Practical Amateur Astronomy by Michael A. Covington

Author:Michael A. Covington [Covington, Michael A.]
Language: eng
Format: epub
Publisher: Cambridge University Press

9.5.2Subpixel Accuracy

Crucially, the autoguider – whether a standalone device or software in a laptop – analyzes star images with subpixel accuracy. It doesn’t just figure out which pixel in the guiding camera corresponds to the star image. It analyzes how the light is spread over several pixels and finds the centroid of the image relative to several pixels: “15% of the way from this one to that one,” for instance.

That means the guidescope and guide camera do not need to have the same resolution as the main telescope. If the pixels in the guide camera and main camera are about the same size, the guidescope can be as short as 1/5 the focal length of the main telescope. Even smaller guidescopes, as in Figure 8.3, are sometimes successful.

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