My images taken with my Canon 5D on my 12 inch F/5 Newt. shows very bad elongated stars all round the image. Would the 2 inch Baader MPCC coma corrector, in your opinion, be the best way helping solve the problem ?
Ken
Last edited by solissydney; 05-07-2011 at 11:54 AM.
Reason: Adding Image
You might wanna check that the mpcc won't cause it to vignette.
The 5D has a full frame sensor so it has almost the same dimensions as an sbig STL-11000 chip and the mpcc is a t-thread device.
Glad you pointed out the possible problem of vignetting Robin.
After having bought the corrector and taken some images I shall let you know whether vignetting is a problem of any importance
Ken
Thank you Peter.
My choice is the MPCC from Andrew's
Ken
Good choice with the MPCC. It's a good all rounder and you buy it once. Vignetting is very easily taken care of by flat-fielding so it's not really an issue.
The images shows an before and after image of the installation of my new Baader MPCC Coma Corrector on my 12 inch F/5 Newt. using my full frame Canon 5D.
Last edited by solissydney; 07-08-2011 at 06:28 PM.
Reason: adding image
They both still appear to show some coma? Which one is before? M8 or Eta Carinae? Could be the spacing between the camera sensor and MPCC - I know I had to add a spacer to my QSI583 to get it right, still think it's a little out.
Black ring Robin? Where, on which image. Do you mean the black in each corner in the M8?
The M8 came after the MPCC was installed.
Will look into the spacing Troy. Thanks for suggesting that.
Ken
Noticed you're using a 5D DSLR - I'm pretty sure the MPCC was designed, or by accident, to be the "right" spacing for a DSLR with EOS adapter etc. Think it's 56.5mm from memory. How've you got it mounted? EOS adapter straight into camera body, and that screwed directly into the MPCC's T thread?
Troy,
one end of the MPCC is screwed into the T-piece, the other end goes into the focuser.
that way the distance from the C-mos to the first surface of the MPCC is app 55mm.
I intend testing the gap 1 mm at a time.
What think you?
55mm - that's it. My brain was over-complicating it as usual
Sounds right, at least as I understand it, so not sure what's causing that bit of coma still in the corners. I'm getting a little bit still too on my 10", and need to test in 1mm increments as you're suggesting, so sounds like you're on the same path as me. Whether or not that's the right path is another issue...
The black ring is vignetting, and flats should correct it if you can get your flats right. I have 5d MKII and an 8" newt. I notice that with the full frame you can't get the coma corrected across the entire chip, or at least I couldn't. If you extend the mPcc out it gets worse, it's like it needs to be closer to the chip than you can get.
Black ring Robin? Where, on which image. Do you mean the black in each corner in the M8?
The M8 came after the MPCC was installed.
Will look into the spacing Troy. Thanks for suggesting that.
Ken
Yes that one. Was wondering how well flats would work on it.
If the MPCC needs to get closer to the c-mos the only way to do that would be to either file or machine the t-ring to make it slimmer, which I am quite willing to try out.
Ken
Before you machine anything, might pay to check if WR's suggestion above is the problem. ie, is the MPCC designed for full frame sensors, or only crop APS-C sensor sizes etc? I'm not sure and haven't had a chance to check that out yet.
I wouldn't file it down without making sure I could return it to the original using some kind of washer. Actually, I would practice on another t-piece that I have, where it would not matter.
Thanks
Troy pointed out that the MPCC has a spacer ring. However , because the internal tread of the spacer ring has a bigger diameter, by removing it, it is not useful for minimizing the space.