All Sky Camera Revisited

[Gina]

Well, surprisingly it seems to be better, the temperature has dropped to 11°C.  Room temperature same and I don't think anything else is different though the thermal contact to the TEC could have changed, I guess, maybe squeezed the thermal paste out a bit...  Dunno!

[Gina]

Thought I'd try continuous exposures to see if imaging made any difference to the temperature - it didn't - steady at 11°C.  Turned out the lights and ran a sequence of 30s exposures.

[Jonk]

I think that continuous 20fps or similar will give you the warmest camera insides.

The sensor doesn't warm up when just being exposed, only when it's reading the pixels... I'm assuming this from my tests as the temperature rose when I did this vs longer exposure times.

[Gina]

Have the Nofan perched on three blocks 50mm above the table which should improve airflow through it.

[Gina]

After setting it all up again it's got down to 11°C and seems to have stopped getting any cooler.

[Gina]

Crept down another degree.

[Gina]

For completeness I'm going to try the large aluminium passive cooler supported the same way.

[Gina]

Huge difference - only gone down to 21°C and the cooler is very hot - barely touchable, probably 70°C.

Conclusion :-  Without a fan and air duct, the Nofan beats the Artic Alpine 11 Passive cooler into the dust!! 

The Artic passive cooler works alright with active airflow through it but so do much cheaper finned coolers.

Edited October 20, 2019 by Gina

[Gina]

Looking out of the living room window - cropped.

[Gina]

[Gina]

Part of the sky - screenshot of part of my ASC image looking through my living room window roughly south.  Solid cloud!!  60s exposure with zero gain setting and camera temperature of 9.5°C.  This is zoomed in more than pixel resolution.   No dome but a less than perfectly clean window.  Ambient temperature is about 19°C indoors - be a lot lower when ASC is outdoors.

Edited October 20, 2019 by Gina

[Gina]

Trying to work out the ASC outer casing and sealing to the Nofan whilst obstructing airflow through it as little as possible.

Meanwhile, I have been searching through all the methods of CPU cooling.  I thought I had found another alternative in liquid cooling (not water cooling) in a compact, all in one, ready made liquid cooler - a sealed unit without a separate reservoir (the main problem with my DIY water cooling system). 

viz.  Cooler Master MasterLiquid Lite 120 Liquid CPU Cooler

However is seems the pump is in the "waterblock" which would cause vibration (though how much I don't know).  The main picture doesn't show any wires but the shot of the PC with unit installed seems to show a cable from the "waterblock".

[upahill]

3 hours ago, Gina said:

Trying to work out the ASC outer casing and sealing to the Nofan whilst obstructing airflow through it as little as possible.

Meanwhile, I have been searching through all the methods of CPU cooling.  I thought I had found another alternative in liquid cooling (not water cooling) in a compact, all in one, ready made liquid cooler - a sealed unit without a separate reservoir (the main problem with my DIY water cooling system). 

viz.  Cooler Master MasterLiquid Lite 120 Liquid CPU Cooler

However is seems the pump is in the "waterblock" which would cause vibration (though how much I don't know).  The main picture doesn't show any wires but the shot of the PC with unit installed seems to show a cable from the "waterblock".

Yes the pump is in the waterblock, and controlled from the CPU fan header usually, if its PWM controlable you could rig something up to reduce the pump speed and reduce vibration.

 

[CedricTheBrave]

I took my ZWO ASI290M apart last night (just being nosy) and there are big gaps behind the sensor so its not attached in anyway to the housing. I cant help thinking that it would help cooling if there was some transfer material behind the sensor and the circuit board so there was direct contact to the alloy housing. Not sure if anyone has looked at a cooled version to compare.

[Chriske]

To dampen vibration why not use silent-blocks between fan and coolingblock..?

[Gina]

45 minutes ago, Chriske said:

To dampen vibration why not use silent-blocks between fan and coolingblock..?

It's not the fan that's that problem, that unit would be mounted on the ROR - the problem is the pump in the "waterblock" that would be attached via the Peltier TEC to the camera.

