Cooled Astro Cam Conversion

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Cooled Astro Cam Conversion

This topic has 18 replies, 10 voices, and was last updated 21 September 2019 at 22:39 by Michael Gilligan.

Viewing 19 posts - 1 through 19 (of 19 total)

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31 August 2019 at 14:12 #31271
Neil Wyatt
Moderator
@neilwyatt
As it’s been guessed, let’s make this a build log.
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31 August 2019 at 14:12 #426793
Neil Wyatt
Moderator
@neilwyatt
Ok, plenty of people will be able to guess the general idea, but armed with a vague idea of my interests can you give a more than just a name to this part?

Clues – the two parts are an interference fit and pressed together in the vice before finishing the central part. There are two more threaded holes to be added either side of the column and in the finished project this will be totally hidden from sight.

Neil

Strange distortion on the phone camera, those holes are diametrically opposed!

Edited By Neil Wyatt on 31/08/2019 14:14:01
31 August 2019 at 14:52 #426805
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Neil Wyatt on 31/08/2019 14:12:44:

… armed with a vague idea of my interests can you give a more than just a name to this part?

It's an Industrial Grade Nipple Shield.
31 August 2019 at 15:24 #426811
Brian Sweeting 2
Participant
@briansweeting2
A telescope pivot?
31 August 2019 at 15:32 #426814
peak4
Participant
@peak4
Considering an interference fit with the copper item; is it a heater to combat dew forming in a telescope?

Bill
31 August 2019 at 15:36 #426816
Arthur Sixsmith
Participant
@arthursixsmith43623
Guitar effects peddle?
31 August 2019 at 15:36 #426817
Nicholas Farr
Participant
@nicholasfarr14254
Hi, it's a base for a rotating space camera/telescope which is due to be taken up to the ISS on the next launch and then one of the astronauts will do a space walk and weld it somewhere on the outside.

Regards Nick.

Edited By Nicholas Farr on 31/08/2019 15:37:25
31 August 2019 at 16:19 #426824
Michael Gilligan
Participant
@michaelgilligan61133
Posted by peak4 on 31/08/2019 15:32:42:

Considering an interference fit with the copper item; is it a heater to combat dew forming in a telescope?

.

With similar, but inverted logic … is it a cooling stub for a camera ?

MichaelG.
31 August 2019 at 16:29 #426830
Joseph Noci 1
Participant
@josephnoci1
Posted by Michael Gilligan on 31/08/2019 16:19:30:

Posted by peak4 on 31/08/2019 15:32:42:

Considering an interference fit with the copper item; is it a heater to combat dew forming in a telescope?

.

With similar, but inverted logic … is it a cooling stub for a camera ?

MichaelG.

Michael's got it…To cool the sensor.

Joe
31 August 2019 at 16:30 #426831
Robert Atkinson 2
Participant
@robertatkinson2
Plus one for camera CCD cooling. Called a "cold finger" .

Biggest issue with coolled LCDs is keeping condensation off the electronics. Hermetic + vacuum with bit of dessicant is ideal but hard to acheive. A separate container with replaceable large (0,5kg) silica gel bag piped to a reasonably well sealled camera head is a good compromise.

Robert G8RPI.
1 September 2019 at 14:45 #426951
Neil Wyatt
Moderator
@neilwyatt
Michael, Joe and Robert have it.

It's for a 'Toupcam Mono', a very simple mono camera with a small sensor, normally the sensor sits on top of a 'stalk' that is moulded into the case, quite a neat arrangement but only basic passive cooling.

If I cool to zero or below it I will be able to take long exposures with little noise. It will fit on a cheap peltier and heatsink/fan module in place of the small internal fan and heatsink.

I'm 3D printing a 2nd prototype case, obviously plastic with a honeycomb of air inside is a good choice for insulation, with some strategically placed foam above the body of the heatsink.

The final design will need to include a t-thread to attach and adaptor and perhaps a storage space for a silca gel sachet.

