Selecting optimal glass combinations for atmospheric dispersion correctors

The correction of differential atmospheric dispersion is important for a broad range of astronomical observations, from high precision coronagraphy and astrometry to extremely stable fiber coupling in Doppler spectroscopy. The wide availability of adaptive optics systems, and the push to bluer wavelengths in particular, requires very highperformance designs. The choice of glasses for typical atmospheric dispersion corrector (ADC) configurations is a surprisingly challenging task, and depends on a range of parameters, in particular the wavelength range, with considerations on the level of dispersion correction as well as transmission and mechanical parameters. Finding the optimal glass combination with optical raytracing programs is time consuming, and it is hard to verify the solution is optimal. We describe a numerical method that uses Python to evaluate all possible unique combinations of two glasses from an input catalogue. This enables easy identification of potentially good candidate pairs for further, detailed investigation.