DSLR Cooling to Near Ambient with Fan Cooler

[Chris]

There is another possibility - use copper (or aluminium) angle pieces to thermally connect the cold fingers to the mounting plate and hence dovetail and scopes etc.

Good idea:), I dont know about you but my mount etc gets pretty cold so if you can harness this then why not, it would be good to see if it takes the temp down any further?

[Gina]

I might give it a try. All that metalwork sure was cold last night, the dew was dripping off it! My dew heaters worked but needed to be turned up high - the dew was horrendous. I think there may have been dew on the filter in my WF camera - I was getting little halos round the stars later on. Then the mist rolled in.

[Gina]

Here is a diagram of how the box fits to the camera and TEC/cooler.

[Gina]

oooops the above message was posted in error - wrong thread - should have been in the TEC cooling thread

[Gina]

Here is the second wide-field camera finished except for the cooler. I shall try conducting the heat from the cold finger to the aluminium mounting plate and thence to the dovetail etc. That would save having fans and power to them and the weight of fans and fins - the weight of brackets to thermally connect cold fingers to mounting plate will be far lower.

[Gina]

I've had a thought based on taking the cold finger out and onto the mounting plate which means the camera back can be fully functional, including the LCD screen, and that is to bring the cold finger out through the bottom of the camera case. The copper sheet would then be bent round onto the bottom of the camera and be clamped between the camera and the mounting plate with the bolt that goes into the tripod bush.

I'll post a diagram later but the basic idea is to cut a slot in the back casing of the camera where it forms the camera bottom. The cold finger would be an L shaped piece of copper sheet with one part bent over double to go onto the image sensor.

This is only an idea at present and I need to do a proper design and check that it's feasible. I would have to check that it will be possible to assemble the camera for instance.

[Gina]

I have a dilemma now - this thread is about to go off-topic in that I'm going on to use thermal conduction to an aluminium plate attached to the mount dovetail and NO FAN. I was considering starting a new thread but the cold finger mod still applies and this thread isn't too long yet (unlike many of my others )

[Gina]

Here's some photos of my dual wide-field assembly as it is ATM. Not yet finished but I thought I'd take photos now. I have yet to make up a clip to hold the top of the second copper bracket. I also need to make a dew heater for the second 200mm lens. The copper on the back comes from the same 22swg sheet as the cold finger. It makes contact with the cold finger, bends under the camera and is clamped between the camera(s) and the mounting plate. As usual with thermal paste in the joints.

[Cath]

You've certainly been busy Gina!!

Do you get your 200mm lens cheap? .. I'd love a longer lens as I only have the standard 18-55 lens.

[Gina]

Yes,

You've certainly been busy Gina!!

Oh yes, I like playing about with technical things trying to improve my AP equipment in the hope of getting better images with relatively cheap equipment.

Do you get your 200mm lens cheap? .. I'd love a longer lens as I only have the standard 18-55 lens.

Yes, ebay auctions. These are M42 Pentax/Praktica thread as used for film SLRs. I have a few of these lenses from my Pentax Spotmatic but the longest is 135mm. A 55mm f1.8 standard lens came with the camera and I also bought a 35mm f3.5 wide angle lens. I couldn't afford much in those days. I use adapters costing just a few pounds to use M42 thread lenses on Canon EF camera bodies.

These are the ones I bought. The "Super Ozeck Zoom" was wrongly labelled and was actually a 135mm f2.8 prime telephoto. Unfortunately this turned out to have an old style Canon mount that doesn't fit the EF bayonet. It didn't cost much and it might be possible to use it. A "mate" for my old 135mm would be handy. I think there's probably plenty to image out there that's too big for my ED80 and DSLR and NB imaging with Ha and OIII seems to cover most faint fuzzies. I'm also setting up for NB with my ED80 and 1100D (in addition to OSC) with home-made filter wheel and then I'll add SII to Ha and OIII but that's another subject...

[Chris]

Good job Gina:) I'll be very interested to see how this compares to using a fan? How solid is the ali base plate? I know ali is quite maleable and after looking into building a binoscope I've heard it can be quite tricky keeping both optics collimated to each other.

oh yeah, I'm officially in the modding club now:), finished my IR filter removal on my 300D at about 2am this morning, it all seems to be working fine, it certainly was fiddly in places:D

[Gina]

Good job Gina:) I'll be very interested to see how this compares to using a fan?

So shal I Should have some results soon.

How solid is the ali base plate? I know ali is quite maleable and after looking into building a binoscope I've heard it can be quite tricky keeping both optics collimated to each other.

