Baader MPCC 55mm spacing

[pbkoden]

I'm hoping for some technical clarification.

We all know that the MPCC needs a spacing of 55mm. But I hear of people using T thread spacers quoting the 55mm distance, which does not make sense to me. As far as I can tell, the 55mm spacing is from the m48 thread without the stop collar. This is per the images in the Baader pdf on their website.

The included T thread adapter is actually 3mm further back than the m48 thread. When using the T thread adapter then, the spacing should be 52mm, correct? My attached image shows what I am referring to.

I plan to use my MPCC on a QSI683wsg and am trying to figure out the correct spacing. It looks like I'm working with a 52mm backspacing using the T-thread adapter.

Thanks for any help!

[Oddsocks]

I don't know if this link will work directly from a browser but it is a graphic at the Baader website for the MPCC III.

http://www.baader-planetarium.de/sektion/s17/bilder/m48-gross-03.jpg

The linking master web page is here and the relevant spacing document is contained under the M48 spacer ring for MPCC.

http://www.baader-planetarium.de/sektion/s17/s17-en.htm

It shows that the backfocus is 55 +/-1 mm from the shoulder of the T2 thread and 57.5 +/-1 mm from the shoulder of the M48 thread.

[Tinker1947]

Getting the spacing perfect is quite easy now Baader have 2 different size Vari-Lock adjusters to do the job....once you sort out the spacing, although its quite easy to try both as per your pictures...

http://www.firstlightoptics.com/adapters/baader-varilock-29-lockable-t-2-extension-tube.html

http://www.firstlightoptics.com/adapters/baader-varilock-46-lockable-t-2-extension-tube.html

[glowingturnip]

i need to get my distances sorted out too, so good information here.

Any hints on how to make the measurement accurately ?

[Tinker1947]

i need to get my distances sorted out too, so good information here.

Any hints on how to make the measurement accurately ?

The Vari-Locks have sizes marked showing the distance end to end my set-up i used the distances published for the CCD/Filter Wheel and set the gap accordingly.....

[pbkoden]

Thank you very much Oddsocks. That is exactly the info I couldn't find myself.