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9.9.2 CCD Scale

tastrom directly outputs the CCD scales in the x and y direction, sx' and sy', in the image.ast file, with 4 decimal places. A manual calculation using the found values of $\alpha$ and $\beta$ and equation ([*]) gives the same result. The scales are shown in Figure [*]. There seems to be a small difference between the x scale and the y scale. This is small enough to be ignored.

The horizontal dotted-dashed line shows the adopted value of the CCD scale of 0.5073 ''/pixel. This is actually not a mean of all the data, but only of 6 images on which astrometry was done at an earlier point. However, this value is very representative for all the data, as the figure shows.

  \begin{figure}% latex2html id marker 22215\makebox[\textwidth]{
The horizontal dotted-dashed line is at 0.5073 $''$ /pixel.

Properties of E and S0 Galaxies in the Clusters HydraI and Coma
Master's Thesis, University of Copenhagen, July 1997

Bo Milvang-Jensen (