EdgeHD 11", 0.7x Focal Reducer and SBIG STXL 11002 Image train.

[stefang (Stefan)]

Hi guys,
I am in the process of pulling together the imaging train for an Edge HD 11" with .7 Focal Reducer, STXL 11002 & Self Guiding Filter Wheel setup.

I understand I have 146mm of back focus with or without the focal reducer according the Celestron whitepapers and documentation.

I also understand that its better to be slightly inside of focus than outside of focus.

Connecting from the rear of the 0.7 reducer to the 3" accessory faceplate is the piece of the puzzle I am uncertain about.

According to Diffraction Limited, back focus distance for the STXL, Filter Wheel etc is 2.347"(59.6138mm) with an additional .672' (17.0688mm) for the 3" accessory ring on the camera.

My current understanding is that I need a precise parts adapter between the Reducer and the 3" accessory ring on the STXL as I need to make up 69.32mm in extension tubes & any adapter required.

Should I be considering just 3" extension tubes from the .7 focal reducer threads to the STXL 3" accessory plate? Do i need a seperate custom adapter to join the dots?

The Focal Reducer thread is M80 - The STXL 3" accessory plate Thread is M72 (72.39mm).

I am looking to stand on the shoulders of giants on this one, before I blow a bunch of cash on adapters at precise Parts etc that are not right.

Any assistance greatly appreciated for anyone that may have a similar setup or can point me in the right direction.

Clear skies.
stefang

[Camelopardalis (Dunk)]

Stefan, have a look at the measurements again, I think you're quoting inches and not mm

[stefang (Stefan)]

Doh! updated with mm conversions. Damn those imperial yanks.

[Camelopardalis (Dunk)]

Lucky the multi-measurement Pom caught it

The optical diameter of the reducer is only 52mm camera side IIRC so 3" is probably overkill, but then 2" would be too narrow for your sensor.

FWIW, the only time I've tried DSO imaging with mine, the seeing has been sufficiently poor to destroy any resolution advantage of the focal length. If you consistently get better seeing, then let me know how you get on!

[stefang (Stefan)]

250 bucks for the adapter and $50 USD for postage
I wish i could send my money to someone in Australia to make these adapters.

Any professional machinists on IIS?
stefan