Formula used to calculate the image scale from focal length is not right

[saikewei]

In stellarsolver/internalextractorsolver.cpp, line 1118,1119

appu = rad2arcsec(atan(36. / (2. * scalelo))) / (double)m_Statistics.width;
appl = rad2arcsec(atan(36. / (2. * scalehi))) / (double)m_Statistics.width;

I think the formula used to calculate the image scale from focal length is not right. The fix is to multiply the result by 2.
For example, the width of the image shot by my camera is about 7k pixels. When using 200mm lens, the correct arcsec/pixel is about 5.3.

This issue makes the solver unable to solve when the user uses scale in focalmm mode.

[rlancaste]

You might be right about this. focalmm is a setting I generally don't use and I don't know anyone who does use it regularly. I will try to test your fix to see if this works.