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QHY IMGOH Condensation


philjay

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The other night with a nice high moon I was tempted to take out the IMGOH and do a mosaic of first quarter through my Meade frac.

 

Ive not used this camera for a long time now but it used to play up with condensation regularly but not as bad as the other night.

So I decided to have a look at what can be done to alleviate the problem.

The camera end of the nosepiece is sealed off with an optical window suitably gunged in place but there is no seal or sealant on the nosepiece to camera body plate. Point 1 where damp air can get in.

The camera front plate is not sealed with a gasket or sealant either so point 2 where air can get in.

The camera rear plate is not sealed either, however the plate on which the chip sits has sealant on the wire holes and also there appears to be a hole which has been plugged with sealant. So it would appear that the chip chamber was sealed during manufacture after venting or drying with dry air. But if the front plate aint sealed no wonder it fogs up then freezes. You can see ice crystals forming on the image after 10 minutes it gets that bad.

 

So the answer is to seal the front plate of the camera but how the heck do I vent the chip space with dry air prior to sealing?? Answers on a post card to....?

 

I may seal the whole thing up in a desiccant filled box for a week then have a go at sealing the front plate but the chances of moisture getting in are there when I perform the sealing operation, so some more thought required.

 

Pics showing the chip at start and after 30 seconds. OK I know the chip here is exposed to the air in this shot and its bound to cloud up but this is illustration only and happened when the camera was supposedly sealed. The camera is a few years old BTW so sending it back is not an option.

 

 

Chip  at startstart.jpg?raw=1

 

 

 

Chip after 1 minute

imgoh1min.jpg?raw=1

 

 

 

 

 

 

Edited by philjay
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Not absolutely sure David, the chip and connections are sealed with gunk (silicon sealant I reckon) and all looks to be present and correct under a microscope but I will add some more I reckon just in case.

I'm pretty sure its the fact that the front plate doesnt have a gasket, sealant or even grease on it thats allowing the moist air in. Perhaps when manufactured it was assembled under strict controlled conditions but a few years on and things shift about with use and age and the front plate must have leaked at some point. The camera has been well treated, I dont recollect knocking it or dropping it, I reckon its just age.

When I have dried it out for a week as discussed above I will add seal the front plate and nose piece screws with silicon I reckon.

Making a drying box now.

 

 

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  • 2 weeks later...

Ayup Graham, its in a tupperware box with silica gel packs at the moment. I will have a go at assembling soon once I make up my mind how Im going to seal the front plate. I may just apply a thin smear of silicon grease to the mating surfaces, thats probably the easiest. Easier than silicon sealant anyrode. I still cannot believe there are no seals on these, just relying on machined edges isnt the best idea no wonder qhy had so many condensation problems

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  • 3 weeks later...

Sorted I reckon.

I added more sealant around the nosepiece optical window because it looked a littke susoect. I then left the opened camera in a tupperware box with a big dessicant box for a week or so. I then applied silicon sealant to the face plate and quickly assembled the camera and sealed tge faceplate screws.

 

Just tested the camera and even after 30 minutes, no fogging or icing detected.

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  • 2 years later...

A couple of years on and I tried the imgoh on lunar last evening for the first time since drying it.

Nope, image degradation after a couple of minutes getting worse as time goes on. 

Got to rethink this one

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