An Optical Distortion Solution for the Keck I OSIRIS Imager

Freeman, Matthew S. R. and Lu, Jessica R. and Lyke, Jim and Gautam, Abhimat and Kupke, Renate and Ghez, Andrea and Sakai, Shoko and Anderson, Jay and Bellini, Andrea (2023) An Optical Distortion Solution for the Keck I OSIRIS Imager. The Astronomical Journal, 166 (3). p. 125. ISSN 0004-6256

[thumbnail of Freeman_2023_AJ_166_125.pdf] Text
Freeman_2023_AJ_166_125.pdf - Published Version

Download (4MB)

Abstract

The astrometric precision and accuracy of an imaging camera is often limited by geometric optical distortions. These must be calibrated and removed to measure precise proper motions, orbits, and gravitationally lensed positions of interesting astronomical objects. Here, we derive a distortion solution for the OSIRIS Imager fed by the Keck I adaptive optics system at the W. M. Keck Observatory. The distortion solution was derived from images of the dense globular clusters M15 and M92 taken with OSIRIS in 2020 and 2021. The set of 403 starlists, each containing ∼1000 stars, were compared to reference Hubble catalogs to measure the distortion-induced positional differences. OSIRIS was opened and optically realigned in 2020 November and the distortion solutions before and after the opening show slight differences at the ∼20 mas level. We find that the OSIRIS distortion closely matches the designed optical model: large, reaching 20 pixels at the corners, but mostly low order, with the majority of the distortion in the 2nd-order mode. After applying the new distortion correction, we find a median residual of [x, y] = [0.052, 0.056] pixels ([0.51, 0.56] mas) for the 2020 solution, and [x, y] = [0.081, 0.071] pixels ([0.80, 0.71] mas) for the 2021 solution. Comparison between NIRC2 images and OSIRIS images of the Galactic center show that the mean astrometric difference between the two instruments reduces from 10.7 standard deviations to 1.7 standard deviations when the OSIRIS distortion solution is applied. The distortion model is included in the Keck AO Imaging data-reduction pipeline and is available for use on OSIRIS data.

Item Type: Article
Subjects: Science Global Plos > Physics and Astronomy
Depositing User: Unnamed user with email support@science.globalplos.com
Date Deposited: 17 Nov 2023 04:19
Last Modified: 17 Nov 2023 04:19
URI: http://ebooks.manu2sent.com/id/eprint/2092

Actions (login required)

View Item
View Item