Re: AP1100AE needs exorcism (DEC turned all the way around like Linda Blair)
Hi Linwood,toggle quoted messageShow quoted text
The problem did have to do with the refraction option, but it was just the lack of initialization of the site's latitude, which is contained in the missing PNT file. If you unchecked the refraction option in APCC then the problem would go away.
In case you are interested, the actual problem was not the refraction calculation itself, but that APCC would pre-calculate the sine and cosine of latitude before using them so that it would not have to recalculate the same value all of the time. However, since the PNT file was missing, the latitude's sine and cosine values were never pre-calculated. The problem was that the cosine of latitude=0 is 1, but since it was never initialized, it remained at the default value of 0, causing large Alt/Az to HA/Dec computation errors.