Patent Application
20140267640
This invention relates to a telescope tracking apparatus; more specifically, to an off the main optical axis tracking apparatus for attaching a CCD unit regulating movement of the telescope while a second CCD unit captures a digital image of the astronomical target desired.
In the science and hobby of astronomy, collecting data, and more precisely images, is a routine and common occurrence. Many methods and techniques are employed to achieve this. The telescope must precisely track the object being imaged or photographed, to obtain a good image with no blurs or steaks. The telescope must track an object across the night sky to keep pace with the Earth's rotation. One method used for precisely tracking an object across the night sky is to use an auxiliary camera devoted to precisely keeping the bright isophotes of a star centered on a CCD (charge coupled device) chip, or on any location on the CCD chip. The auxiliary camera must make minute changes to the telescope's position correcting for drift, motor mount tracking errors, etc. What may seem like a trivial, job, locating a “guide star” to be used for tracking purposes, which must be in close proximity to the object being imaged, is not at all trivial. In fact, more time can be spent looking for suitable guide stars than actually imaging.
There are a few methods for precisely tracking a guide star. One method is to use a smaller telescope affixed to the top of the main telescope. In this way, the user has two telescopes, one for imaging, and one for guiding. Another method utilizes a CCD camera having two CCD chips, one large CCD chip for imaging and an adjacent smaller CCD chip for guiding the telescope on a star. Both methods have pros and cons.
Yet another method useful for finding guiding stars for tracking purposes, is the use of a device called an off-axis guider. Off axis guiders are well known in the field. All off-axis guiders employ a prism or a pick off mirror to divert a small portion of the light from a telescope to an eyepiece or camera of some type.
Off-axis guiders offer a few important advantages over a dedicated guide scope, or a dual CCD chip camera. Off-axis guiders are more affordable than either a guide scope or dual chip camera. An off-axis guider can be placed almost any where in the optical train, more importantly in front of colored filters, which a dual chip camera cannot do. This alone has serious drawbacks for a dual chip CCD camera. An off axis guider will not suffer from differential flexure which sometimes can occur when using a separate guide scope. Moreover, an off-axis guider can obtain more precise tracking of the desired astronomical object than a separate guide scope.
The proposed off-axis guider described herein, is a unique and novel device, having several critical, essential features designed to make locating guide stars easier.
Currently, there is no off axis guider that has a controlled rotating prism, and or that can move in or out of the optical axis, made for small amateur telescopes.
The off-axis guider of the present disclosed embodiment is a newly designed off-axis guider. This apparatus features a right angle prism that can rotate about the telescope axis; and, travel in or out of the optical axis. Also the off-axis guider of this application has a built-in focuser for the auto-guiding CCD camera. The off-axis guider disclosed herein may be constructed from aluminum or any other metal or material as desired.
Rotation around the optical axis is achieved by the use a knob, attached to a screw. The screw acts upon a matching gear. The gear is attached to the body that holds the guiding camera port. The guiding port can be raised or lowered, in or out of the optical axis by the use of a threaded ring that engages a thread. The thread on this guide port is fixed and cannot rotate, and since the ring is turned around the fixed non-rotating guiding port, it moves the guiding port up or down raising or lowering the prism in or out of the optical axis allowing more photons to reach the main CCD camera, thereby improving the images obtained.
It is this same manner that is used to bring the auto-guiding camera into focus. Locking thumbscrews are used to secure all moving parts when a guide star is found and focused.
The off-axis guider of this application can be fabricated with threads on the front and rear of the unit, or have a smooth inside diameter with perpendicular set screws, to allow the attachment of the off-axis guider assembly to a telescope or camera.
Any worm or worm gear or other gearing mechanism can be used. Placement of gear or worm on either the outside or housed inside of the unit without departing from the spirit of the invention. Movement of the prism in or out of the optical axis can be either a screw type arrangement or a sliding mechanism. Focusing can also be a screw type or a sliding mechanism. All of these alternatives are well known in the telescope fabrication art.
Motors can be attached to any motion of the off-axis guider. Bearings can be employed anywhere as desired, although are not required for smooth operation of the moving elements of this device.
The off-axis guider assembly can be made to offer 1, 2 or 3 axes of controlled motion. The prism can rotate around the optical axis. The prism can move in or out of the optical axis. The auto-guiding camera can be brought into focus.
This is an application of an off-axis guider assembly and methods and use of the assembly on a telescope.
The present invention relates to a new and non-obvious assembly that can be used to provide an off-axis guide for astronomical viewing which tracks guide celestial bodies, such as guide stars, automatically and which can be skewed automatically by computer controlled devices. The axis of viewing can be changed dynamically to keep the tracking of the astronomical scene under investigation to allow time-extended astronomical photography to be accomplished easily and economically.
An off-axis guider assembly is made from an adapter connected to a telescopic instrument; an off-axis guider body attached to the adapter attached to the telescopic instrument; a connector interposed between a photographic assembly comprised of an filter wheel and a camera; and, a worm-gear mechanism for moving the off-axis guider body around the circumferential axis of the optical axis connected to an auto-guiding guide camera.
The off-axis guider assembly can also provide an off-axis guider comprised of a secondary camera useable for guiding a telescope. The off-axis guider assembly can also provide a right-angle prism while permitting the passage of viewing to be passed to the primary focus of the camera having a principal focus of the telescope.
An off-axis guider assembly provides a fixed body; a rotating piece cooperating with the fixed body; a moveable prism attached to the rotating piece for moving a prism into and out of an optical axis of a telescopic instrument; and, a worm gear for moving the rotating piece around the axis of the optical axis of the telescopic instrument.
The off-axis guider assembly can further comprise a focus ring for moving a guider assembly auto guider around the perpendicular axis of the off-axis guide assembly and a worm gear controlled by a computer-assisted stepper motor to track the movement of a guide celestial body.
A method of installing an off-axis guider assembly on a telescopic instrument comprising the steps of inserting an adapter on the telescope; attaching the off-axis guider assembly to the adapter providing an off-axis auto-guiding camera to the assembly; attaching an adapter to a filter wheel of an CCD camera; and, attaching the CCD camera to the adapter.
A method of using an off-axis guider assembly on a telescopic instrument for photographically capturing the image of a celestial object can also comprise the steps of determining an appropriate guide point; focusing an auto-guiding camera on the appropriate guide point; activating the auto-tracking element of a CCD camera to follow the appropriate guide point; and, initiating the tracking and capture of the desired image of the celestial object with the CCD camera using the off-axis guider to skew the camera to maintain the focus of the camera.
By establishing the auto-guiding camera on the perpendicular axis and intercepting a portion of the optical viewing made by the telescope, as the auto-guide camera moves it tracks the fixed position while allowing movement of the CCD camera to move the CCD in fixed relationship to the celestial object under study, permitting the clearest view and capture of the object on the CCD plate. In manual installations, viewing the guide and maintaining the image in the cross hairs of the guide camera on the object do this. This can also be done automatically sending a skewing coordinates to the CCD camera focusing arrangement.
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The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in size, shape and material as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.
