Modded camera problems

[paul11]

Hi all can anyone take a guess at what’s going on in these images. I’ve just modded my 30D and did not replace the filter and I’m getting strange results. Setup is 200mm newt 30D 2” T Piece clip filter MPCC PHD. In the single star image I’ve got a double reflection could it be collimation?. And in the M42 image I can see a tunnel effect, I’ve never seen this before the mod,,,Paul.

[Psychobilly]

First one...

I guess somethings not sitting square to the optical axis causing the reflection...

Dont know where that level of vignetting is coming from but if you can post a quick pic of the setup that you fit into the focusser...

Never used an MPCC so I am hoping someone who does will be along to help...

Are you using the MPCC properly...

like this ...

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

Peter...

[paul11]

Thanks for trying to help,the MPCC is fitted the same as your link,i could remove it and see what happens.

[Psychobilly]

I found the MPCC data sheet and thought it might be easier than you taking pics..

I didnt quite get what you meant by this

"Setup is 200mm newt 30D 2” T Piece clip filter MPCC"...

Seeing as the MPCC fits diirectly into the t mount on the camera body. and then into the 2" focusser drawtube...

The clip filter is an EOS Clip in one in the camera body?

I honestly cant see how removing the "hot mirror" IR blocking filter off the front of the Cameras sensor or the Clip in filter would introduce this severe vignetting... thats why I wondered about how the MPCC was connected to the camerra...

Steppen wolf ... where are you...?

Peter...

[paul11]

When i listed the the Camera and T piece they were not in order, the M42 i have posted in Deepsky imaging is with the same setup pre mod and yes the clip filter is in the camera body,,,Paul.

[steppenwolf]

This does not appear to be a collimation issue, more a reflection problem. I use an MPCC with an 8" Newtonian and find that it works very well indeed on my astro CCD camera BUT, I have my filter (IDAS LP filter) attached to the telescope end of the MPCC.

I suspect that the first problem is a reflection between the clip filter and the MPCC so I would do a test image with the filter removed, then another with the filter in place and the MPCC removed and a final one with both filter and MPCC removed but I think it is the filter that is giving the problem.

The vignetting looks very tight - there does not seem to be much of a gentle gradient, it is more like looking through a porthole which is an effect I certainly don't get with my 8" Newtonian although I certainly get vignetting to some extent. Again, this could be a reflection problem exaggerating the real vignetting that I would expect to see.

[paul11]

Thanks a lot guys i will do some tests and let you know the results, do you think putting a baader filter back in the camera could help,,,Paul.

[Psychobilly]

I still cant see how removing the filter can cause these issues...

Peter...

[Merlin66]

Whatever the problem, IMHO it's nothing to do with the filter removal. I have a pair of 300D's one with the Baader filter and one without the filter...There's no difference in performance other than the red response....

The vignetting looks very pronounced; you infer that using the set up prior to filter removal that it was OK? What else changed????

Ken

[steppenwolf]

I am with Peter and Ken on this, the removal of the IR blocking filter is not part of the equation, I am sure.

[paul11]

I’ve just had a look through some pre mod images and I can see some vignetting but not as bad, and as for the reflection I cant see it in any other images. The Met says it’s clear tomorrow so I will do some tests,what is the cause of vignetting?

[Merlin66]

Something is causing an obstruction in the light beam between the main mirror and the CCD chip.

Could be anything:rolleyes:

I'd start by looking at the various clear diameters of the adaptors, filters, focuser, secondary mirror etc.....

[paul11]

I got a bad feeling my secondary mirror could be a bit small 45mm, in the NEWT programme when I designed it the secondary can be between 45-60mm and does not show and vignetting at the focuser. What size secondary mirrors are in your newts?,,,Paul.