In order to recorde PE, we need to know the RA direction and scale in the camera coordinate system (aka pixels).
To perform this, pe recorder with stop the mount, then monitor the star movement in the camera while the mount is stopped.
We know that the star will move towards West, and that the speed will be the earth rotation speed.
So we can mesure a drift speed in pixels/second, and as we know that this drift speed is roughly 15.04 arcsec/sec (sidereal rate), we can
relate pixel size and arc seconds. In this calculation, the declination of star is taken into account : the apparent speed is
sidereal rate * cos(declination).

While the mount is stopped, pe recorder will record a list of times and star position. A linear regression is performed. As the points are
supposed to be aligned, the calibration will fail is correlation of the linear regression is too low.


EQMOD specific

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