Manually indexed adjustable focal length planetarium

A dome surface includes patterned perforations which allow light passing through to form various star constellations on a separate external surface. The dome rests upon a base which houses both a light source and a lens system, which may be adjustable, to control the spread of light. The base also has a compass attached to it for the purpose of orienting the planetarium to the actual direction of "true North." A tap player might also be attached to the base of offer recorded instructions. Above the dome there can be placed an opaque mask which blocks the light coming through most of the dome perforations while allowing light to be projected only through one or several sets of perforations which represent selected star constellations. A support placed under one side of the planetarium base tilts the planetarium to an angle corresponding to the local latitude.

DESCRIPTION 
BACKGROUND OF THE INVENTION 
1. Technical Field 
My invention relates to celestial learning tools or planetariums and in 
particular to a small planetarium which is manually adjusted and indexed. 
2. Background Art 
Most planetariums are very large complex systems requiring motor driving 
means with single or multiple axes of rotation to simulate apparent 
changes of the constellations in the sky due to the earth's rotation 
around the sun. 
Many other planetariums require a projecting surface spaced at a specific 
distance from the light projection source for proper focusing of the 
celestial configurations. 
Other planetariums provide complex systems needed for blinking means or 
additional light systems for pointing out specific configurations of 
heavenly bodies in a planetarium display. 
DISCLOSURE OF INVENTION 
The present invention provides an extremely simple and inexpensive means of 
displaying the constellations of a hemisphere in proper diurnal positions 
with a manually operated rotatable dome containing perforations patterned 
so that projected light through the perforations forms constellation 
configurations on separate external surfaces. The dome has a protruding 
combination handle and pointer, and is mounted rotatably on a base 
provided with a compass for proper orientation. The base is marked with 
indexed points for the days of the year so as to bring the planetarium 
orientation of the constellations into alignment with the actual apparent 
stellar configuration for the day marked by the pointer. 
At least one lens mounted between an internal light source and the 
perforated dome provides control over the spread of light. The focal 
length of the constellations in the dome may be adjusted by moving the 
planetarium relative to the external surface or by moving an adjustable 
lens system to focus the constellations onto a separate external overhead 
and/or wall surface at a variety of distances from the dome. 
Each of a series of masks fits over the dome and is secured thereto by a 
protruding tab containing a shaped opening, so that it can be secured to 
the dome indicator tab, causing the mask and dome to rotate together. 
Each mask is perforated with at least one shaped opening of a particular 
configuration to allow the light projections of a single constellation to 
project therethrough to limit the stellar display and to single out one or 
more constellations in particular. 
A sound recording means attached to the base of the present invention 
provides the sound instructions for operational and educational 
information about the constellations projected visually by the 
planetarium. 
A support leg may be placed under one side of the planetarium base to tilt 
the planetarium relative to a horizontal surface at an angle corresponding 
to the local latitude.

BEST MODE FOR CARRYING OUT THE INVENTION 
In FIG. 1 the dome 20 is a perforated opaque shell and can be of any 
uniformly curved shape, including a hemisphere. The dome is preferably 
manufactured from any molded synthetic plastic material. The dome's 
peripheral edge 25 is slightly flattened so as to permit easy engagement 
between a top ring 24 and a bottom ring 39 to form a track to engage the 
base. 
As shown in FIG. 3, there is located an indicator tab 26 at one point on 
the peripheral edge 25 of the dome. The tab can be made of molded or 
extruded plastic and heat staked to the dome edge protruding above the 
peripheral edge. The tab extends outwardly beyond the edge for easy manual 
grasping, and tapers, terminating in a point. 
Through the dome shell, there are various perforations 22 which are 
positioned in configurations to simulate star constellations. The location 
of these perforations is calculated to coincide with the actual relative 
location of various celestial configurations. As is well known in the art 
of astronomy, the position of star systems as viewed from one earth 
location changes on a predictable, daily basis. Therefore, the position of 
the perforations on the dome 20 are calculated so that as the dome is 
rotated by measured degrees, the projections of light through the 
perforations also rotate, thus simulating the daily appearance of 
celestial bodies on surfaces exterior to and surrounding the dome. 
