Gina

Imaging Saturn complete with rings with my first telescope and a webcam. Never to be forgotten.

More done to the design. Dew heater and remote focussing seem practical.

8 resistors for the dew heater and part of focus lever added.

Regarding cooling the Peltier TEC hot side, I currently see three options. Large aluminium cooler with forced airflow Large aluminium cooler passive Nofan It would save work without forced airflow. Nofan seems best but costs money. Still considering but favouring 2. or 3. Whichever cooler I use, I need to make space for dew heater resistors (unless I vent warm air from the cooler up to the dome, which I've pretty much rejected). It would also be nice if I could include remote focussing. Here is the current assembly without cooler. I think dew heater can go around the bottom inside of the dome. That may still leave room for a focus lever. I'll add to the drawing...

PETG uses lower temperatures than ABS and doesn't produce the noxious fumes that ABS does in printing.

Definitely!

WOW Wim, what a difference! Just shows that PI is very powerful and that I've got a huge amount to learn. Wonderful. Amazing first NB and goes to show what image processing can do.

Brilliant!!

On a previous version of my ASC I used the large passive cooler as exactly that - passive - just relying on convection of air over the fins. With the cooler horizontal this was not as efficient as it would be if the air was free to move straight up between the fins. But it was almost good enough. The results were given in the post dated 6th July. Seems to me that the NOFAN should work well in any orientation and with copper heat-pipes and large surface area it should be more efficient. I guess I could try the arrangement I used before though I would improve the mounting but the NOFAN would be much easier to mount. Must give it some thought.

Side view of ASC. It would be attacked to the side of the ROR with a bracket with the NOFAN well out in clear air.

The idea is to put this on the underneath of the Peltier TEC out in the open with free air movement over it. I'm thinking I might go back to standard dew heater rather than blown warm air. Seemed a good idea but now I'm not so sure.

This looks pretty amazing - I think it might actually work. NOFAN

A possible air duct. The large cooler fits in the top.

I could blow the air through like that or in the bottom and out the sides - more conventional and easier to arrange to attach to the ROR. I'm thinking maybe let the air flow out one side totally unobstructed but the other side part of the airflow ducted up to the dome. The result will be bigger printed parts but this is well within the 1ft (300mm) cube printing volume of my main 3D printer.

Thought I'd try using the large heatsink and 80mm fan as shown below. Better cooling even though the air coming out is warmer. Temperature started off at 28.5°C and went down to 7.5°C a drop of 21°C. That's a considerable improvement and not even using all the fan area. With that cooler and a decent TEC I should be in business!

Have you posted any details of your ASC design Jon? I would be very interested to see your ideas.

My camera body is 62mm diameter and 40mm x 40mm TEC diagonal is just under 57mm so fine. My airflow is from the observatory scope room which is very well ventillated - even more so when the roof is open but drier than totally outside. The air is blown from there with an 80mm fan (I also have bigger ones) up through the air duct to the heatsink - currently 60mm x 62mm x 40mm but I also have an aluminium heatsink about 100mm x 100mm x 60mm. I agree that closed cell foam is probably better than closed cell 3D printed thermal insulation, I may go for the foam. The bottom of the camera that's left after taking out the area of the TEC, will also be insulated. Since the camera temperature will be below dew-point I am enclosing it in a sealed enclosure containing a silica gel bag to dry the air inside. I think blowing all the warm air up and out at the top of the ASC may restrict the airflow too much. Using at least some of the warm air to blow onto the inside of the dome to stop condensation seems a good idea but I think I shall vent most of it straight out. I am now thinking about a major design change.

I've ordered that 40mm x 40mm Peltier TEC from RS-online. Should arrive Monday.

Tried 11v supply and a further small improvement. 11°C a drop of 18°C. Still 10°C wore than before. That's very interesting Jon. I have used RS-online TECs before and found them much better than the cheap ones. Guess I'm wasting my time with the TEC1 12703 and should "bite the bullet" and buy decent quality goods!

Reduced supply to 12v and got a small improvement. 12°C a drop of 17°C.

I don't know how I got this when I can't repeat it. A test result that cannot be repeated is not valid! With the latest test the current drawn is below 3A. Could the TEC have deteriorated, I wonder.

And another half degree to 15°C a drop of 14°C. I'm not impressed! Should be better in situ with cooler air to cool the hot side and a bigger fan.

Gone down another half degree.

16°C now. 13°C drop. Will see if it goes down any more but seems to have settled at that. Not as good as the previous result with this TEC. Wonder why....

19°C and still going down. 10°C drop.