I've ordered some colour changing silica gel bags for the outer chamber.  The inner (around the camera) can have one or two of those little ones that come with goods.  There is very little room round the camera, it will have to go beside the USB plug.

This photo show how big even the smallest silica gel bag looks beside this little camera.

Screenshots of the CAD models for the two parts of the camera enclosure.  The square hole in the bottom takes the Peltier TEC with it's two wires in the slots.  The semi-circular notch in the side wall takes the USB cable in conjunction with the top part.

If these fit the camera alright, the next thing will be a clamping system to hold the camera against the Peltier TEC via the casing and holding the two camera casing parts together.

Here a photo of the camera in the bottom of the casing with the silica gel bag squashed into the gap.  Actually, this photo shows that I have allowed more space for the USB plug than needed so I'll change it as I want no more air in the cold chamber than needed.

The larger silica gel bags have arrived.

I wondering whether to use some of the new silica gel crystals from one of the bags and put those in the space inside the camera enclosure rather than using a tiny silica gel bag (that I don't really know the state of).  The top part of the casing could have a hole through to the inside which would be sealed with a plug or cork.  This would mean not only being sure of fresh silica gel but fill all the spare space.

Decided the NEMA14 stepper motor I used before was overkill as well as taking up a lot of space so I'm replacing it with the ubiquitous 28BYJ-48 mini stepper motor modified for bipolar operation.  This is much easier to mount and in this application, one screw is sufficient as it sits nicely into the curve of the camera casing.  It will need a new pinion plus a spur gear on the lens shaft.  This provides focussing using the thread of the lens mount (the lens has no focus mechanism).

2 hours ago, Gina said:

This provides focussing using the thread of the lens mount (the lens has no focus mechanism).

Be warned, some lenses will hit the sensor of the ASI 120 models if screwed in too far! May be worth adding a ring below the lens to stall the stepper if the focus routine tries to run the lens too far.

There is already a 5mm thick adapter to convert C to CS mount so no problem there.

Here is part of a screenshot of the KStars FITS Viewer with the camera looking out of the living room window to the south.  No cooling - I'm going to set that up next.  Camera temperature is 13.2°C so camera image is showing plenty of noise and hot pixels.

Mine responds very well to darks for those hot pixels.

Moved ASC outside onto the window sill.  It's now slowly cooling down towards outdoor ambient.  I realised that I'm not ready for cooling as the camera needs clamping onto the Peltier TEC.

7 minutes ago, Stub Mandrel said:

Mine responds very well to darks for those hot pixels.

Darks are a problem as the lens doesn't have a shutter or aperture control.

Camera temperature has dropped to just over 2°C.  Part of image - 10s exposure, gain of 50.

Camera temperature has now dropped to just over 1°C.  Part of image - 30s exposure, gain of 50.

Camera temperature has now dropped below 1°C.  Part of image - 30s exposure, gain of 50.

Camera temperature has now dropped to 0.5°C.  Part of image - 60s exposure, gain of 50.  Here comes the cloud...

Camera temperature has now dropped to -0.2°C.  Part of image - 60s exposure, gain of 50.  The clouds have gone.

This ASI 120MC-S camera seems to be more sensitive than the ASI 185MC though I guess it's difficult to tell with the moon in the image.  There another difference too - when the 185 was imaging the sensor temperature increased whereas with this one it doesn't.  The 185 had a separate image sensor PCB whereas this has the sensor mounted directly on the main PCB.

I guess I should stop imaging and get on with the construction...

51 minutes ago, Gina said:

Darks are a problem as the lens doesn't have a shutter or aperture control.

Can you not cap it?

The historic choice was un chapeau ?

I guess I could cover the whole dome and take a dark.

This needs work before I can do any more testing.  The focus I set up manually needs setting up again and it's very critical - a few degrees rotation makes a difference, so I need the motor focuser working.  I also need to arrange to clamp the camera onto the Peltier TEC.  Then there's the outer casing and dome to sort out, with the problem of sealing.  I've been concentrating on my observatory today.

Here's a screenshot of the FITS image - out of focus!  30s and gain at 50.  Camera temperature 1.2°C no cooling.  Too tired tonight to do much but may do more to it tomorrow though whilst the weather is good I want to do the observatory.

The observatory jobs are on hold today - weather not good enough for roof repairs and waiting for parts for the roof automation - so this project may get some attention today, if I can get my brain to engage! ?