Baader MPCC, DSLR, Newtonian help!

[yelsac]

Hi

I’m using a Canon 1100d with a t-ring to attach direct to a normal stock focuser on a skywatcher 150p (Black & White) & to an old blue style 250px again with the stock focuser.

I want to get a Coma Corrector, I've been looking at a Baader MPCC but need to find out if there will be any focusing issues if I add the MPCC to the setup?

I've read alot of posts with different opinons, so I really wanted to ask if anyone has tried this setup, has it worked or do you have to get another adapter etc etc?

thanks for looking

Yelsac

[Tinker1947]

I used a Baader CC with a Canon 1100D/600D into a  250P-DS the spacing is already set, the CC slides into the focus tube, you may have to check you have enough inward travel if your scope is not a P-DS type....

[Apharov]

As said by Tinker1947, the MPCC will go into the 2" focuser. The resulting train of pieces will be thus: DSLR - EOS->T2 - MPCC - focuser. On my 200PDS and 130PDS there's not a huge amount of inward focuser range remaining, so it might be a critical problem with P/PX.

The possible focus range problem cannot be solved by additional adapters, you'd need to modify the scope to move the focus plane further outside the tube.

[steppenwolf]

If your blue tube 250P has the original rack and pinion focuser then you will not be able to achieve focus with the standard adaptors - the 2" adaptor supplied adds far too much extension. I wanted to use a Baader MPCC with my blue tube 250P and designed my own adaptor that inserted into the non-standard 'throat' and neatly placed the MPCC deep into the focus tube. Here are a couple of photos:-

My original design submitted to the machinist

The machined adaptor

The MPCC attached to the adaptor

[yelsac]

If your blue tube 250P has the original rack and pinion focuser then you will not be able to achieve focus with the standard adaptors - the 2" adaptor supplied adds far too much extension. I wanted to use a Baader MPCC with my blue tube 250P and designed my own adaptor that inserted into the non-standard 'throat' and neatly placed the MPCC deep into the focus tube. Here are a couple of photos:-

My original design submitted to the machinist

The machined adaptor

The MPCC attached to the adaptor

Thanks for you reply

Forgive my ignorance So are you saying that basically the adapter you designed means the MPCC goes deeper into the focuser than without thus enabling you to gain focus?

this is what I was hoping to do as per page2

http://www.baader-planetarium.uk.com/en/pdf/Baader_MPCC_Instructions.pdf

[steppenwolf]

Forgive my ignorance So are you saying that basically the adapter you designed means the MPCC goes deeper into the focuser than without thus enabling you to gain focus?

Yes, that's exactly right!

[yelsac]

Yes, that's exactly right!

Thanks for clarifying that

Have a look at the picture below, I seem to have quite a bit of inward travel still available on my focuser with my DSLR in sharp focus its about 17mm -18mm

Is that the same as you've got?

[steppenwolf]

I had slightly less than you if the attached photo was at focus (and I'm sure it was!). However, the issue with the MPCC is that although it has a male 'T' thread to fit your Canon 'T' adaptor, the female thread at the other end is 48mm (to accept a standard 2" filter) so it won't fit the Sky-Watcher focuser 'T' adaptor that you are currently using, rather, it is designed to fit a 2" eyepiece holder. Unfortunately, the 'throat' of the focus tube is not 2" in diameter so SW supply a 2" eyepiece adaptor BUT this adds 36mm of extension!! Taking off your 18mm of inwards travel means that you would be approx 18mm short of inwards travel to achieve focus if you used the SW 2" adaptor. To resolve this issue, you have to get the MPCC inside the actual focus tube hence my cunning design which works. However, please be aware that this was designed for my CCD camera which has a backfocus of 17.5mm so if you went down this route you would need to modify my design to suit a DSLR camera with its 55mm backfocus requirement.

What I would suggest you do is use the SW supplied 2" adaptor but have it machined down to just 15mm depth and then drill and tap two holes in the reduced length collar to accept the original two locking bolts. This would give you a 2" eyepiece adaptor for the MPCC to locate in so it would be inside the focuser throat and you would retain the 55mm spacing required by the MPCC, all at minimal cost. The MPCC conveniently imparts approx 10mm of additional inwards focus travel as a bonus. If you use the existing adaptor for 2" eyepieces, please bear in mind that your eyepieces may not achieve sufficient outwards movement to achieve focus once you have cut it down to suit the MPCC!!!

[fwm891]

You can always tweak the primary mirror 'up' the tube a few mm's with the collimation bolts to gain a little more focuser travel

[yelsac]

You can always tweak the primary mirror 'up' the tube a few mm's with the collimation bolts to gain a little more focuser travel

Thats a good idea I never thought of that.

cheers