This is my copy of the US Naval Observatory's NOVAS-C software (https://aa.usno.navy.mil/software/novasc_intro) with a couple bug fixes applied. I've also enhanced it with the ability to open many more versions of the JPL ephemerides. Please give the USNO proper credit if you use this software.
When NOVAS C 3.1 computes Greenwich Mean Sidereal Time (GMST; gst_type = 0) using the method based on the Celestial Intermediate Origin (CIO; method = 0), the units for the equation of the equinox are calculated incorrectly.
In sidereal_time, the line
ha_eq -= (eqeq / 240.0);
should read
ha_eq -= (eqeq / 3600.0);
since the eqeq variable has been previously converted to arcseconds instead of seconds in time.
When NOVAS C 3.1 computes Greenwich Mean Sidereal Time (GMST; gst_type = 0) using the method based on the Celestial Intermediate Origin (CIO; method = 0), the units for the equation of the equinox are calculated incorrectly.
In sidereal_time, the line
ha_eq -= (eqeq / 240.0);should read
ha_eq -= (eqeq / 3600.0);since the eqeq variable has been previously converted to arcseconds instead of seconds in time.