Jim's Unconventional Astrophotography
Autoguide Interface for Celestron Advance Series Mounts
September 22, 2003
As one begins to take their astrophotography sessions to longer exposures or small Fields of View, the accuracy of tracking with your mount becomes critical. Guiding the tracking process is an option one has to obtain sufficiently precise tracking for these more challenging images. Guiding is accomplished by taking a star - known as a guide star - and making fine adjustments to the RA rate and optionally the DEC position in order to maintain the guide star in a constant position in the field of view. constant position can be established by a cross hair or reticule for example.
Two elements are needed for guiding: 1) a means to view a star separate from your astrophotography image and 2) a means to make small adjustments to your mounts RA drive rate and optionally DEC position. The first element is accomplished through an Off Axis Guider or a guide scope. I use a guide scope; you can see my dual scope setups on my equipment page. The second element can be as simple as the slew buttons on the hand control of a motorized mount. The slew rate is generally set at or less than the tracking rate. Guiding can be done manually by pushing slew buttons in response to what you see as the position of your guide star or it can be done automatically through second camera connected to a guiding system.
The Celestron Advanced Series mounts have an autoguide port to make autoguiding very easy. Peter Katreniak has very good software that many are familiar with called K3CCDTools. This software has the ability to image with one camera and manually guide or autoguide with a second camera. He has a good explanation of the K3CCDTools guiding function on his site. Please link to his page for more details.
All images and content remain the property of Jim Thommes - copyright 2003, 2004
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