“Investigação da influência de efeitos instrumentais e atmosféricos na astrometria de imagens CCD”

Abstract

The greatest advancement in modern optical Astrometry has been the Gaia catalog. It solved long-standing challenges in the construction of reference catalogs with precise positions, free from the accumulation of systematic errors. This allows medium and small telescopes to be used more efficiently for determining the positions of small Solar System bodies. These positions require constant monitoring, and observations are mostly made using this type of telescope. Obtaining precise positions for these astronomical objects enables more accurate ephemerides, which in turn improves the prediction of events related to their study, such as stellar occultations.

The solution provided by the reference catalog for positions places responsibility on astrometric reduction. Improving this aspect involves a better understanding of instrumental and atmospheric effects that influence the determination of celestial object positions. To this end, a good alternative is the use of optical simulations of astronomical instrumentation to reproduce, manipulate, and measure these effects.

In this work, we used the KrakenOS optical simulator to reproduce two instruments widely used for observing and obtaining position measurements of small Solar System bodies. These are two telescopes from the Pico dos Dias Observatory (OPD/LNA): the 1.6-m Perkin-Elmer (PE1.6-m) and the 0.6-m Boller-Chivens (BC0.6-m). The goal is to create a tool that generates an astronomical image entirely based on simulation, taking into account the optics of the instruments. The simulated astronomical image should include all the characteristics of a real astronomical image, including the reproduction of the flux from astronomical sources, atmospheric effects, and counts related to the noise present in the image. Additionally, the text addresses the importance of considering effects such as misalignments of instrument components and atmospheric refraction, which can affect the positions of stars in the images. The developed tool aims to improve the accuracy of astrometric reductions by better characterizing optical systems and monitoring their behavior over time.

Finally, we present the results of this tool, comparing them with a real astronomical image. The sources reproduced in the image have a flux based on a Gaussian PSF and a visual distribution in the CCD (Charge-coupled device) field equivalent to that of the real image. The effects of atmospheric turbulence, based on Kolmogorov turbulence models, were also reproduced, although this aspect requires further refinement.