secondary  14 , and corrector  18  until a suitably focused image is obtained.  
      In the case where the telescope  10  is substantially focused and well collimated, an airy disc pattern preferably having substantially all optical energy in a central peak as schematically represented in  FIG. 12 , may be formed at the focal plane  16 . In some cases, this airy disc may comprise a plurality of concentric circular and/or annular bright portions. A substantial portion of the light, however, is preferably distributed in a peak at the center of the circularly symmetric pattern. The intensity may oscillate with distance away from the center resulting in annular peaks or rings. However, superimposed on this oscillation is a general decrease in intensity with distance from the center, the rings farther from the center being less bright than those closer to the center. In some preferred embodiment, these rings are absent as described above. A telescope  10  yielding such a pattern may not require focusing or collimation or adjustment of the secondary mirror  14  as the telescope may already be sufficiently focused and collimated. A user therefore observing a pattern during the focusing or collimation process that is indicative of proper focusing and collimation, such as for example an airy disc pattern, may conclude that the telescope  10  is properly focussed and collimated. Similarly, if an automated system is employed, an airy disc pattern at the focal plane may be imaged by an optoelectronic detector or other image detection scheme. Image processing electronics  96  may assess the level of focus and collimation from the pattern obtained. This airy disc pattern may suggest to the processor that the level of focus and collimation is sufficient, and thus the control electronics  96  may refrain from introducing additional correction by manipulating the secondary mirror  14 .  
      If, however, the primary and/or secondary mirrors  12 ,  14  are improperly focused or collimated, such deviations will preferably be indicated by features in the detected pattern. For example, if the primary and/or secondary mirrors  12 ,  14  are displaced from each other by too large or too small a longitudinal distance along the optical axis  20 , the image may be out of focus. A pattern representing “defocus” is schematically illustrated in  FIG. 13 . As shown, more optical energy is shifted from the central peak and into the rings as compared to the image in  FIG. 12 . Similarly, the fall-off in brightness of the rings with increasing distance from center may be replaced with other irregular variations in the brightness of the rings. For example, one or more outer rings may be more intense than inner rings.  
      If the user observes a pattern indicating that the optical system is not properly focused, the user may adjust the longitudinal position of the secondary mirror  14  along the optical axis  20 . In certain embodiments, for example, the user may use the controller  94  to translate the secondary  14  in the appropriate direction along the optical axis  20 . As described above, this process may be automated in certain embodiments. The pattern obtained may be processed to determine whether the telescope  10  is sufficiently focused and possibly to quantify the amount of “defocus.” In certain embodiments, an intensity distribution may be obtained by a camera comprising, e.g., an optoelectronic camera. In the case where the telescope  10  is focused, the intensity pattern may correspond to a narrow peak. In contrast, defocus may be indicated by broader or wider peak as measured for example by full width half maximum. The control electronics  96  may direct the actuators  36  to translate the secondary mirror  14  to or away from the primary  12 . The pattern can be monitored in some embodiments to determine when the level of focus is suitable. Other techniques can be employed as well to focus the telescope  10 .  
      In various embodiments, to collimate the telescope  10  a distant point source is imaged and a pattern is produced on the focal plane  16  of the telescope. The primary and/or secondary mirror  12 ,  14  may be canted or angled in a manner that may introduce image degradation. Light from a distant point source focused on the focal plane  16  of the telescope  10  may produce a representative pattern on the focal plane such as schematically depicted in  FIG. 14 . Skewed alignment of the primary  12  and/or the secondary  14  may, for example, cause the pattern to be elongated. In comparison with the image in  FIG. 12 , for instance, the pattern shown in  FIG. 14  is not circularly symmetric. Instead, the pattern in  FIG. 14  comprises a central bright elliptical region and elliptical rings laterally offset from this central bright ellipse. The image may also be out of focus causing the intensity distribution to deviate from the more characteristic pattern associated with the airy disc. As described above, the airy disc pattern has a generally downward fall-off superimposed on intensity oscillations that results in a set of bright rings that reduce in intensity with distance from the center.  
      To improve or correct the collimation of the telescope  10 , the secondary mirror  14  may be tipped or tilted appropriately. A user, for example, observing a pattern indicative of misalignment, such as schematically represented in  FIG. 14 , may, using the keys on the controller  94 , activate the actuators  36  to achieve suitable correction. As described above, the control electronics  96  may receive signals from the user as to which direction correction is to be introduced. The control electronics  96  may determine from the user&#39;s instructions the appropriate actuator movements to implement the suitable adjustments to the secondary mirror  14 . The user may monitor the pattern and may continue to indicate with the controller  94  the desired correction. The control electronics  96  may drive the actuators  36  accordingly. In this manner, improved collimation may result.  
