Till date, I have only done this "in my head", using relative orientations.

Recently, I coded a feature for KStars (http://edu.kde.org/kstars) planetarium to render an "Eyepiece View", as is present in many other software (not that I've used them, but anecdotal / internet reading / heresay).

The most interesting thing (which I don't know if it is common in other software etc.) is automatic adjustment of the orientation of eyepiece view for a (big) dob. I don't know if this is already widely known information or is too obvious (it was not for me), but the formula seems to be simple:

1. Rotate the DSS image for the location date and time such that the altitude points up. This accounts for the orientation of the POSS image in the sky.
2. Then invert the image (i.e. rotate by 180 degrees). This accounts for the inversion by the telescope.
3. Then rotate clockwise by an amount equal to the altitude of the object. This accounts for the fact that the reference frame of alt/az that is natural to the dob is rotated clockwise by an amount equal to altitude of the scope from the ground reference frame (vertical/horizontal).

Putting these three together seems to work very well in generating the exact orientation for the POSS image that matches the eyepiece view from my dob (which is Obsession, has a focuser that is horizontal; not at an angle like in the smaller dobs, and I configure it so the focuser is on the left of the dob when looking up the OTA).

I've noticed that a lot of us have been manually rotating the POSS to match field-of-view. I wonder if this idea is universal / if there is some fundamental problem with automatically predicting the orientation, although this seems to work very well for my scope.

I wonder if there is a way to extend other planetarium software to incorporate this feature.

Any information / discussion on this subject will be appreciated.

Clear Skies

Regards
Akarsh