A Fourier method for the determination of focus for telescopes with stars
arXiv:2201.12466 · doi:10.1093/mnras/stac189
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-Chrétien-Coudé (RCC). Our tests show that Fm is immune to the problems inherent in the popular half-flux diameter method.
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) Published by Oxford University Press on behalf of the Royal Astronomical Society