Baader MPCC question

[pook]

Can I ask what the stopper collar is actually for?

As it says above, remove for Dobsonian use, and install it for photo-newtonian use.

I'm confused... what's the difference? Surely a Dob is just a newt like any other... just the mount that's different.

Why do I need to remove the collar for Dob use?

[david o]

Could be that by Photo-Newton they mean astrograph ?

That possibly with astrographs the coma corrector needs to be further out ?

Flumoxed

[blinky]

I have been wondering exactly the same thing!

[Macavity]

Doesn't the FULL document help any?

http://www.baader-planetarium.com/pdf/mpcc_e.pdf

[pook]

Not really. That's where I got the picture from. It just says use the stopper ring on a newt, but not on a Dob. LOL. I could put my scope on a Dob mount, and it would be a Dob... back on my EQ and it's a newt.

I fail to see the difference.

[Uranium235]

The collar is for fine-tuning the position of the MPCC to make it exactly 55mm from the CCD or CMOS chip, well... thats what I use it for.

[Macavity]

So presumably the camera sits in approximately the SAME position (relative to the OTA) with the MPCC (55mm) inside the focal plane? Actually, I'm trying to decide on 2" extensions for occasional *visual* use, but the general idea should hold? I sense the MPCC has little real optical strength, being more of a "corrector", right?

[David010167]

If you remove the stopper coller the whole unit can then fit inside a 2" focusing tube - this is then reliant on the item to which you have attached the MPCC to control the correct distances etc. With the collar the MPCC can only sit in/on a 2" focuser.

If you look at the PDF linked by Chris above you will see what I mean in some of the photos.

regards

David