The Locus Algorithm: A novel technique for identifying optimised pointings for differential photometry

Studies of the photometric variability astronomical sources from ground-based telescopes must overcome atmospheric extinction effects. Differential photometry by reference to an ensemble stars which closely match target in terms magnitude and colour can mitigate these This Paper describes design, implementation, operation a novel algorithm – The Locus Algorithm enables optimised differential photometry. is intended identify, for given observational parameters, Field View (FoV) includes maximum number similar target. A collection objects catalogue (e.g. SDSS) filtered identify candidate determine rating each quantifies its similarity works defining locus points around star, upon FoV be centred include at edge FoV. Points Intersection (PoI) between loci are identified score PoI calculated. with highest output as optimum pointing. steps precisely defined this paper. application sample target, SDSS1237680117417115655, Sloan Digital Sky Survey described detail. has been here implemented software available online. also used generate catalogues pointings optimise Quasar studies search Exoplanets via transit method.