      In other embodiments, the collimation process may be more automated. As described above, the pattern at the focal plane produced by the distant source may be processed to determine appropriate correction. In response to a pattern such as schematically represented in  FIG. 14 , for example, the control electronics  96  may determine how to manipulate the secondary mirror  14  to collimate the telescope  10 . The control electronics  96  may send signals to the actuators  36  to move in an appropriate manner to provide suitable tilt or tipping. In the case where the image is also out of focus, the control electronics  96  may also direct the actuators  36  to include appropriate longitudinal translation components. The pattern may be monitored to ascertain whether collimation has been achieved or whether additional correction should be introduced.  
      In various embodiments, the telescope  10  may be moved in conjunction with movement of the secondary mirror to track the celestial object used for example, during collimation. Such an arrangement may avoid losing track of the celestial object which may potentially jump out of the field-of-view with adjustments to the secondary mirror  14  made in collimating the telescope  10 . In such embodiments, for example, feedback from the actuators  36  or encoders or other components that monitor the position and movement of the secondary  14  and/or corrector  18  may be directed to control electronics that control positioning and tracking of the telescope  10 . The electronics may be employed to determine the amount and direction of object shift and may automatically introduce proper movement and suitably reorient of the telescope  10 . In various embodiments, for example, the control electronics may direct the rotating fork  112  to rotate and cant the telescope tube  38  to continue to maintain the celestial object in the field-of-view. Other configurations and approaches are possible.  
      Variations in the focusing and collimation processes may exist. Other techniques can be employed to determine whether the telescope  10  is focussed or collimated. Automation may or may not be applied to different extents and the automated systems or approaches may vary. Different types of processing may be performed as well to focus or collimate the telescope  10 .  
      Also, one skilled in the art will appreciate that the drawing in  FIGS. 12-14  are only schematic and are for illustrative purposes. A telescope  10  that is not focused and that is not properly collimated or that is misaligned may produce a pattern that includes other features as well. The actual patterns produced may vary in other ways also.  
      In certain embodiments, a heater  100  may heat the corrector  18  and/or secondary mirror  14 . Such a heater  100 , which may be useful for reducing condensation on the corrector  18  or other support structure such as optical flat or non-corrector optic, is shown in  FIGS. 7 and 8 . Preferably, the corrector cell  46  is largely separated from the telescope tube  38  and the remainder of the telescope tube assembly  40  by a substantially thermally insulating region, which reduces thermal conduction from the corrector cell  46  to the telescope tube and the remainder of the tube assembly. For example, in  FIG. 7 , the corrector cell  46  is connected to the telescope tube  38  and the reminder of the telescope tube assembly  40  via the three actuators  36 . Three point connection is provided. The actuators  36  are located about a perimeter surrounding the tube assembly  40  and corrector cell  46 . As shown in  FIG. 7 , these actuators  36  are spaced apart azimuthally about the corrector  18  by about 120° although other angles may be employed. The actuators  36  may be spaced at regular or irregular angular intervals and may be symmetrically or non-symmetrically disposed about the tube assembly  40 . Preferably, a gap separates the corrector cell  46  from the front cell  42  in these regions between the actuators  36 . This gap may be an air gap that permits tipping and tilting and other movement of the corrector  18  and secondary mirror  14  during, e.g., collimation. Alternatively, flexible and preferably thermally low conductive or insulating cover may be provided such that the corrector  18  may be tipped or tilted several degrees. Accordingly, the primary physical and thermal contact between the front cell  42  and the corrector cell  46  is through the actuator components such as the swivel yoke  72 , swivel pin  76 , and swivel pin block  82 . In certain embodiments, a component such as a dust curtain or skirt may bridge the otherwise substantially open regions between the front cell  42  and the corrector cell  46 . Preferably, however, this component is substantially thermally insulating and/or poor thermal-contact is made between this component and either the corrector cell  46  and/or other portions of the telescope  10 . Accordingly, thermal energy is not readily conductively transferred through this component (e.g., skirt or curtain) from the heated corrector cell  46  to the front cell  42  or other portions of the telescope  10 .  
