I was thinking about something similar to this last night! Actually I was thinking along the lines of a bifilar micrometer for measuring PA and offset, but all done in software, so perhaps its not exactly the same thing. I was thinking along the lines of say guiding on eta carinae but capturing a spectrum of the Humunculus only.
Let me ask a few questions and have a think about it, Ken...
I think an interface with PHD would be beyond me, but a stand alone overlay is something I can do.
Would you want the reticles to rotate like AlsReticle, or is it OK to keep them orthogonal to your camera?
Would you need to calibrate the reticles' relative positions in terms of real angles or would pixels do?
I'll dust off the VB.NET and have a play and see what I can come up with...
Al.
Al.