A light source 27 within the base 40 emits light rays that pass outwardly 
through a focusing lens 30, and then through the perforations 22. Several 
focusing lenses might be used. The resulting light emissions form images 
of the star systems upon any separate exterior surface, such as the 
ceiling and walls of a room. 
In FIGS. 1-3, the dome 20 is slidably supported upon the top support 
surface 32 of the base 40. This support is accomplished by first 
positioning inside the base a flat bottom ring 39, of a larger 
circumference than the circumference of the peripheral edge 25 of the 
dome. The dome is then placed on top of the bottom ring and the base so 
that the peripheral edge 25 aligns with and is spaced interiorly of the 
base edge and rests upon a portion of the bottom ring 39 along the entire 
circumference of both the edge and the bottom ring. The top ring 24, 
having the same circumference as the bottom ring 39 is then placed over 
the peripheral edge and the base, thereby opposing the bottom ring in the 
same position relative to the peripheral edge 25. The top ring, peripheral 
edge, and bottom ring can be fastened together by bolts, screws or heat 
staked plastic pegs 76 extending from and through the top ring to the 
bottom ring, sandwiching the peripheral edge of the dome therebetween. In 
this manner, the rings and dome 20 will form a track with the base edge 33 
slidably fitting between the rings and will be rotatable on the base edge. 
The space between the top and bottom rings which is exteriorly adjacent to 
the peripheral edge 25 of the dome forms a track or cavity in which the 
base rim 33 will rotate freely. Thus, the ease with which the dome is 
manually rotated eliminates the need for any motor driving means. 
The base rim 33 of the top support surface 34 is formed by the support 
surface's circular inner edge. The rim is situated between the top and 
bottom rings spaced apart from the peripheral edge 25. The rim 33 has a 
thickness less than the distance between the top and bottom rings, so that 
the dome track will rotate on the rim. 
Extending outwardly from the base rim 33 is a top flat surface upon which 
are printed or engraved sequential markings 34 which represent days in a 
yearly calendar. The indicator tab 26 will be selectively positioned 
opposite one of these markings. When the tab 26 is held and rotated, the 
connected dome and the perforations therein also rotate. In this manner, 
the tab's alignment with a selected diurnal marking will result in the 
projection on a surrounding surface of the corresponding celestial 
configuration for that particular date. The tab thus serves at least two 
functions in that it is both a handle for rotating the dome and also a 
means for indicating which diurnal star configuration is projected for any 
given day. 
In FIG. 2 the base 40 houses a light source 27, such as an incandescent 
lamp. The light rays will shine against the interior surface of the dome, 
continuing through the dome at the perforation sites 22. Power for the 
lamp may be supplied by typical internal means such as batteries 28 
depicted in FIG. 2, which in turn are wired to the lamp socket 46. 
Alternatively, the lamp could of course be connected to a suitable 
external power source in any well-known manner. 
The spread of light through the perforations is controlled by at least one 
lens 30 situated above the light source 27. The lens could be stationary 
or attached to the top of a movable lens casing 75. The lens casing is in 
turn slidably engaged to a lens housing 77. The exterior of the sides of 
the casing are threaded. This threaded surface adjustably interacts with a 
matching threaded surface located on the surface of the interior sides of 
the lens housing. An adjustable lever 38 comprises a shaft which extends 
from the upper threaded portion on one exterior side of the lens casing, 
upwardly and outwardly through a slot in the side of the base's top 
support surface. Lateral movement of the lever in one direction will cause 
the connected thread surface to rotate in one direction, thereby movably 
engaging the lens casing 75 vertically in one direction. Movement of the 
lever in the opposite direction would of course change the vertical 
direction of the lens casing, thereby adjusting the lens 30 in its 
position relative to the light source 27. The distances between each 
thread on all the threaded surfaces is sufficiently large so that a 
relatively small movement of the lever 38 will cause the lens casing 75 to 
rise or descend in disproportionately larger degrees. This will permit 
quick adjustment of light divergence through the lens: the focal length 
can be adjusted to redefine the "real image" of the star constellations 
when the ceiling height or shape is changed. With a stationary lens the 
focal length of the constellation projections may be adjusted by moving 
the entire planetarium. 
A mask 12, is shaped to fit over and subsequently conform to the exterior 
surface of the dome, as depicted in FIGS. 1 and 5. Each mask preferably 
comprises a thin shell fabricated from any light weight, opaque material. 
