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Corpze

Peltier cooled ZWO ASI 120 MC

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I certainly see some multi-coloured noise from my ASI120MC.

James

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Is the ASI ZWO camera meant to operate at sub -5 degree temperatures?

Working Temperature: -5°C—45°C
Storage Temperature: -20°C—60°C
Working Relative Humidity: 20%—80%
Storage Relative Humidity: 20%—95%

James

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I'm all for moving the large heatsink and fan away from the camera and use pipe/liquid to move the heat from camera to heatsink. It would remove the fan vibration problem and all that weight from the one place you do not want it.

If I had a proper camera like you guys that's definitely how I'd be doing it.

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I played with a USB-powered weak Peltier on some cameras. It did help a bit, but it wasn't powerful enough to make the camera very cold. And it seems like it's cooled camera time, as for example iNova launched Peltier units to their cameras: http://www.m42optic.fr/pro/catalog/newsdesk_info.php?newsdesk_id=44 - handy that it's for existing cameras.

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Guys I don't mean to hijack the thread, but all the test with the cooling system seems to be between 5-15s. If I plan to use my ASI120MC for planetary use only, meaning there will be lot shorter exposures, something like 30ms, would it still worth the trouble to cool it. Would it make any difference in that area?

I use Firecapture to record and I did notice that when it is winter (sensor temp is around 3-4 C) it records less noise, it even says it in the recorded txt file with the avi. But I don't know if it has any effect on the outcome. I also know that stacking more frames yields less noise at the end, but say stacking more of the less noisy frames?...

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No need whatsoever to contemplate cooling for planetary. Cooling is more for the ppl wanting to push the boundaries of that the cams are capable of.

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I've been following this with interest as I've been doing some experimenting with cooling too, having had a go at some longer exposures of small planetary nebulae with the ASI120MM over the Summer. I got a fan, heatsink and peltier from a friend who ripped it out of a battery fridge to cool his DSLR. None of the parts had been separated, so all I did was bolt the fan to the heatsink to do some tests in the garden. The aluminium block on the bottom of the peltier was simply rested on the case of the ASI for the test. I added three thin layers of foam insulation around the camera.

post-20257-0-06989600-1415475287.jpg

Ambient temperature was 20 degrees C, and once started up, the camera temperature was 30 deg C. I started the peltier and fan, and watched as the temperature dropped, levelling off about 11 deg C. Considering the crude test set up, I was quite pleased with a 20 degree temperature drop on the sensor.

post-20257-0-20805900-1415475663_thumb.j

I tried the camera that night on the Moon. I simply used elastic bands to hold the cooling assembly on to the camera. I figured if it worked reasonably well, I could refine the design into something lighter and less messy. Night time temperatures were lower, and as a result, I got the sensor down to 4.5 deg C. Even though I wasn't shooting long exposures, the noise did seem reduced when assembling this mosaic. My only problem was fan vibration, so I ended up cooling, switching off, capturing the AVI, then switching the cooling back on before the next AVI. It was quite a damp night and I also fogged up the barlow as it got so cold!

post-20257-0-49847600-1415476179_thumb.j

Encouraged by the temperature drop and noise reduction, I decided a revised version would be the next step, but rather than fan cooled, I was going for water cooling, removing much of the weight from the camera. The bits just arrived  today, 'though I'm still waiting for some hose. The peltier will go directly on the back of the camera, with the blue water cooling heatsink on the back of that. The aluminium disc will be drilled to match the holes in the back of the camera so some long bolts can clamp all these parts together. A water pump and fan cooled radiator will then be located off the scope and tripod, preventing any vibration. I should be able to control the temperature via the peltier, pump speed and fan speed.

post-20257-0-30303500-1415476476.jpg

I'll report back once version 2 is up and running.

