Sky Watcher x0.85 Focal Reducer Question

[FrankieValley]

Hi,

Is there an optimum distance that the Sky Watcher x0.85 focal reducer has to be placed from an imaging CCD in the same way that the Baader MPCC has to be 55mm (+/- 1mm) from it?

The reason I ask, is because I would like to use my SX OAG with my DSLR and the only way I can work out how to physically rig it up is if the OAG goes between the reducer and the DSLR.... and of course that adds distance.

Sorry, another question - when using a DSLR on my 100ED DS Pro do I really need the reducer? Obviously, it reduces the focal length, but will I see misshapen stars at the edge of field without it? I will try it out, but no harm in asking :-)

[martin_h]

Yep 55mm is the spacing, so with a DSLR and OAG your going to be to long. They are designed for direct connection to a DSLR via a M48 ring adaptor.

[FrankieValley]

Yep 55mm is the spacing, so with a DSLR and OAG your going to be to long. They are designed for direct connection to a DSLR via a M48 ring adaptor.

Thanks Martin. I was hoping that was not the answer, but suspected it would be.

I did purchase an M54 adapter thinking I could try and put the OAG on the front of the reducer, but having measured the reducer front thread with a useless plastic ruler and without my glasses on, I now realise it is larger than 54mm! Doh! Still, another handy (one day) adapter for the adapter box :-)

[Jessun]

This one might do the trick - seems to combine OAG inside the T-ring so builds only 9 or 10mm in total, it pricey though!

https://www.teleskop-express.de/shop/product_info.php?info=p1188_Off-Axis-Guider---nur-9mm-Baulaenge---Direktanschluss---Canon-EOS.html

/Jesper

[FrankieValley]

This one might do the trick - seems to combine OAG inside the T-ring so builds only 9 or 10mm in total, it pricey though!

https://www.teleskop-express.de/shop/product_info.php?info=p1188_Off-Axis-Guider---nur-9mm-Baulaenge---Direktanschluss---Canon-EOS.html

/Jesper

Thanks Jesper. I'd seen that and gawked at the price.

My finder guider is holding its own with a 765mm focal length and 10min exposures, so I think I'll stick with that and the x0.85 reducer.

I can use the OAG with my Baader MPCC on my newt and I'll also try them on the refractor at its full 900mm FL to see how the MPCC fairs there.

Thanks again :-)

[Jessun]

No worries! I think fitting this one the reducer is tricky too; they don't match straight out the box...

I use a DSLR on the SW120 and the stars do get funny at the edges and vignetting is pronounced. I think a APS chip is 'optimistic' in that scope so I've resorted to cropping haha!

/Jesper

[FrankieValley]

Whatever works :-) Thanks again.

[Sp@ce_d]

I went through this with trying to fit filters/wheel in the light train too. Seems the only chance might be to fit something between the reducer & focuser but you need adapters with the 56mm skywatcher thread. Which are thin on the ground so would be a custom job. I got a FLO adapter First Light Optics - FLO Adapter for Skywatcher Focal Reducers for using a single filter and just waiting for one of these 2 ClickLock M56 Clamp for Celeston & SkyWatcher Telescopes [baa-9a-2956256] - 60.50 : 365Astronomy: Discovery for every day! to turn up to try out. Replacing the thumbscrew fixing weakpoint on the focuser.

I also looked at this OAG Lacerta SkyFoto SkyPhoto Off-Axis Guider for Canon EOS [Lac-OffAxisEOS] - 198.00 : 365Astronomy: Discovery for every day! still expensive though!!

[FrankieValley]

...... just waiting for one of these 2 ClickLock M56 Clamp for Celeston & SkyWatcher Telescopes [baa-9a-2956256] - 60.50 : 365Astronomy: Discovery for every day! to turn up to try out.

Ah no, that's £60 you just cost me! ;-) I breezed past that in favour of an m54 adaptor and my blind measuring with a banana. Glad you pointed it back out to me as I'd forgotten about it. Saves unscrewing and disconnecting stuff as well.

Solution found. Cheers :-)