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  #21  
Old 19-10-2007, 08:16 PM
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[1ponders] (Paul)
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Here is an image of what happens when I turn the camera off and let it get back to ambient and then turn it back on to -15C. Just a bit of frosting and look at the size of that dust mote. Compare with the second one that had been brought down slowly and allowed to slowly sublimate over about 1/2 to 3/4 of an hour
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  #22  
Old 20-10-2007, 07:27 AM
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[1ponders] (Paul)
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Emailed SBIG last night, received and email this morning, a new ring is on the way. Pretty good service, wot!

BTW those darker marks across the first image, they are there in exactly the same position each time the glass frosts up. they are clearly visible when I look at the chip when frosted. There must be some sort of contaminant on the inside of the glass that the frost collects on.
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  #23  
Old 20-10-2007, 08:01 AM
Dennis
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Hah - call that an ST7 Flat??? This is a real Flat, circa 2003.

Cheers

Dennis
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  #24  
Old 20-10-2007, 08:05 AM
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How did you clean that?????
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  #25  
Old 20-10-2007, 08:16 AM
Dennis
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Hi Paul

I made my own swab based on this DSLR cleaning how to and used PEC pads and Eclipse cleaning fluid. Worked a charm.

Cheers

Dennis
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  #26  
Old 20-10-2007, 08:20 AM
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[1ponders] (Paul)
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I gather they were on the outside of the glass and not on the inside then? I'm wondering where mine is as it is so big. It must be a fair way from the chip surface.

I remember someone posting info somewhere here on how to work out where the dust is based on it's size but I can't find it now.
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  #27  
Old 20-10-2007, 09:03 AM
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An interesting little animation

I was interested in seeing how long it would take for a frosted chip to clear through sublimation so I did a little experiment and here are the results.

I left the camera off for half an hour to reach room temperature and then turned it on and set the temp to -15deg C. Naturally the chip frosted over pretty much immediately. I then left the camera at -15 and took a series of images until it was clear again. It took 40 min to sublimate clear which is handy to know. Anyway here is the animation.
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  #28  
Old 20-10-2007, 10:59 AM
Dennis
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Quote:
Originally Posted by [1ponders] View Post
I gather they were on the outside of the glass and not on the inside then? I'm wondering where mine is as it is so big. It must be a fair way from the chip surface.

I remember someone posting info somewhere here on how to work out where the dust is based on it's size but I can't find it now.
Hi Paul

To remove the dust motes, I removed the large, circular cover plate (including O-ring) and cleaned the glass surface on top of the ccd chip itself, as cleaning the glass window on the cover plate did not remove the marks.

Cheers

Dennis
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  #29  
Old 20-10-2007, 11:06 AM
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I'd say with the size of my spot that my dust mote is on the underside of the glass coverplate. I'll give it a bit of a clean once the new O ring turns up.
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  #30  
Old 22-10-2007, 04:39 PM
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Problem looks like it's fixed. I'll still have to recharge the desiccant plug again, but fingers crossed.

The first shot is 1 min @ 100% cooling immediately after it stabilized at -14°C. No frosting. There is only an outer ring of frosting present. The second shot is from 5 min later and the frost has retreated considerably in that time.

Well on the way to being a very happy chappy. Once the new seal gets here I'll bake the desiccant again, while that is happening I'll replace the seal and dust the inner surface of the faceplate glass window (might replace the seal at work in the airconditioning ).
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  #31  
Old 23-10-2007, 04:27 AM
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Don't be a whimp Paul, like Dennis I have had the cover off the front on one of my SBIGs, it wasn't rocket science even for a Queenslander. As you say, great time to do it as well, when replacing the seal, just don't sneeze.
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  #32  
Old 23-10-2007, 05:57 AM
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I'll bet the hands were shakin' just a bit though Gary

I've had the cover off already to reseat the seal, but I must admit the decision to remove the face plate wasn't made lightly that's for sure with warranty and everything.
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  #33  
Old 23-10-2007, 06:12 AM
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Shakin'? Nope, a few red wines fixed that, LOL. Really though, it wasn't all that bad. I wouldn't put up with dust just becasue of the fear of removing it though.
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  #34  
Old 23-10-2007, 06:32 AM
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I won't have any fears using the fantastic Arctic Butterfly for dust removal. Works a treat on all my other cameras.
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  #35  
Old 26-10-2007, 02:09 PM
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Ok problem solved (I hope permanently).

The first photo was taken on the night of the 22nd before I rebaked the desiccant. A straight drop from ambient to -14 deg in one go. You can clearly see frost around the extremities of the image. The second photo was taken this afternoon with the sweat running off me, very muggy. Ambient at about 25 deg. I dropped the camera temp straight down as far and as fast as it would go, down to just below -10 deg (mine must cool more than the stated 30 deg which is fortunate )

As you can see there is only the slightest trace of frosting in the corners (you may need to flick between the two images). There is no way I could have done this before. When the new seal comes from SBIG I'll just keep it in reserve. If this one is working it will be handy to have an unblemished spare


Added an animation
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Click for full-size image (Cooled - reading -10.5 deg histo adjusted.JPG)
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  #36  
Old 26-10-2007, 03:58 PM
Dennis
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Glad to see your problem with the failing O ring will soon be fixed Paul.

Cheers

Dennis
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  #37  
Old 26-10-2007, 09:42 PM
jase (Jason)
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Ditto

Pleased to hear you're back on track Paul.
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  #38  
Old 27-10-2007, 07:58 AM
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Thanks guys. I've actually gotten a lot out of the experience. I certainly know my way around the CCDSoft Setup dialogu box now and feel much more comfortable with using the camera. Definately a case of "Every frosty cloud has a silver lining"
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