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The last of the bits and pieces I needed arrived today, so this evening, I assembled my cooled ASI120MM. I balanced all the parts for the test, and if successful, I'd make a permanent carrier for the water tank, radiator and pump. For now, this would do. I switched the camera on doing a 30FPS preview and let it warm to its ambient temperature which was 33 degrees C. Room ambient was 22.5C.

post-20257-0-33973000-1416022322.jpg

Next I switched on the peltier, fan/radiator and pump, and within 6 minutes, the camera sensor temperature had dropped to 10C, with a drop to 9.3C after another 4 minutes.

Ignor all the boxes and other junk to balance it all. I'll be refining that into one container to support a water tank, pump and fan, and of course the camera will be mounted in the scope, not balanced on a pot!

post-20257-0-75669600-1416022473.jpg

I spent the rest of the evening and night, until 3am, doing various tests of gain, exposure etc, monitoring the temperature and video captured. These two screen captures are 1 minute exposures, gain at 50, both uncooled at 20C and cooled at 4.5C. The noise difference is staggering!

post-20257-0-16262400-1416022579_thumb.j

Finally a shot of the camera and filter wheel, with the insulation redone to cover the whole of the camera body. Many thanks to 'Corpze' for starting this thread and inspiring me to have a go myself. I think it's going to be fun experimenting with it, and I hope it will also improve my Solar images, when the sensor hits 40C and above.

post-20257-0-39747400-1416022682.jpg

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Very nice indeed, is there any control to the cooling or is it all or nothing?

I have an old water cooling system for a PC that would probably work much like that. Do you plan to connect the water pipes after slewing? I would be worried about the mess it would make if they get caught as they aren't as easy to handle as wires.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

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I have a 12v LED dimmer which controls the peltier, so controlling the amount of cooling. The PVC water pipes are very soft, and more flexible than the USB cable to the camera, so I don't see them causing any issue when slewing. The only thing I will have to watch out for is them twisting and kinking, preventing water flow. It's a very light weight system ( at the camera end ), so I won't be putting undue stress on the focusser which has been raised much earlier in this thread.

 

No need whatsoever to contemplate cooling for planetary. Cooling is more for the ppl wanting to push the boundaries of that the cams are capable of.

I think it will have benefits for planetary. I've noticed particularly on Jupiter, where you are forced to capture shorter runs due to rotation, that each channel can be noisy due to the limited number of frames. Planets like Saturn, Uranus and Neptune, often have slow frame rates, so reducing noise here is also worth while.

Even on the Moon, reducing noise could mean fewer frames needed, speeding up mosaics. I spent 6 hours capturing a 119 panel mosaic of the Moon earlier this year, shooting 2500 per panel. If I could have got less noise shooting 1500 frames cooled, it would have made the process much faster, and certainly for the Sun, where the sensor gets very hot, I've seen lots of noise.

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On very short exposures read noise is dominant and cooling won't limit it. It may however start limiting FPN a bit and more as the exposure time increases and dark current starts to be the major noise contributor.

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This is the main reason for cooling my ASI120; I really like the little planetary nebulae. This is 300 x 2 second guided exposures for luminance, and 100 x 2 seconds for each of the RGB filters. I didn't quite get the RGB lined up correctly when putting it together, but from memory, it was 2:30am and I had cold fingers! but the ASI has revealed quite a bit of structure within this tiny target. Can't wait to try with cooling.

Saturn Nebula

ngc7009b.jpg

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Made a carrier for the water tank and radiator today. It just needs a final sand and a varnish to protect it from the damp.

post-20257-0-17160800-1416067030.jpg

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Looks like an interesting project, Stephen.  Fogging up the optics because they're so cold could be something of a nuisance though :)

James

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I think that was just because it was such a humid night, somewhere around 80 to 90% from memory, and I can control how cold it gets via the LED dimmer.

Edited by ArmyAirForce

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I was surprised the Barlow fogged, but the filters in the filter wheel, next to the camera, didn't. Perhaps it was because the barlow was next to the warmer air in the scope.

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I was using my cooled ASI 120 MM a few nights back and got the sensor temperature down to about -9. Limitations on exposure at that temperare was definitely the skyglow from the moon rather than noise from the camera - 2 to 3 minute subs looked very reasonable.

