I finally have a Peltier fridge cooling the 5DH on my wide field setup. I replaced the puny fan on the Peltier heat exchanger with a variable speed 0.4A 12V one. I also put a small 60mm fan inside the fridge to blow cool air onto the back of the camera. The peltier junction is supplied by a variable power supply so I can 'set' the cooling temperature.
The following pictures should be self explanatory.
Now thats a interesting setup Bert. Cooled 5dh , temp conpensating focusing plus a 7" tft screen and I suppose it does it all by itself!!!!....oh plus autoguide as well....I tried it abit in summer to peltier cool my 300d and could get close to 10c below ambient which helped alot with noise but my focuser didn`t like all that extra weight. Got some condensation on the bottom of the camera as well as ice on a colder night but didn`t seem to upset the camera..
The screen shows the image generated by the GstarEX on a Canon 18mm to 180mm F1.8 C-mount lens. When the zoom is set to about 30mm the field of view laterally is the same as the 5DH's view. The good thing about this finder I can see all the brighter nebula in real time! Once the object is framed I just simply zoom out to 180mm and the finder becomes the guidescope.
Here is a single exposure for 16 minutes at an ISO of 500 with ICNR on and an Astronomik H Alpha filter.
Fridge temperature 1.0 deg C.
The usual Canon 5DH Canon 300mm F2.8L at f/2.8.
No processing apart from RAW to TIFF and correct for flats and digital development with ImagesPlus. Then levels and curves in PS.
Looking good Bert, and if it eventually doesn't work you can store the cans in there! Although I think you are on a winner - what about introducing some moisture absorption in the case as well to help reduce the possibility of dewing?
I have worked out that the 5DH produces a fair bit of internal heat when taking a long exposure. It is a matter of balance to stop condensation. So far it is fine at 1 deg C. I do not know the temperature of the sensor but it would be higher by a few degrees or more?.
I am already very happy with the results. Why I put the fan inside the fridge was to even out any cooling to not get any cold spots.
It is now just experimenting to see how far I can push it. I have yet to decide whether the dew point is an important parameter or is the system isolated enough not to bother with another complicating factor.
I would not be worried about the dew too much... not during exposure and when the camera is inside the fridge and powered on, because condensations will avoid warmer pars (CCD etc) and go to temp exchanger (cold plate on which peltier is mounted). However, if you take the cold camera inside the warm house.. that will be a very different story.....
Your prediction is correct bojan I have had the fridge down to -12C with ambient at 3C and 100% relative humidity and still no noticeable condensation on the sensor. I know that the sensor heats up while taking long exposures compared to the camera just simply being on. All cold metal surfaces were wet everywhere else.
Will keep adding info in case someone else wants to try it. No sense reinventing the wheel.