DONUTS: A science frame autoguiding algorithm with sub-pixel precision, capable of guiding on defocused stars

TL;DR

DONUTS is an autoguiding algorithm capable of high-precision, sub-pixel corrections on defocused stars, enhancing high-cadence photometry by maintaining accurate telescope pointing.

Contribution

It introduces a novel autoguiding algorithm that works effectively on under-sampled and defocused stellar images, improving precision in high-cadence photometric observations.

Findings

Effective on-sky performance demonstrated

Works with heavily defocused stars

Suitable for high-precision photometry

Abstract

We present the DONUTS autoguiding algorithm, designed to fix stellar positions at the sub-pixel level for high-cadence time-series photometry, which is also capable of autoguiding on defocused stars. DONUTS was designed to calculate guide corrections from a series of science images and re-centre telescope pointing between each exposure. The algorithm has the unique ability of calculating guide corrections from under-sampled to heavily defocused point spread functions. We present the case for why such an algorithm is important for high precision photometry and give our results from off and on-sky testing. We discuss the limitations of DONUTS and the facilities where it soon will be deployed.