urn:nasa:pds:context:instrument:mcdonald.harlanjsmith_2m7.p45a_phot 1.3 1.25.0.0 Product_Context urn:nasa:pds:context:instrument:mcdonald.smith2m7.p45a_phot 2026-07-07 1.3 Removed duplicate Internal_Reference entries from Reference_List. 2025-12-24 1.2 Updated schema version. Adding missing "facility" references. Adding missing "telescope" references. Updated CTLI instrument types. 2025-01-02 1.1 Updated schema version. Adding missing "telescope" references. 2021-12-07 1.0 per RMS, deprecated mcdonald.smith2m7 in favor of mcdonald.harlanjsmith_2m7 urn:nasa:pds:context:telescope:mcdonald.struve2m1 instrument_to_telescope urn:nasa:pds:context:telescope:mcdonald.harlanjsmith_2m7 instrument_to_telescope urn:nasa:pds:context:telescope:mcdonald.0m91 instrument_to_telescope urn:nasa:pds:context:facility:observatory.mcdonald instrument_to_facility Binzel, R.P. and J.D. Mulholland, Photometry of Pluto during the 1982 opposition, Astron. J. 88, 222-225, 1983. McDonald P45a Two-Channel Photometer Photometer The McDonald P45a Two-Channel Photometer is a sensitive instrument designed for measuring light intensity from astronomical sources in two different wavelength bands. It is particularly used for photometric observations, enabling detailed study of variable stars and other celestial phenomena.