[Gina]

1 hour ago, CedricTheBrave said:

I took my ZWO ASI290M apart last night (just being nosy) and there are big gaps behind the sensor so its not attached in anyway to the housing. I cant help thinking that it would help cooling if there was some transfer material behind the sensor and the circuit board so there was direct contact to the alloy housing. Not sure if anyone has looked at a cooled version to compare.

You're quite right, cooling the camera housing only cools the air inside and is a very inefficient way of cooling the sensor but it does seem adequate if the housing is cooled sufficiently.  The construction of the cooled cameras must be totally different as they incorporate a dual stage Peltier TEC cooler between sensor and the back plate, which is attached to fins in the main body of the casing.

[Gina]

I've looked inside the ASI178 cameras and the space between the imaging board and main board is only a mm or maybe two.  No room for a plate to go out to the casing.  The only way to get cooling directly to the back of the imaging board would be to rehouse the camera.  I looked into doing just that but can't see how to get the main board out of the housing - the connectors hold it in.  I'm left with either just cooling the casing or forking out for a proper cooled camera at around £600 which I can't afford.

[Gina]

Correction on price of cooled astro camera.  Cheapest on FLO is £799 + carriage and that's a colour version.  Cheapest mono camera is £999 + carriage ie. over a grand!!!

[pete_l]

5 minutes ago, Gina said:

Cheapest mono camera is £999 + carriage ie. over a grand!!!

You can buy a new mono QHY6 from a UK supplier for considerably less than that

[Gina]

The problem with the QHY6 is it's very small sensor - 1/3".  To cover the sky with the fisheye lens I have needs a 1/2" sensor.  I have tried in the past to get a fisheye lens with 180° coverage with a 1/3" sensor, without any luck. 

[Gina]

Still thinking about the cooling of the hot side of the TEC.  The Nofan would seem to be adequate but attaching it to the casing with a good seal is not easy.  Water cooling is still looking interesting and with the waterblock I have, sealing would be no problem.  Sealing the outer housing has always been the main problem.  This leads me to think again about water cooling.  I have used water cooling in the past to cool a DSLR for imaging and also for cooling the hotend in my Giant 3D printer.  I have a radiator and fan plus circulating pump that I've used in the past.

There is plenty of room in the apex of my ROR for inside equipment so arranging a small reservoir, pump and radiator would not be that much of a problem.  What I do know is that water cooling is the most efficient way of cooling I have come across.  I once set up water cooling for a tower PC using a passive cooler external to the PC.  the passive cooler included a pump which was virtually silent so I had a noise free PC.  The passive radiator is quite large and heavy so not suitable for mounting in the observatory ROR.

[Gina]

I'm thinking of going back to the IP65 box for the outer casing (with the waterblock) I was looking at before.  Should be able to seal this box and keep the damp out.  See THIS PAGE of this thread starting at the post of June 26.  I rejected this box before due to difficulty of mounting it on the mast but it can quite easily go on the ROR apex.  The cooling radiator etc. for the water cooling can fit in the roof apex inside.

These images show the observatory and a previous ASC mounted on the ROR apex.  I can design and print brackets to attach the new box to the barge boards.  The RPi and all electronics will be in the box and use WiFi communications.  The water pipes will go up under a barge board and into the roof space.

 

Edited October 25, 2019 by Gina

[Gina]

This is a post from back in the summer showing the RPi and HAT plus camera unit with earlier thermal jacket.  The latter will be replaced with the much bigger printed jacket.  I don't expect to use the remote focussing.

On 28/06/2019 at 23:16, Gina said:

New camera support is fine and the lens is at the correct height in the dome.   Have camera unit installed with Peltier TEC and waterblock with water pipes connected.  Been connecting up but more to do.

Edited October 25, 2019 by Gina

[Gina]

Decided to go for my own water cooling system with the 40mm x 40mm x 10mm copper waterblock, 80mm radiator and fan, little aquarium pump and 3D printed reservoir with submerged pump in the bottom.  These will all fit on the south wall of the ROR and don't need to be right at the top making fitting easier (and safer).  The pump has a 3m head so no problem with that.  The 80mm fan is inaudible at more than a foot away - the pump is pretty quiet too, no that it matters much - I won't be in the observatory much.

A couple of screenshots from CAD models - thermal jacket for camera and water cooling reservoir.

 

Edited October 26, 2019 by Gina