Quote:
Originally Posted by [1ponders]
Mike, after rereading your thread title I realized I didn't answer your question about how accurately to align your 2 scopes.
As I understand it, if you were absolutely perfectly polar aligned then it shouldn't matter how much the two scopes are misaligned. In practice though it does.  The further you are from exact polar alignment and the further you are from guiding on the same point that is central to your image the greater effect it will have on your image, normally in some form of field rotation. Length of exposure has an effect as well on the outcome.
That's how I had it explained to me. Having said all that I can't say I've noticed many problems, but then my polar alignment process is very accurate (arcsec accuracy) and I stick to fairly short exposures, rarely longer than 10 min. I also use guiderings so its rare that I need to guide at a distance from the point I'm imaging.
Don't know if that's helped or not  |
Thanks for the input, Paul.
As I'm looking at an "instantaneous" viewing divergence, I don't think polar alignment will have much to do with it, it's just "two scopes looking in different directions".
Just for everyone's info, (I know you're all enthralled), I went out and took a look at the ADM plate under the ED80, and it has two threaded holes where I can put some jacking screws a la Al's suggestion, so will try that as soon as the clouds run away.
I was just ordering a WO 4 FF so threw in a set of 100mm guide rings as well, so hopefully the whole RHS can get tied down well.
My concept is to have a permanent RHS setup of the WO 80 triplet with DSI II guidescope on top, and the LHS swapping between F5 newt + MPCC and various combinations of C8 FR/Hyperstar.
Somewhere in all of that tinkering, I may even find time to take a happy snap of M42