Alternatively, light-transmissive materials such as various inexpensive 
plastics could be used if they are first painted with a coating which will 
not transmit light. 
The mask will be provided with at least one patterned opening 14 which 
conforms in shape and size to one of the constellation configurations on 
the dome surface to admit through the mask all of the light rays 
corresponding to stars in the constellation. Many different masks could be 
interchangeably used, each having only one or more shade openings which 
correspond to a particular constellation. 
Best seen in FIG. 4, protruding from one point on the edge of the mask is 
located a "mask connecting tab" 16 which will align with the dome 
indicator tab 26 when the mask's openings coincide with the perforations 
22 on the dome. The mask 16 is provided with a mask tab opening 18 having 
the approximate shape of the perimeter of the indicator tab. Thus, the 
mask tab will fit over the indicator tab, and the protrusion of the 
indicator tab through the opening 18 will removably lock the mask to the 
dome so that both rotate simultaneously when the indicator tab 26 is 
moved. In this manner, light emissions can be limited to projections of a 
single constellation onto the separate external surface. The image of the 
constellation can be further accentuated by adjusting the lens to refocus 
the light rays through the smaller number of perforations, rather than 
through the multitude of perforations being utilized when a mask is not in 
use. When the user desires to emphasize a different star system, he/she 
can simply remove one mask and replace it with a mask which includes an 
opening corresponding to that particular star system. Thus third and 
fourth functions for the dome tab are indicated as an orientation and a 
locking means for the mask. 
A compass 36 or other direction-locating means is affixed at one point on 
top of the top support surface 32. The compass is preferably situated 
adjacent and exterior to the diurnal markings 34. As the base is rotated, 
the compass needle will continue to align itself with magnetic north, and 
orientation of the needle relative to the underlying compass scale (marked 
in degrees) will indicate the direction in which the base is pointed. This 
compass attachment will permit the user to duplicate more exactly the 
orientation of the simulated stellar display to that of the actual 
celestial configuration on any given evening. For instance, on a given 
night, a particular constellation would be located in the sky in a 
particular orientation, relative to the viewer. The viewer would orient 
the base so that the compass needle on the planetarium base pointed to the 
correct "North" indication, and then he/she would rotate the indicator tab 
so that the tab pointed to the diurnal marking for the date. Thus, the 
simulated constellation would be projected onto the ceiling in the same 
orientation that the actual constellation would appear in the sky on that 
date. After observing the projected celestial display, a viewer could then 
go outside and easily point out and identify all of the visible star 
systems. Two night later, when the reference constellation has moved 
several degrees, the indicator tab can be rotatably shifted to the 
corresponding diurnal marking, and the true celestial configuration for 
that night will again be visible on the overhead projecting surface. 
A sound recording and playing means 50, such as a cassette recorder, may be 
attached to the base 40 at one of its external sides. The recorder then 
plays a tape which provides a lecture on the various stellar displays 
projected onto the ceiling. The tape would also provide operational 
directions concerning the use and adjustment of the planetarium. The 
recorder may be powered by the power source 28, or could be directly 
connected to a household electrical outlet. The "on/off" switch for the 
recorded might be incorporated into the on/off switch 41 for the light 
source, so the activation of the light source will simultaneously activate 
the cassette recording. Alternatively, the recorder could be provided with 
a separate on/off switch. 
In FIG. 6 an alternate embodiment provides a support 60 or leg to be placed 
under one side edge of the planetarium base 40 for tilting the planetarium 
to an angle 62 from the horizontal surface 64 upon which it rests. The 
angle would correspond to the local latitude so that the projection on the 
ceiling and wall would coincide exactly with the appearance of the 
constellations in the sky if the ceiling and wall were removed. Adjustment 
of the angle 62 for different latitudes may be accomplished by tilting the 
support angle, providing various length supports or by an adjustable, such 
as telescoping, support. Leg 60 swivels flat against base 48 (dashed). 
Educational value, ease of use, convenient adjustment techniques, and 
simplicity of fabrication are just some of the features which make this 
planetarium a very useful instrument for the amateur stargazer. 
It is understood that the preceding description is given merely by way of 
illustration and not in limitation of the invention and that various 
modifications may be made thereto without departing from the spirit of the 
invention as claimed.