Optical: systems and elements – Compound lens system – Telescope
Reexamination Certificate
1999-10-25
2003-05-13
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Compound lens system
Telescope
C359S399000, C318S266000, C318S625000
Reexamination Certificate
active
06563636
ABSTRACT:
RELATED APPLICATIONS
This patent application is related to co-pending patent application entitled UPGRADEABLE TELESCOPE SYSTEM and to co-pending patent application entitled FULLY AUTOMATED TELESCOPE SYSTEM WITH DISTRIBUTED INTELLIGENCE, both filed on instant date herewith and commonly owned by the Assignee of this patent application, the entire contents of both of which are hereby expressly incorporated by reference.
FIELD OF THE INVENTION
The present invention relates generally to telescopes, such as those commonly used for observing/photographing celestial objects. The present invention relates more particularly to a telescope system having an intelligent motor controller for accurately controlling telescope position and for precisely controlling the speed at which the telescope moves to facilitate tracking of celestial objects therewith. The present invention further comprises an optical encoder using two photodetectors operating in quadrature to provide enhanced servo control for the telescope positioning motors, a calibration circuit for assuring reliable operation of the encoder with LED's having varying brightness characteristics and/or varying sensitivities of photodetectors and a rotatable mount which provides electrical communication to an altitude drive motor located in a fork thereof while mitigating problems due to undesirable wrapping of a power/control cable about the mount as the mount rotates.
BACKGROUND OF THE INVENTION
Telescopes for observing and/or photographing celestial objects such as planets, moons, stars, galaxies, asteroids, comets, nebulae, and the like are well known. Such telescopes range in size from small, readily portable ones to large fixed ones which are permanently located in observatories. The smaller telescopes are commonly used by students, hobbyists, and amateur astronomers. The larger telescopes are generally only used by researchers and professional astronomers.
Common types of telescopes include refractor telescopes, reflector telescopes, Schmidt-Cassegrain telescopes and Maksutov-Cassegrain telescopes. Refractor telescopes have a light collecting objective lens which focuses the collected light upon an eyepiece. The eyepiece, in cooperation with the objective lens, provides the desired magnification.
A reflector telescope utilizes a primary mirror to collect light and a secondary mirror to reflect the collected light through an opening in the telescope tube to an eyepiece. The eyepiece is mounted upon the tube, typically near the front of the tube, and is positioned orthogonal to the tube. The eyepiece cooperates with the primary mirror to provide the desired magnification.
Schmidt-Cassegrain telescopes are similar to reflector telescopes, except that the secondary mirror of a Schmidt-Cassegrain telescope reflects the collected light through an opening in the primary mirror instead of through an opening in the tube. In this manner, the eyepiece can be located directly behind the primary mirror, which is convenient for some types of viewing and photography. Additionally, light enters a Schmidt-Cassegrain telescope through a thin, two-sided aspheric lens, known as a correction plate. Further, the secondary mirror is convex, so as to increase the effective focal length of the primary mirror.
Maksutov-Cassegrain telescopes are similar to Schmidt-Cassegrain telescopes, except that in Maksutov-Cassegrain telescopes light enters the telescope through a meniscus lens and an oversized primary mirror is used to provide an unvignetted field of view.
In viewing celestial objects with any type of telescope, it is necessary to continually move the telescope, so as to maintain the telescope in desired alignment with the celestial object. This is necessary to compensate for the rotation of the earth with respect to the cosmos. Thus, such continual realignment of the telescope maintains the desired celestial object within the field of view of the telescope as the earth rotates about its axis.
Smaller, portable telescopes of the reflector, refractor, Schmidt-Cassegrain, Maksutov-Cassegrain or any other desired type are typically mounted upon a tripod to facilitate portability and use of the telescope upon uneven outdoor surfaces, such as upon the ground, upon paved surfaces, such as roads or parking lots, or upon any other desired surface.
Two different types of mount, altitude azimuth and equatorial, are commonly used to removably attach a telescope to a tripod. Altitude azimuth (alt-azimuth) mounts provide a comparatively rigid and steady mount for the telescope, but are more difficult to maintain in alignment with the desired celestial object when the telescope is being aimed manually. Altitude azimuth mounts have only two perpendicular axes of rotation, which make the altitude azimuth telescopes inherently more rigid and stable than equatorial telescopes. The altitude axis of rotation allows the telescope to pivot with respect to the mount about an horizontal axis and the azimuth axis of rotation allows the telescope to pivot about a vertical axis. In order to maintain alignment of a telescope having an altitude azimuth mount with respect to a desired celestial object, it is generally necessary to move the telescope about both the altitude and azimuth axes, since the position of celestial objects generally varies in both altitude and azimuth as the earth rotates.
Equatorial mounts facilitate easier maintenance of alignment of the telescope with a desired celestial object, since the telescope must only be moved about a single axis so as to maintain such alignment. In an equatorial mount, two orthogonal axes are configured such that one of the two axes can easily be aligned so as to be parallel to the axis of rotation of the earth. Once such alignment with the earth's axis of rotation is accomplished, then it is merely necessary to move the telescope about the other axis, so as to maintain alignment of the telescope with a desired celestial object. Thus, with an equatorial mount only a single axis of the telescope needs to be moved in order to maintain such alignment.
However, in an equatorial mount it is necessary to provide two additional orthogonal axes of alignment (similar to those of an altitude azimuth mount) in order to facilitate alignment of one axis so as to be parallel to the earth's axis of rotation. Thus, an equatorial mount actually comprises an altitude azimuth mount plus two additional axes and thus has a total of four different alignment axes. Because the equatorial mount comprises four different alignment axes, and because each axis inherently decreases the stability of the mount, it is difficult to manufacture an equatorial mount which is as stable as a comparable altitude azimuth mount (which has only two axes of alignment).
However, although such contemporary telescopes have proven generally useful for their intended purposes, they do possess deficiencies which detract from their overall effectiveness. For example, motorized telescopes frequently lack the precision required to reliably locate (under computer control) more faint celestial objects when higher magnifications are utilized. Thus, it is frequently necessary to make tedious manual adjustments in order to locate a desired celestial object and to position the desired celestial object within the center of the field of view of the telescope.
It is desirable to provide a motorized telescope system having sufficient accuracy to generally locate celestial objects of interest without requiring excessive manual adjustment of the telescope.
Further, many motorized telescopes are incapable of accurately tracking a celestial object (again, under computer control) as it moves across the sky due to the earth's rotation. While motorized telescopes frequently do provide some tracking capability, it is often not sufficiently accurate to facility celestial photography. Frequently, such tracking is accomplished by merely stepping the telescope drive motors when the position of the telescope has been determined to be substantially out of alignment with the desired ce
Baun Kenneth W.
Dewan Stanley H.
Tingey Brian G.
Fineman Lee A.
Meade Instruments Corp.
Spyrou Cassandra
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