It was a damp evening, and by the end of the session the camera had about 2mm of frost on the outside. No problem with the sensor fogging up though, although dew on the objective was why I packed up in the end.

Must add some insulation round the body of the camera - should help get the temperature down further and reduce frosting problems!

cheers,

Robin

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In the camera specs, it says -5C as a minimum operating temperature. Have you encountered any problems going as low as -9C?

Edited by ArmyAirForce

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Frost may be common as the whole case is cooled (while in DS Cameras not, only the sensor), which cools the front cover window and boom. I used a simple USB powered Peltier, but I'm not sure if some minimal shakes from the fan aren't passed on the camera. I'm curious what QHY will do with miniCAM-5s. And maybe someone will make cooled "planetary" IMX249 camera :)

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There is room inside the ASI 120 for some small desiccant packs which may help if the sensor is frosting up. It's also really easy to open as I've found I have to make sure I hold the front of the camera when unscrewing it or I end up leaving the front of the camera attached to the scope.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

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In the camera specs, it says -5C as a minimum operating temperature. Have you encountered any problems going as low as -9C?

I didn't see any issues with the lower temperature. Too cold is not normally nearly such a problem as being too hot - especially it's unlikely to give any lasting problems. I recall dipping a pocket calculator in liquid nitrogen as a student - it didn't work at all at -190C, but as it warmed up it started to work again, it just took about 30 seconds to do each calculation. Once back to room temperature it was back to normal...

cheers,

Robin

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I saw this article a while ago and as I has a ZWO ASI120MC camera that I was trying to use for longer exposures I decided to have a go. Here is the solution that I came up with:

 

The current camera back has extra M4 mounting screw holes with at 39mm spacing, giving a 55mm diagonal spacing

sml_gallery_43946_3761_41429.jpg
 
I found on ebay cheap Peltier TEC and graphics card cooling fans, so with a little wiring, heat shrink tubing and some thermal paste the two are now combined
sml_gallery_43946_3761_141689.jpg sml_gallery_43946_3761_65841.jpg
 
To help keep the temperature of the camera more stable I got some 6mm closed cell foam and made a little jacket for it
sml_gallery_43946_3761_144855.jpg
 
The Jacket in place:
sml_gallery_43946_3761_13078.jpg
 
This is what it looks like when mounted in my LX90. I think its a very neat solution.
sml_gallery_43946_3761_64861.jpg
 
No cooling, 70% Gain 30 second exposure - 26.8°C
sml_gallery_43946_3761_206311.jpg
5 minutes of cooling, 70% Gain 30 second exposure - 10.2°C (temperature Delta 16°C, lowest temperature obtained outside so far -2.3°C)

5 minutes of cooling, 70% Gain 30 second exposure - 10.2°C (temperature Delta 16°C, lowest temperature obtained outside so far -2.3°C)

The whole thing adds only 101g to the camera giving a total weight of 237g. The whole rig requires 12v and pulls just over 2.5A. I'm driving it with a 6A power supply that is a spare supply for powering my scope.
The whole little exercise cost:
Peltier:                               £  3.24
Fan:                                   £  4.02
Foam Sheet:                     £   3.00
Connectors and misc bits: £  2.00
Power Supply:                   £12.00
Total Cost:                        £ 24.26
The whole thing works rather well for a planetary camera being made to do something that its not best suited to and the fan seems to cope well with the heat output by the Peltier
It does not introduce any noticeable vibration to the telescope although the fan although quiet is a little noisy, but when its so quiet outside any noise is noticeable.
The only thing that I think I would like to add to this is perhaps a basic controller to allow control over the fan and peltier. The main issue that I have found is that condensation/ice can build up underneath the jacket and so you need to remove it after to ensure no water builds up under it and the camera is dry. I may well try running it without the jacket to see if it is really having any beneficial effect.
 
Hope this is of interest.
 
Mark
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