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Astrometry.net
is a free online service for plate solving astronomical images. With
a successful solution, it creates the image
"new-image.fits". This
image is loaded into the WCS File text box, as shown above. EXcalibrator uses
"new-image.fits" to
obtain the required World Coordinate System data.
EXcalibrator assumes
that the RA and DEC reference point is at the center of the image.
This is true with PinPoint, Pixinsight and TheSkyX plate solves. The
calculated search radius covers the image from corner to corner with a
maximum of 75.0 ArcMin. With its default settings, the
Astrometry.net service may put the reference point anywhere in the
image. The worst scenario is if the reference point is at one of
the image corners. In this case the number of
potential stars for calculating the color ratios can be reduced by
75%.
Do not use a previously plate solved
image. Tests show that the RA and DEC reference point is placed at
0, 0. |