      In embodiments not employing actuators  36 , the corrector cell  46  may nevertheless be substantially separated from the remainder of the telescope tube assembly  40  and heated. The corrector cell  46  may be connected to the telescope tube  38  at a limited range of points. Preferably, a plurality of connectors connect the corrector  18  to the telescope tube  38 . The plurality of connectors are preferably spaced apart around the corrector  18  and the corrector is separated from the telescope tube  38  by substantially thermally insulating regions between these spaced apart connectors. As described above, the actuators  36  may be spaced apart about the corrector  18  by intervals other than shown in  FIG. 7 . These connectors may or may not be evenly spaced about the corrector  18  and telescope tube  38  and more or less connectors may be employed.  
      Insulating regions may be disposed between the connectors. These regions may comprise air gaps or thermally insulating material or media in certain embodiments. The contact between the corrector cell  42  and the remainder of the telescope tube assembly  42  is thereby reduced. This configuration decreases the amount of thermal energy in the corrector cell  46  that is lost by thermal conduction to the remainder of the telescope  10 . The heater  100  may therefore more efficiently heat the corrector  18  (or other support structure such as optical plate or optical element supporting the secondary  14 ) as the amount and size of the heat conduction paths to the remainder of the telescope  10  is substantially reduced.  
      This heater  100  preferably provides a source of heat for the corrector  18  and possibly secondary mirror  14 . The heater  100  may comprise a heating element in thermal and physical contact with the corrector cell  46 . This heating element may be in thermal and physical contact with the corrector  18  and may be secured thereto by a variety of techniques. In some embodiments, one or more substantially thermally conducting components may separate the heating element and the corrector. In various preferred embodiments, the heater  100  comprises a resistive heater such as a heat strip, heat tape, or other type of heating element. For example, a heat strip or heating tape may be applied to a perimeter of the corrector  18 . Other methods of heating the corrector  18  (and/or possibly the secondary  14 ) may be employed as well.  
      As described above, air gaps or other thermally insulating regions preferably are disposed between the corrector  18  and/or secondary  14  and the telescope tube  36  or other portions of the tube assembly. These substantially thermally insulating regions may provide thermal insulation reducing thermal conduction from the corrector cell  46  to, for example, the front cell  42  or other portions of the telescope  10 . A substantial portion of the thermal energy will therefore preferably remain in the corrector cell  46  thereby permitting the heater  100  to more efficiently heat the corrector plate  18 . Less energy will therefore be required to heat the corrector  18  to abate the accumulation of condensation.  
      In certain preferred embodiments, where the corrector cell  46  is substantially thermally isolated from the front cell  42 , connection between the front cell and the corrector cell is provided by the actuators  36  described above. In such cases where actuators  36  control the position of the corrector  18  and secondary  14 , the controller  94  may adjust the position of the secondary to compensate for thermal shifts possibly due to thermal expansion resulting from heating the corrector and/or secondary. Other arrangements are also possible.  
      The various embodiments described herein may offer some useful advantages. Telescopes may be focused and collimated more conveniently and potentially more accurately. The user can focus and collimate the telescope  10  quicker, with less difficulty and possibly remotely. The process may also be automated in full or in part. By moving the telescope  10  in conjunction with adjustments to the secondary mirror  14 , abrupt jumps in the pattern at the focal plane that is used to evaluate collimation in certain embodiments may be reduced or avoided altogether. Accordingly, a camera such as an optoelectronic detector may be used in the collimation process. Moving the secondary  14  at the perimeter of the telescope tube assembly may reduce obstruction of light reaching the primary and thus collected by the telescope. In many telescope designs, the secondary mirror  14  and corrector  18  together weigh less than the primary  12 . Thus, moving the corrector  18  and secondary  14  together is easier than moving the primary  12 . Movement of the corrector  18  preferably causes only negligible, if any, reduction in the image quality as the corrector does not bend the beam substantially. The primary  12  can also be rigidly fixed in place, for example, with cement, epoxy, glue, or silicon couching, etc. Fixing the primary reduces shift in the image formed in comparison to designs where the primary is not securely fixed in place but moves. Disadvantageous vibration of the primary  12  may therefore be reduced. In other embodiments, the primary  12 , secondary,  14 , or corrector  18  or other support structure for the secondary, or any combination thereof can be manipulated and controlled by one or more actuators  36 .  
      While certain preferred embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims.