Fixed-star projecting machine for planetarium

A fixed-star projecting machine for a planetarium includes a fixed-star projection lens unit in each polygon of the globe surface of a fixed-star projection globe divided into a plurality of parts. Of these projection lens units, one whose projection range covers both sides of the equator is adapted to have its optical axis shifted in the direction which increases the attaching angle. The star positions of the fixed-star negative of the shifted projection lens unit are corrected to the normal projection positions according to the amount of shift.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to a fixed-star projecting machine for a planetarium 
which uses a small-diametered projection globe to make it possible to 
project not only stars with improved image formation but also 
constellations, marks and constellation pictures. 
2. Prior Art 
The conventional planetarium apparatus disclosed in U.S. Pat. No. 3,571,954 
projects fixed stars by using a combination of single-sleeve type 
projectors for projecting stars of the first and brighter magnitudes 
embedded in a globe and a pin hole type projector with many apertures 
formed on the surface of the globe for projecting other stars. 
With this projecting method, however, to improve the images of stars 
projected by the pin hole type projector, not only is it necessary to 
enlarge the globe, but also there is a limit to the number of lens type 
projectors that can be attached to the globe surface and to the number of 
auxiliary parts such as electrically conductive springs for feeding power 
to lamps for said projectors. Further, if the globe is reduced in 
diameter, the images of stars projected by the pin hole type projector 
will be inferior in image formation to the images of brighter stars 
projected by the single-sleeve type projectors. Thus, only a very 
disharmonius pattern of images of stars projected could be formed on the 
whole heaven, and there is almost no space available for installing the 
single-sleeve type projectors and their accessories so that the bright 
stars must be projected by the pin hole type projectors which are inferior 
in image formation to single-sleeve type projector. 
SUMMARY OF THE INVENTION 
This invention is intended to eliminate the drawback described above. An 
object of the invention is to provide a fixed-star projecting machine for 
a planetarium wherein the projection of stars is effected by a lens type 
projector with improved image formation and a portion of the projected 
image is not obstructed by auxiliary parts such as electrically conductive 
slip rings disposed on a great circle of the globe. 
This invention is a planetarium wherein a fixed-star projection globe 
having auxiliary parts disposed along one great circle of the globe is 
rotated by the rotary motions about a rotary axis extending at right 
angles to said great circle to project the fixed stars in the whole 
heaven, characterized in that the globe surface of the fixed-star 
projection globe is divided into a plurality of regions, in each of which 
a projection lens unit is provided. Each of the lens unit includes a 
condenser lens, a fixed-star negative having stars in a star region 
corresponding to the region, and a projection lens is disposed on the same 
radial line with respect to a light source disposed at the center of the 
fixed-star projection globe, those projection ranges extending across the 
great circle of said globe are so arranged that the optical axes of the 
projection lenses are disposed at positions shifted from the centers of 
the respective regions toward the rotary axis, the other units being so 
arranged that the optical axes of the projection lenses coincide with the 
respective centers of their regions, the star positions of the fixed-star 
negatives of the projection lens units whose optical axes are shifted 
being corrected according to the amount of shift of the optical axis so 
that they come to the normal projection positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIGS. 1 and 2, a fixed-star projection globe 1 is formed of two globe 
halves 1a and 1b divided along a great circle 1c. It can be rotationally 
driven about a first rotary axis I perpendicular to the great circle 1c, a 
second rotary axis II horizontally extending through the center of the 
great circle 1c, and a third rotary axis III vertically extending through 
the intersection between the first and second rotary axes I and II. 
The globe surface of the fixed-star projection globe 1 is provided with a 
required number of projection lens units 3 adapted to project the fixed 
stars in the whole-heaven using a single fixed star projection light 
source 2 housed in the center of the globe. Installed in the space between 
these units 3 are a plurality of auxiliary projection units 4 for 
projecting constellations, marks and constellation pictures using their 
individual light sources 5. 
Each projection lens unit 3 comprises condenser lenses 3a, fixed-star 
negative 3b, and projection lens 3c and projects the fixed stars in one of 
the angular ranges into which the whole heaven is divided. In the case of 
the lens projection type, from the standpoint of optical performance and 
the size and projection efficiency of the fixed-star projection globe 1, 
the whole heaven is divided into 32 parts by regular pentagons and 
irregular hexagons whose circumscribed circles are same size so that the 
respective projection ranges of the projection lens units 3 are the same 
(the projection angle with respect to the center is 22.degree.41'). For a 
better understanding of this, FIG. 3 shows a plan view in which the 
dividing surface of the fixed-star projection globe 1 is taken as the 
equator and a half of the celestial sphere is divided into sixteen parts; 
however, it is not absolutely necessary to take the dividing surface as 
the equator provided that a regular pentagon is located at the zenith and 
that the corresponding coordinate transformation is effected. 
The globe halves 1a and 1b are provided at their coupling portions with a 
bearing 6 for rotating the fixed-star projection globe 1 about the first 
rotary axis I. The fixed-star projection globe 1 is rotated about the 
first rotary axis I by an unillustrated gear meshing with a gear 7 (see 
FIG. 4) which is installed around the outer periphery of either of globe 
halves 1a and 1b. The fixed-star projection globe 1 is held by an annular 
holder 8 formed of an inner ring 9 and an outer ring 10 and an 
unillustrated rib connecting the rings 9, 10 through the bearing 6. 
Further, the annular holder 8 is supported along the second rotary axis 
II, by horizontal shafts 11 which are provided with the bearing 6 at one 
of their respective ends and are rotatably supported by bearings 13 in 
support members 12 erected on a base plate 14. Thus, the fixed-star 
projection globe 1 is rotated about the second rotary axis II. The base 
plate 14 has a vertical shaft 15 rotatably supported in a bearing 16 to 
rotate the fixed-star projection globe 1 around the third rotary axis III. 
Each auxiliary projection unit 4 comprises a condenser lens 4a, projection 
negative 4b and projection lens 4c. Supply of power to the light sources 5 
is effected through a required number of slip rings 17 disposed around the 
axis I on the upper surface of the annular holder 8, and then through 
brushes 18 fixed to the fixed-star projection globe 1 in contact with said 
slip rings 17, a required number of slip rings 19 disposed on the surfaces 
of the horizontal shafts 11, and brushes 20 in contact with said slip 
rings 19. The annular holder 8 has a drive mechanism (not shown) for 
driving the gear 7 (see FIG. 4) and position detecting means (not shown) 
installed in an inner space 21, and is provided with a cover 22 (see FIG. 
4) over said slip rings 17. 
In FIG. 3 in which a half of the celestial sphere is divided into sixteen 
regions by regular pentagons and irregular haxagons, and each divided 
region has the above described projection lens unit 3. In order for five 
irregular hexagons provided adjacent the equator H to extend their 
projection ranges across the equator (with a declination of 0 degree) H to 
the other hemisphere (the hatched areas indicate projection portions to 
the other hemisphere), each projection lens unit 3 is disposed at a 
position Q' which is shifted from a center of a circumscribed circle of 
the hexagon Q toward the first rotary axis I. More concretely, the 
declination of the center Q is +10.degree.49 whereas the declination of 
the shifted position Q' is greater than that of the center Q, e.g., 
+12.degree.49. At this shifted position, a luminous flux 23 from the lens 
unit 3 advances to the other hemisphere, i.e, to the southern heaven 
without being obstructed by the cover 22 of the annular holder 8 and other 
obstructing elements (see FIG. 4). 
On the other hand, the position lens units 3 provided in said divided 
regions excluding said five irregular hexagons are positioned at the 
centers P, Q of the circumscribed circle of them. 
Said projection lens units 3 provided in the respective region are so 
arranged that a line connecting a center O of the fixed-star projection 
globe 1 to P or Q or Q' coincides with the optical axis X--X of the lens 
units 3 (see FIG. 5). 
And the fixed-star negatives 3b of the projection units 3 are so arranged 
that projected images of the fixed stars come to the proper positions of 
themselves in a star field. 
Thus, the fixed-star projection globe 1 having thirty-two projection lens 
units 3 project the fixed stars in the whole celestial sphere without 
being obstructed by the auxiliary parts disposed along one great circle of 
the globe 1. 
In addition, if the auxiliary projection units 4 attached to the fixed-star 
projection globe 1 or the slip rings 17 disposed on the annular holder 8 
are required to be increased in number, it is advisable that a second 
annular holder 8a of less thickness be provided outside the annular holder 
8 to increase the outer diameter and that electrically conductive slip 
rings 19 be disposed on the surface thereof (see FIGS. 4 and 5). 
If the apparatus of the aforesaid arrangement, together with a planet 
projecting machine 1A arranged as shown in FIG. 8, is positioned at the 
center of a dome (see FIG. 7), the diurnal motion and latitude variation 
of fixed stars as seen on the earth can be reproduced by rotary motions 
about the axes I and II, respectively, while the diurnal motion of fixed 
stars as seen on a planet and the precession of the earth can be 
reproduced by rotary motions about the axes I, II and III. 
In the present invention, each polygon by which the globe surface of the 
fixed-star projection globe 1 is divided has only one projection lens 
unit; thus, as compared with the case of using a conventional pin hole 
type fixed-star projection globe, a large number of spaces for attaching 
the auxiliary projection units 4 can be secured. For example, if the 
projection lens units 3 of the invention are installed in a fixed-star 
projection globe 1 whose outer diameter is 1 m, then 100 or more auxiliary 
projection lens units 4 can be attached. 
This invention relates to a planetarium for projecting the fixed stars in 
the whole heaven by the rotary motions of the globe around the rotary 
axis, wherein each of the polygonal surface of the fixed-star projection 
globe divided into a plurality of parts is provided with a projection lens 
unit respectively. Each of the projection lens units includes the 
condenser lens, fixed-star negative and projection lens, and those 
covering both sides of the great circle have their optical axes shifted in 
the direction which increases the attaching angle, and the star positions 
in the fixed-star negatives of the shifted projection lens units are 
adjusted according to the amount of shift so that they come to the normal 
projection positions. Thus, according to the present invention, fixed 
stars which had been incapable of projecting because of the provision of 
auxiliary projection units for projecting constellations, marks and 
constellation pictures in a conventional fixed-star projecting machine can 
now be projected with improved image formation. Further, the present 
invention can also eliminate the inconvenience of having to provide 
separate projection units at positions away from the equator in the case 
of projecting important stars in the vicinity of the equator by the 
conventional planetarium having pin hole type projector.