[Enchilada]

Following up on the previous post, I was surprised that no one commented on using the Java software ALADIN. Most seem to think this software is very complex, but is open-ended enough to allow very useful physical data on deep-sky objects or positions of double stars. This 778k to 1.7Mb software can calibrate known positions of stars from your jpg, png or gif images, and can even correct for field image orientation and projections. You can also create and use many basic and advanced filters or write your own Plugins.
Coupled with the SIMBAD Database, there is little one can do that someone only dreamed at a few years ago! Ain't technology just grand!
I have created and attached a slightly useful pdf file here to do basic calibrations, so you can measure doubles etc. - as well as answering the interesting position angle problem expressed here. (Compared to the mathematical pdf in my previous post - well it is not so mind-numbing.) I have particularly dumbed down the text, mainly not to put people off - but also to highlight the real power of ALADIN for those who are not aware of its existence. Interested amateurs can explore this software in far more detail to cater more for their personal interests. Best of all it is FREE and is not operating system dependent!