It's 200mm x 100mm x 3mm. I don't think it's going to move much - seems solid.

oh yeah, I'm officially in the modding club now:), finished my IR filter removal on my 300D at about 2am this morning, it all seems to be working fine, it certainly was fiddly in places:D

Well done Yes it is tricky in places. Even though I've had plenty of practice I still have to be very careful - I dropped a screw from the imaging assembly into the works the other day - never found it Just hoping it's stuck somewhere safe and doesn't jam anything up or short anything out

[Gina]

The wide-field setup is now finished except for electric focussing I'll take a photo or two later. Clip made to hold copper plate against coldfinger and dew heater made for 2nd 200mm lens. The focussing system will need a fair amount of thought

[Gina]

More photos... For the moment I've just hot glued a couple of scraps of acrylic onto the focus sleeves on the lenses to provide leverage for manual focussing. I want the assembly ready for use if/when we get some clear night skies. Any remote focussing will take a while to design and make.

[Chris]

Good progess its really taking shape, I take it the two rulers are to help with allignment of both the optics?

I can almost picture you eventually having 4 cameras all lined up doing narrow band or that taking things too far:D

I guess the only worry about losing a screw inside the camera is if it gets into the shutter mechanism? hopefully its lodged at the bottom of the camera somewhere away from the shutter. I lost one of my ribbon cable clips inside the camera last night but eventually it did make an appearance which was lucky, I reckon losing bits in cameras must happen a lot:D

[Gina]

Good progess its really taking shape, I take it the two rulers are to help with allignment of both the optics?

Are you referring to the two acrylic strip? They ease focussing for each lens.

I can almost picture you eventually having 4 cameras all lined up doing narrow band or that taking things too far:D

I only intend to do Ha and OIII. I don't think SII has much to offer but I'm including that with my scope so I'll see.

I guess the only worry about losing a screw inside the camera is if it gets into the shutter mechanism? hopefully its lodged at the bottom of the camera somewhere away from the shutter. I lost one of my ribbon cable clips inside the camera last night but eventually it did make an appearance which was lucky, I reckon losing bits in cameras must happen a lot:D

It's on the other side from the shutter so I don't think it'll get into that.

[Chris]

I see and I see:D

[Gina]

Got the results of tests of the WF camera assembly, in situ :-

First the good news - aligning the cameras physically by measurement puts the image in near enough the same place in both camera sensors

That's it for the good news...

The conductive cooling is nothing like as effective as the fan cooler - one camera showing EXIF T of 17C and the other 14C with an ambient temperature of 10.3C. I think the thermal conduction from cold finger to copper bracket and from there to the ali plate is as good as it's possible to get - plenty of contact area and thermal grease applied. This is disappointing and not what I expected

The focus control is a lot better but moving (even touching) the focus levers causes the star image to wobble quite a lot at full magnification in EOS Utilities. So an electrical/electronic focus system is wanted. I think perhaps this sort of lever with the end linked to a servo might be OK. ATM I'm just going for minimal size star image - I haven't yet made a Bahtinov mask.

The cloud has come in now and with rain forcast, that's it for tonight. I set up for the Cygnus Loop, set guiding going and took a few subs but the noise was evident with just 3m at ISO 3200 let alone my standard 5m. Must do better

Anyway, I've got the answer to my three main questions :-

1. Are the cameras lined up alright? - YES
   
2. Is thermal conduction good enough to cool the cold finger? - NO
   
3. Is a manual lever method good enough for focussing? - NO
   

[Gina]

Just noticed that the photos that were attached to post 114 are no longer there so I'm posting them again...

[Gina]

Some photos of the assembly on the mount.

[Chris]

Well Gina you may be a bit dissapointed but at least you've answered a very worthwhile question:) Also the fans may require power but they don't half look the part strapped to the back of the cameras:D I've got my two fans sitting in the cupboard waiting.

Kudos for doing the experiment!!

[Gina]

Thanks Chris

[Gina]

Assembly back indoors sans lenses, fan cooler retrieved from drawer of old PC stuff. I need to sort out alternative cooler fixing as the old method would interfere with the mounting plate. Either that or drill new holes in the plate so that the cooler can overhang the edge (that might be easier). Then I will need to sort out a cooler for the other camera. Oh well... No chance of any imaging tonight anyway.

[Gina]

BTW the complete assembly with a pair of 200mm f3.5 telephoto lenses weighs in at 2.5Kg

[Gina]

Cooler re-fitted to one camera with original clips and camera moved down to edge of mounting plate. Now to the second one...