Astrometric Position Calculator

Use this page to compute accurate equatorial coordinates (Right Ascension and Declination) for an object in your image --- an asteroid or comet, for example. If you have a question about what an entry box is asking for, or the meaning of a result box, click on the nearby "?". A set of example entries is given; note their format. Clicking on the "Calculate" button will compute "plate constants" for the image and the RA and Dec for the object using a standard astrometric calculation procedure.
Enter approximate RA Dec of center of image (hh mm ss.s... ±dd mm ss.s...): ?

Enter number of stars to use in calculating the plate constants (at least 4, no more than 10): ?

Enter for each star its RA Dec, and the x y pixel coordinates of its image centroid (?)
(RA Dec in the format hh mm ss.s... ±dd mm ss.s...; x y in the format xxx.xxx... yyy.yyy...):
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:
RA Dec: x y:

Enter x y pixel coordinates of the centroid of object of unknown RA Dec:
?



Resulting plate constants(?):
a = b = c =
d = e = f =

Resulting RMS residual in RA (seconds) and Dec (arcseconds): (?)
Resulting RMS residual in arcseconds: (?)

Resulting RA Dec of object: (?)
This astrometric position calculator is based on a BASIC program written by Jordan D. Marche and explained by him in the July 1990 issue of Sky & Telescope, page 71.
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