A simple concept for atmospheric dispersion correctors on-sky commissioning tests

Alexandre Cabral; Bachar Wehbé

doi:10.1117/12.2562463

13 December 2020 A simple concept for atmospheric dispersion correctors on-sky commissioning tests

Alexandre Cabral, Bachar Wehbé

Proceedings Volume 11447, Ground-based and Airborne Instrumentation for Astronomy VIII; 114475W (2020) https://doi.org/10.1117/12.2562463
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Conference Poster

Abstract

Differential atmospheric dispersion, due to the wavelength-dependent index of refraction of the atmosphere, will affect ground based observations. In order to correct this effect, the usage of an Atmospheric Dispersion Corrector (ADC) is fundamental. Insufficient, or wrong correction of the atmospheric dispersion, will produce a spectrally elongated shape instead of a circular white one for the observed target. The commissioning tests of ADCs with on-sky observations are not an easy task. In fact, the residual dispersion is expected to be of a few tens of milliarcsec, where the object for a seeing limited telescope is almost 1 arcsec. A procedure was developed, based on ellipse fitting of several cuts from the guiding camera images. The characterization of the data allows the validation of the ADCs alignment by determining the dispersion direction and by minimizing the ellipticity. The procedure was tested on ESPRESSO using the guiding camera images, and was able to correct a small error of a few degrees in the ADC prism alignment that was not possible to infer by other means.

Citation Download Citation

Alexandre Cabral and Bachar Wehbé "A simple concept for atmospheric dispersion correctors on-sky commissioning tests", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114475W (13 December 2020); https://doi.org/10.1117/12.2562463

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