A science frame autoguiding and image alignment algorithm with sub-pixel precision, capable of guiding on defocused stars.
We operate and have access to several telescopes (NGTS, NITES, Warwick 1m, 1.5m San Pedro Martir) that require precise autoguiding. Sometimes we must defocus the telescope for various reasons, but we'd still like to autoguide. Donuts was designed to allow this. It had to be simple, fast and accurate. It works well as an autoguiding algorithm for equatorial telescopes (no field rotation).
The process for aligning apertures for photometry is essentially the reverse. Rather than correcting the telescope pointing, the apertures must track the drift of the stars. Donuts can therefore be used to track the stellar positions for CCD photometry also.
The algorithm has its limitations. It currently does not deal with rotation and large drifts, where the field moves by approx. half a FOV or more. Our paper describing the details can be found here:
http://adsabs.harvard.edu/abs/2013PASP..125..548M
This package is currently pre-alpha. We don't recommend using it just yet :)
MIT License
Copyright (c) 2016 James McCormac & Simon Walker
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