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Old 30-12-2010, 12:19 AM
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tempestwizz (Brian)
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Canon 5Dii caveot emptor

Just an advsory note, Bought a Canon 5Dii in Singpore June . On the surface, looked good, but!
Seems to have lmuch ess sensitive area in the lower area of image, as in, a line of lesser responsiveness to light. . This becomes apparent when you do a 'dark'.This deficiency is not evident in general photography, however for our field it is a show -stopper.
Have yet to contact Canon Oz, but will keep interested parties advised.
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Old 30-12-2010, 07:20 PM
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I just got one myself, so please do keep us posted on you findings. Could you post an example of the defect and I will try and replicate it. It could be that yours is a one off.

Thanks
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Old 30-12-2010, 07:45 PM
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Doesn't sound good, I doubt you'll have much luck with Canon Australia, they will only honour warranty on Australian distributor supplied stock.
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Old 30-12-2010, 11:11 PM
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The defect became apparent when making darks and flats. It appears like a dark bar across the bottom of the image frame.
I'll attach a couple of shots. One is a flat (with stars in it) showing lens vignetting, but also a dark band across the bottom. The other is a 5 min dark stretched a bit.
I paid full money for the system in Singapore and it appears to be an international warranty, so, fingers crossed.
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Click for full-size image (Canon_5d_5min_dark.jpg)
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Old 31-12-2010, 07:56 AM
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Omaroo (Chris Malikoff)
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Brian - looking at your exif data, you're on firmware v2.0.4, and mine is on v2.0.8. Maybe it won't fix anything by upgrading, but it's worth a shot given the hassles involved in warranty return. I think that you may have a problem with that, as lenses carry international warranties, but not bodies. I really hope that you can work this out with Canon.

Irrespective, I just took a 300-sec dark at ISO800 (same as your shot) and I have none of the banding problem. In fact, you can see by the position of the levels sliders that I've stretched it all the way and am JUST beginning to see hot pixels.

Dark: 300 sec, manual bulb mode, ISO800 - stretched to the proverbial:
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Old 31-12-2010, 08:49 AM
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It is the shadow of the mirror in the 'up' position, all DSLR's have it. It seems worse with faster lenses or scopes.

It is made more pronounced by light scattering inside the lens or telescope that does not contribute to the image. This is light from outside the area you are imaging that is scattered inside the optic and so lowers contrast.

Below is a flat with my Canon 5D and a poorly baffled 100ED.This was from 2007. I have stretched the image to enhance the contrast.

Bert
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Old 31-12-2010, 09:00 AM
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Here is a flat with the Canon 300mm F2.8L at f/3.6 with external aperture. I have also extended (x2.5) the dew shield or lens hood with an aperture further out. The lens then only 'sees' the area of sky that is being imaged.

The shadow of the mirror is still there but far less pronounced. This image was stretched in contrast as well.

Hope this helps you realize you do not have a dud 5D MII.

Welcome to full frame astrophotography it will test your optics as far as vignetting and flat fields or lack thereof not to mention astigmatism and coma.

Bert
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Old 31-12-2010, 09:30 AM
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Bert - I hear you, but a "dark" is a dark, is it not? Brian's example dark has a very apparent discontinuation, I'm not sure that you can contribute it to mirror shadow, vignetting or light scatter - it appears too pronounced to me. There is no reason that I know of where a proper dark should display these properties. Aperture fully covered - no light. Vignetting aside in the flat example, (yes, welcome to full frame ) shouldn't the "dark" be consistent across the frame edge to edge? I would have thought so - unless there was pretty severe light leakage when Brian's example dark was exposed.

Brian - what's it like if you take another shot with the lens cap on, covered in a black cloth and sitting in a dark cupboard for 300 seconds?

Last edited by Omaroo; 31-12-2010 at 09:44 AM.
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Old 31-12-2010, 09:37 AM
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Chris if his second image is a dark he has a severe light leakage problem. I am sure it is a flat.

Bert
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Old 31-12-2010, 09:45 AM
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Quote:
Originally Posted by avandonk View Post
Chris if his second image is a dark he has a severe light leakage problem. I am sure it is a flat.

