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arXiv · 2201.12466

A Fourier method for the determination of focus for telescopes with stars

C. Y. Tan·B. Schulz
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Abstract

We introduce a Fourier method (Fm) for the determination of best focus for telescopes with stars. Our method fits a power function, that we will derive in this paper, to a set of images taken as a function of focuser position. The best focus position is where the power is maximum. Fm was first tested with small refractor and Schmidt-Cassegrain (SCT) telescopes. After the successful small telescope tests, we then tested Fm with a 2 m Ritchey-Chr\'etien-Coud\'e (RCC). Our tests show that Fm is immune to the problems inherent in the popular half-flux diameter method.

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C. Y. Tan, B. Schulz. 2022-01-29. A Fourier method for the determination of focus for telescopes with stars. https://doi.org/10.1093/mnras%2Fstac189

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