Update default GSC to 2.4.2
Update default Guide Star Catalog to 2.4.2, remove support for Python 3.5 and add Python 3.8, and add direct FGS magnitude to count rate and count rate to FGS magnitude functions.
Update default Guide Star Catalog to 2.4.2, remove support for Python 3.5 and add Python 3.8, and add direct FGS magnitude to count rate and count rate to FGS magnitude functions.