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Old 18-01-2013, 07:15 AM
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gregbradley
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Join Date: Feb 2006
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Quote:
Originally Posted by alistairsam View Post
Hi,

Is there a sweet spot or optimum range for image scales in a guiding system that provide the best autoguiding?
eg. many use the finder guider where at a 200mm FL and a camera like the qhy5, the image scale is 5.4 odd arcsec/pixel.
would it be beneficial to use a longer FL guidescope with the same camera and if so are there any guidelines or numbers that help determine the optimum guidescope FL?

Have a look on the SBIG site. There is an article discussing this regarding the lens attachment available for the STi guider.

Short answer is short focal lengths for guide scopes work well as it makes it easy to get a guide star and software uses sub pixel accuracy in guiding.

Although AstroPhysics guide scope is about 900mm as I recall.

Greg.
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