Resulting RMS residual in arcseconds
This is the uncertainty (or error), in any direction on the sky,
in the determination of the RA and Dec of the object (e.g., asteroid).
It is expressed in arcseconds. In other words, the object is most
probably within a circle of this radius centered on the RA and Dec
determined for the object.
If this value is large (10's of arcseconds, or more), it is likely you
made a mistake in entering your star data (sky coordinates, or x,y
pixel coordinates), or you made a mistake in your identification of
stars in the image.
Technically, this value is the root-mean-squared (RMS) difference
between the actual RA, Dec position of the stars used to determine the
x,y-to-RA,Dec transformation and the RA, Dec coordinates determined
for these stars by the transformation.
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