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Off Axis Guiding Choice...?


MG1
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I was wondering if anyone has any experience of OAG with DSLR's?

I've been considering adding the SX-OAG (Starlight Xpress Accessories - Starlight Xpress Off-Axis Guide Head) to my SX-filterwheel, then using my lodestar with that and freeing up the WO66 for a bit of double splitting whilst I'm imaging.

:p visual :p I know....;)

Anyway, I think I've worked out that for it all to work with the WO/TMB Field flattener I'm a little limited on the back focus.

If I go with the SX-OAG then I will probably need to use one of these: Adapter: T2 Innengewinde auf EOS Bajonett - 0mm Baulänge

a very low profile t-ring adapter.

I'll then also need around a 7-8mm t-ring spacer to get the correct chip-lens distance for the FF and to be able to connect the camera to the filterwheel (otherwise if fouls the wheel body)

The other option is to go for the TS 9mm OAG: Off Axis Guider - nur 9mm Baulänge - T2 Anschluss - für CCD.

but this doesn't seem as solid and I would also need a t-thread to c-mount adaptor which again is likely to upset the focus of the lodestar. (btw, if looking for a c mount adapter don't make the mistake I did and google c-ring....:) something quite different!)

The final choice as far as I can see is this: Lacerta Off-Axis Guider for Canon EOS M48 Thread [Lac-OAGhu48] - £226.73 : 365Astronomy: Discovery for every day!

It looks solid but again has the t-thread issue and would need to be positioned behind the filter wheel. This seems a little daft in that I'm loosing light to the guide star if I'm shooting through filters.

Also it will need replacing when i finally am tempted into the even darker world of dedicated CCD cams...:)

Does OAG increase vignetting at all?

So, any suggestions? I saw quite a few of the SX setups at SGL and they doooo look solid.

Or should I just stick to the piggyback WO-66 and add more weight?

ANy thoughts, experience or comments welcomed.

Cheers guys

Michael

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If you don't use a Newtonian you don't have to use those ultra short ones. TS has (will have) "TS Flip" - 35mm flip mirrir & oag in one. Standard semi-sized OAG would be Brightstar Astro Off Axis Guider (branded by Orion also). There is also Celestron Radial Guider for long backfocus refractors (or SCT), or shorter T-threaded version as Baader RCC Off Axis Guider. They shouldn't increase vignetting. For example Radial Guider was designed long ago for analog astrophotography - so it had to be compatible with something like a "full-frame" film. That's more than APS-C in DSLR.

BTW. U.K. Astronomy Buy & Sell

Edited by riklaunim
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Cheers, but I need to get as close to 113mm as possible between the lens of the field flattener and the camera chip. From the flattener there is the following at the moment

6 mm - to edge of FF

12.5 mm - flattener to SCT adaptor

29 mm - SX filter wheel (Inc adaptors)

10.5mm - t-thread spacer

11mm - t-thread to EOS adaptor

44mm - standard chip to flange for EOS

So therefore the larger OAGs just won't fit in.

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