Speaker
Description
Accurate photometric calibration of astronomical photographic plates remains a fundamental challenge in astronomy due to the mismatch of spectral sensitivities of photographic plates and pass bands of modern calibration catalogs.
We intend to derive consistent natural magnitudes for celestial sources within the intrinsic photometric systems of astronomical photographic plates by using Gaia Data Release 3 (DR3) blue-photometer (BP) and red-photometer (RP) low-resolution spectral data, and to show its superiority over former methods.
We compiled spectral characteristic data for emulsions and filters applied in photometric observations using glass plates. The collected color sensitivities, modified by atmospheric reddening depending on the air mass, were then used to compute accurate natural magnitudes and fluxes of objects in the photographic plates through synthetic photometry. These natural magnitudes are then compared with results from the color-term method used to compile the data in existing photoplate archives.
We were able to reveal systematic errors of the existing data in the range of $\pm 0.3$ mag and higher. In addition, the presented method allows for an accommodation of stars with similar color index but of different luminosity classes as well as an effective correction of atmospheric reddening at higher air masses (approximately 0.2 mag). First results of the calibration of a photoplate using the new natural magnitudes are presented.
