Omega Centaurus

[Lester]

Hi all, this is only 6 x 2 minute exposures taken with Canon 20Da and 14" SCT at F10. I have been getting out of focus stars on the right side of images taken with the Astro 40D, and thought I would try the 20Da to see if the problem was a telescope, imaging train issue or a camera issue. About 2 years ago I did drop the Astro 40D and now think that may have moved the sensor to cause the out of focus stars on the right side.

Does anyone here know how the sensor of these canon cameras is held in place? Any that have modded such cameras may know the answer. I would appreciate your replies, thanks.:thumbsup:

http://i638.photobucket.com/albums/uu109/Lester_045/star%20clusters/9ef69c19.jpg

[RB]

G'day Lester,

Houghy also was concerned about his Astro 40D, saying that he gets elongated stars in one corner.
He suspects it may be something to do with the mod, maybe drop him a PM or he may chime in here.

How's the 20Da, still chugging away ok?

[Lester]

Thanks Andrew for your reply. Yes the 20Da is still a very good camera, just the amp glow that is visible in the bottom right corner.

[RB]

hmmm that's strange, I thought the 20Da switches off the amps during exposure.
Are you sure it's not heat generated from the battery, I use a Canon 240v 'dummy' battery adapter to avoid this.

:shrug:

[Lester]

Hi Andrew, I also use a 240v dummy battery adapter. To my knowledge it is only the later Canon models that do not produce Amp glow.

So your 20Da does not produce any Amp glow? Very interesting.

[gregbradley]

I've modified a couple of 20D's.

There is a black metal frame that screws onto a plate and the sensor is held down with that. The whole unit though is screwed onto body framework as I recall. There probably are photos of the 10D or 350D modification process. The sensor unit hadn't changed much in the first few models. Later on they added the dust remover.
Have a look at those photos.

To get to that point though you have to remove several layers of copper shielding and some ribbon cables.

If it has moved and is not simply sagging in your focuser or your focuser is sagging then you could pack out the offending edge. Working out which corner it is may be tricky.

In your image it is the bottom right. But does that reverse with the camera sensor? Like upside down and reversed like a view through a refractor without a diagonal.

Greg.

[Lester]

Thanks Greg for your reply. This image of Omega is taken with the 20Da and IMO is okay, the problem I have is with the Astro 40D where the right side of all images has stars out of focus. It doesn't matter where the scope is pointing in the sky, as I have gone through a large number of images of different objects and the right side is always the problem. So I am sure it is not a sag problem in the imaging train due to all images having the same problem in the same area.

[Hagar]

Boy that is up close Lester. It is very trying when you have a miss alignment somewhere in the imaging train. The hard part is trying ti find the offending item and fixing it. If it is inside the DSLR I would leave it to an expert rather than stuff it further myself. It wouldn't be the first bit of electronics I have pulled appart and never got to work again.

Good luck with it.

[Lester]

Thanks Doug, I have sent a email to central DS yesterday, but have not had a reply yet. I would not try the job myself, I am better with an angle grinder and welder than fidly electronics, think I may stuff it completely. Either I get Central DS to have a look at it, or leave it like it is, as 80% of the FOV is okay.

All the best.

[RB]

It's been a while now since I've done any astro with the 20Da but I was under the impression that from the 20Da onwards they switched the amps off, I could be wrong.

I'll do some darks at various exposures and let you know.

:)

[Lester]

Thanks Andrew, mine has always produced amp glow, so will be interested to read your results.

Well, well, well, I feel like the boy that cried "wolf", here is an image of Omega centaurus taken last night with the Astro 40D and it is the best I have got for in focus across the FOV. I am at a loss as to the cause now. As for about 2 years the right side has repetedly been out of focus. This image is 16 x 2 minute exposures at ISO 800.

http://i638.photobucket.com/albums/uu109/Lester_045/star%20clusters/dcd5c713.jpg

[RB]

Great to hear the Astro 40D is back to normal Lester.
I know it's a silly question but did you image with something different in the image train?
If you used the SCT every time, maybe something to do with the SCT perhaps?

Anyway great news.

I'll post some darks from the 20Da when I get a chance, now I'm curious to see.

Lovely image BTW.

[desler]

Nothing wrong in your pic that I can see, reminds me of that occasional rattle all cars seem to acquire.

Darren

[RB]

G'day Lester,

Here's a 16 minute Raw dark straight out of the 20Da, ISO 800, no noise reduction, at room temp using the normal battery.
Converted and reduced to jpg for upload.

No real noticeable amp glow there.

How does that compare to yours?

[Lester]

Hi Andrew and Darren, thanks for your comments. Yes Andrew the imaging train was identical, just changed the camera at the end from the 20Da to the Astro 40D.

I can see a hint of amp glow in your dark frame Andrew at the bottom right corner, and that is where mine shows up too. Depending on how much you have stretched/brightened the image, but yours looks very minimal compared to what I would get. Mine would show up a lot after 7 minutes, so your is very good for 16 minutes.

My mentor, Paul H. has suggested it could be a focus issue. I have not used a baltinov mask, still using the old hartman mask for focus.

[RB]

Yep the amp glow is minimal for a 16 min exp. Also I take plenty of darks during my imaging run and as you mentioned using the dummy 240v battery adapter helps even more.

:thumbsup:

[Lester]

Hi Andrew, if I used the 20Da again I would have to go back to taking darks. I have not used darks, etc since using the Astro 40D.

All the best.

[RB]

Ohhh, to not having to take darks, that would be pure bliss........:)