OAG Input

[Stephen]

Following on from blinkys thread about which guide camera to use, I wonder if anyone can give me any input on the following combination:

80ED reduced (or something with similar aperture at about f5.6)

TS OAG (don't think it matters which one)

DSIc (Mk I or QHY5 which I believe to be "less" sensitive than the DSIc)

Has anyone used this variation of setup with any success? It's not so much the spacing and distances, it's actually being able to resolve a guide star.

I'm reasonably confident my 8" f4 will be OK, it's just the smaller scope I am concerned about ...

Thanks in advance

[Merlin66]

I see you have the WO72 and a DSI-C in your box.

Put them together and try it.

If you can find a guide star (and I'm 110% sure you will) then you get the same performance from a OAG.

[rfdesigner]

You could have trouble with the F4.

Work out all the distances and establish just how far away from the guide prism your guide camera is going to be, if you've got a lot of back focus from your OAG to the imaging camera then your guide camera will need to be a long way back and a small pick of prism will vignet the guide signal, the question is, how much.

My setup vignets even at the centre of the guider, but as it's only about 5% loss at the centre it still performs very well.

Derek

[ollypenrice]

On a short FL scope I wouldn't go near an OAG myself. What a palaver and for what gain? We use an OAG on Yves' big scope because you need to do so but on anything up to a metre it is soooooo much easier to use a guidescope. Or so it seems to me. My only ever issue with diff flexure was with the OAG...

Olly