Calculate radial velocities of the GBT

UT date UT time Right Ascension Declination V-Helio V_LSRK
"?" km/sec "?" km/sec

This gives the velocity in the direction (RA,Dec) from the point of view of the GBT.
Positive means it is receding from us (redshift); negative, it is approaching (blueshift).

V-Helio is the velocity due to the rotation of the Earth and the motion of the Earth in its orbit around the Sun.

V-LSRK is the velocity towards the local standard of rest (LSR), in addtion to the motions of the Earth.

Measurements within our galaxy are usually referred to the LSR.
Measurements of extragalactic objects are usually referred to the Sun (heliocentric or barycentric).

(These calculations apply just as well to the Green Bank 20-meter telescope.)