Why bother with a tiny webcam sized chip? Well I have a filter wheel and RGB filters (as well as some specialist ones for planetary imaging) but a large-chip mono camera is expensive, especially if cooled. It's also a lot more involved to do mono imaging so this will let me see how I get on with it without having to make a big investment, although I will be limited to small targets.

If all goes well I can contemplate bigger investment… or just specialise in imaging tiny but challenging subjects!
1 September 2019 at 15:07 #426953
Joseph Noci 1
Participant
@josephnoci1
Won't the fan vibration blur the image a little, esp during long exposures?
1 September 2019 at 15:53 #426968
Robert Atkinson 2
Participant
@robertatkinson2
Joseph akes a good point about fan vibration.. Another issue is the high energy density and thermal gradient of small peltiers. Have you considered liquid cooling? just small pump and tank would be enough, you probably don't even need a heat exchanger if the tank has reasonable capacity and surface area.

Robert G8RPI.
1 September 2019 at 16:13 #426974
duncan webster 1
Participant
@duncanwebster1
Do you need a pump? Thermo-syphon might work, then no vibration
7 September 2019 at 19:10 #427944
Neil Wyatt
Moderator
@neilwyatt
Posted by Joseph Noci 1 on 01/09/2019 15:07:16:

Won't the fan vibration blur the image a little, esp during long exposures?

A question many have asked. No-one has ever been able to demonstrate a measurable effect. Does make sense to use sleeve bearing fans though, which have negligible vibration.

Edited By Neil Wyatt on 07/09/2019 19:12:54
7 September 2019 at 19:11 #427945
Neil Wyatt
Moderator
@neilwyatt
Posted by Robert Atkinson 2 on 01/09/2019 15:53:45:

Joseph akes a good point about fan vibration.. Another issue is the high energy density and thermal gradient of small peltiers. Have you considered liquid cooling? just small pump and tank would be enough, you probably don't even need a heat exchanger if the tank has reasonable capacity and surface area.

Robert G8RPI.

It's been thought of, but it would probably need to be a water glycol mix, working well below zero.

Simplicity and reliability are prime considerations, though.
7 September 2019 at 19:21 #427947
Neil Wyatt
Moderator
@neilwyatt
Current iteration. Designed to have a Canon ET to T-thread adaptor glued in the end to give the same back-focus distance as a DSLR so it can be swapped across without re-focusing and used with field flattener/coma corrector (although these are probably uneccessary with such a small chip it makes things easier = more reliable).

I did a little test of the camera on the 'Pillars of Creation', uncooled and the sensor was more than a bit grubby after my experiments, plus not a lot of integration time (software problems left me living with mostly 7.5 second exposures).

So probably not the best ever:

To compare, this is with my modded DSLR and I'd class this as a 'record' image. Note the smaller image scale with bigger pixels:

The scruffy image shows a lot more detail, so it's worth pursuing this.

Edited By Neil Wyatt on 07/09/2019 19:23:45
21 September 2019 at 21:48 #429921
Neil Wyatt
Moderator
@neilwyatt
Some photos (linked from an astro site – SGL – because it's easier!) to show construction of the camera combining machine parts, 3D printed bits and off the shelf components.

Finished cam, photo a bit shaky!

Inside the boxes:

Heatsink ready to fit:

Most bits of the original camera:

10 minute 'dark' exposure at 25C (i.e. with the camera covered) and no cooling:

10 minute dark exposure after having the cooling switched on for a few minutes:

I think it's easy to see how this will help with imaging faint objects!

Neil
21 September 2019 at 22:39 #429925
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Neil Wyatt on 21/09/2019 21:48:35:

[ … ]

10 minute 'dark' exposure at 25C (i.e. with the camera covered) and no cooling:

10 minute dark exposure after having the cooling switched on for a few minutes:

I think it's easy to see how this will help with imaging faint objects!

Neil

.

That's certainly encouraging, Neil

MichaelG.
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