OAG on an ED80???

[Pint Of Stellar]

Can anybody advise please if it's possible to image with a dslr if an ED80, fitted with the FF/FR, is off axis guided? If so, are there any particular makes to go for/avoid?

[dmahon]

The short answer: Yes, of course.

The longer answer: It depends on your focal reducer and what the spacing requirements are. If the requirements are 55/56mm, then there is only enough room for the camera and a T-ring, not the OAG (however I think there is one very short one that can attach directly to the camera to get around this - probably from Telescop Express)

[rkc]

I think the FF/FR is designed for a back-focus of 55mm, leaving no room to get an OAG between it and the DSLR. At least, that's my understanding, but I'd be very interested in any alternative answers as I'd quite like to try the same setup myself.

[Pint Of Stellar]

So - according to this wiki page

http://en.wikipedia.org/wiki/Flange_focal_distance

it looks like the APS-C allows for 44mm of space from the chip to the front of the mount ring - does this then mean that as long as the OAG and T-Ring combo is 12mm we're OK?

[Pint Of Stellar]

And now I've read this topic and am still none the wiser - I get a sense that it's possible but not quite sure with this FLO OAG...

http://stargazerslounge.com/topic/178892-new-off-axis-guider/

[rkc]

I happened across this http://www.365astronomy.com/lacerta-offaxis-guider-for-canon-eos-m48-thread-p-2217.html when looking for something else entirely - it looks like it might work (should fasten directly to the back of the FF/FR). Anyone tried it?

[lensman57]

I think the FF/FR is designed for a back-focus of 55mm, leaving no room to get an OAG between it and the DSLR. At least, that's my understanding, but I'd be very interested in any alternative answers as I'd quite like to try the same setup myself.

You are correct, most FF/FRs including the ones from SW are desigened for 55~57mm of back focus, that is the exact distance from the flange to the sensor of Canon cameras with Nikon being slightly longer, an OAG will not fit in. There are some FF/FRs designed to work with filter wheels but these need to be sourced from suppliers separately , TS have these but wether they match the ED80 is another matter.  As for the OP the question is why use an OAG with a short FL scope, OAGs are primarly for long FL SCTs and he will be better advised to use a 50mm guider. Getting the OAG parfocal with the scope and the camera is a rigth royal pain that no one needs.

A.G

[ollypenrice]

You are correct, most FF/FRs including the ones from SW are desigened for 55~57mm of back focus, that is the exact distance from the flange to the sensor of Canon cameras with Nikon being slightly longer, an OAG will not fit in. There are some FF/FRs designed to work with filter wheels but these need to be sourced from suppliers separately , TS have these but wether they match the ED80 is another matter.  As for the OP the question is why use an OAG with a short FL scope, OAGs are primarly for long FL SCTs and he will be better advised to use a 50mm guider. Getting the OAG parfocal with the scope and the camera is a rigth royal pain that no one needs.

A.G

My thinking entirely. You'll have a far greater choice of guide stars in a separate scope. For me OAGs are a necessary pest when working with a big reflector. Part of the pleasure of refractor imaging is not bothering with them!

Olly