Precession, Nutation, Annual Aberration, Refraction Calculator
Right Ascension =
Declination =
Sidereal time =
Latitude =
Coordinate year =
Calculate for date =



Right Ascension Declination
Precession = 00:00:00.000 00°00'00.000"
Nutation = 00:00:00.000 00°00'00.000"
Annual aberration = 00:00:00.000 00°00'00.000"
subtotal = 00:00:00.000 00°00'00.000"
Refraction = 00:00:00.000 00°00'00.000"

Notes:

Precession depends on the coordinate year and the desired target date. Nutation and annual aberration depend on the target date. Refraction depends upon elevation which depends on the hour angle (sidereal time - Right Ascension), Declination and latitude. Precession dominates the coordinate corrections with refraction when at low elevations. At a minimum, precession should be incorporated into coordinates for use at the telescope along with refraction when pointed near the horizon. Proper motion is ignored.

Right Ascension hours can be entered in a variety of formats. For example, '05h 12m 20.2sec', or '5 12 20.2' or '5:12:20.2' or simply ,'5' for 5 hrs. Decimals can be used anywhere, e.g., '5.5h' is 5h 30m. Any reasonable spelling or shorthand of hours, minutes and seconds can be used. Radians can also be used, e.g., 1.2 radians or 1.2rad or 1.2r.
Declination degrees can be entered in a variety of formats. For example, '+41°16'10.0"' or '41d 16m 10s' or '41 16 10' or '41:16:10' or simply '4' for 4 degrees. Decimals can be used anywhere, e.g., '5.5' is 5d 30m. Any reasonable spelling or shorthand of degrees, minutes and seconds can be used. Radians can also be used, e.g., 1.2 radians or 1.2rad or 1.2r.
Ditto for Sidereal time and latitude.

Mel Bartels