Bert
Yep - I agree.

Brian?
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Old 31-12-2010, 10:01 AM
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Which ancient HP calculator gave you that answer Chris?

Bert
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Old 31-12-2010, 10:33 AM
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My HP binary abacus Bert
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Old 31-12-2010, 02:35 PM
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Chaps, The second image is what I though should have been a dark. It was fairly stretched though.
I am currently taking more darks as suggested. Inside a dark-bag.
Bert's explanation for the flat holds water for me, as I had tried earlier to set up my FS-128 with a reducer operating around F5, and basically gave up due to the severe apparent vignetting and the exacerbated dark line across the bottom of the image. I had hoped my move to the FSQ106 would have solved these issues.
It has been difficult to pin things down, as there has been so few evenings when imaging has been possible, mixed with a fair amount of travel for me. Its only been these past few nights when I have been able to get back into the shack.
I will post the results of my 'new' set of darks in a little while.

Thanks for your interest.

Brian
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Old 31-12-2010, 03:45 PM
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As you can now see, my 'new' dark appears to be OK. (Feeling a little foolish now)
I could have sworn the lens cap was on when I was taking darks the other night. Obviously I did not have it on properly, and the light from my control room must have leaked into the front of the lens somehow, although, the band across the bottom is too even for it to be a 'chance' reflection.

Can't see how light could have gotten in via the viewfinder either, although that may have been more possible. If that was the case, then we shouldn't tolerate any background illumination while imaging.

Hence I'm confused, but also relieved that it does not appear to be the major issue I had originally thought.

I'm thankful that Bert covered the issue of mirror shadow. I guess the Tak FS-128 is designed more for visual use rather than imaging. And, as discussed, the issue got a lot worse when I attached the reducer.

Thanks again for your advice/assistance. I wonder what I can confuse myself with next?

Cheers,

Brian
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Old 31-12-2010, 04:14 PM
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Much better Brian
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Old 31-12-2010, 07:05 PM
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Do you put the little cap on the viewfinder when you are imaging and taking darks etc?
Light leak into the viewfinder will produce the effect you have.
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Old 09-01-2011, 07:48 PM
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Hi Brian,

I imaged with a Tak FS152 extensively.

You won't be able to use the FS128 with a reducer and the 2.7 inch focuser and a full frame chip.

You can if you have the 4 inch focuser and a flattener. There was a flattener made for the FS152 it probably works on the FS128. I use it on an AP140 and it works fine.

FSQ106 should not have any problems with a full frame chip. It has a large corrected circle. I forget how large but as I recall it is considerably larger than your 5D's chip.

Basically when using full frame sensors you will need to check the size of the corrected circle otherwise as you have already found out you will get vignetting, coma etc.

Basically you need about 3.5 inch focuser or larger plus a flattener to handle that chip with just about any scope.

Pentax 67 lenses can handle it.

Other lenses probably need to be stopped down to prevent coma and even then that will most likely show through.

Many scopes were designed to handle smaller chips like many Astro dedicated CCDs. Not many have the option to handle the larger ones and unfortunately the ones that do usually are high end and expensive.

Tak, AP, TEC, TMB, RCOS, Planewave handle it for sure.

I doubt a 2 inch focuser on any scope will. Even a 2.7 inch focuser is wishful thinking. Its gotta be 3.5 inch or larger plus a flattener with current optics on the market.

Greg.
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Old 18-01-2011, 08:40 PM
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Hi Brian - saw the same problem with some Cooled/Modded 5D MkII shots on the Central DS gallery
Go to...
http://www.centralds.net/en/index.htm
...navigate to the 'Gallery' - on the top row next to my LMC image(shameless plug!) are 2 shots by Toshiyuki Sugiur taken with an Astro 5D MkII.
I think you can see the banding at the bottom of the thumbnail image.
Looks like a common problem - that's a hell of a big area to crop out!
Cheers
Doug

Last edited by dugnsuz; 18-01-2011 at 08:55 PM.
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