Gina

This is an option.

Dome added to assembly. This shows that the dome is quite close to the camera housing extension that accommodates the USB plug but may be alright - just. There is also the question of the remote focus gears still to be worked out (unless I go for preset focus). On top of all that I have to sort out how the camera housing id going to be fastened together and to the base part.

Decided to get the latest version.

I might do one day but I've got too much on my plate at present.

Cooler made visible and all plastic clear blue.

Gradually working through the design of the various parts and fitting them together. Here is the assembly as far as I've got. Camera housing is shown in clear blue, camera, lens and cooler housing in solid white and the fan and heatsink/cooler are not visible.

Good luck. I totally respect those who grind their own mirrors.

The TEC1 12703 Peltier TEC has arrived and I am testing it. I have the current thermal jacket on the camera though this will be changed. Running off my standard supply of 13.8v. Camera temperature started at 33°C and has gone down to just 5°C, a drop of 28°C. I don't think that's too bad for single stage cooling with just air cooling. TEC is drawing just over 3A.

Think I might the second edition from Amazon Prime. Should have up-to-date info I guess.

I see your "Inside PixInsight" is a Second Edition. I'm wondering what has changed from the first edition I have.

This shows the inside of the roof with the damp-proof membrane pulled down a bit to show the boards. There is already a gap of about an inch with rubber roofing overlap that provides ventilation.

It took me a while to work out how to open the box when I first bought Baader filters a few years ago, so you're not alone and I bet there are others too!

The ASC can go on the south side of the ROR at the apex with a hole in the shiplap just to one side of the internal frame members. This was what I did once before with an earlier version but with just wires going through the shiplap boarding as can be seen in the second photo of the inside of the roof.

This is a more likely shape for the bottom part.

CCTV cameras are not usually sensitive enough to show stars. As a comparison, I'm using an astro camera and 60s exposures. CCTV cameras are limited to 1/25th second or maybe 1/50th. PAL TV standard uses two interlaced frames of 1/50th second each.

Wouldn't cover the whole sky though.

Here's a rough cross-section of the ASC. The left hand tubular section goes into the observatory to draw in dry air. The fan blows the air through the fins of the heatsink and out the sides, then up towards the dome and out of a ring of holes just below the dome. A 3D printed housing surrounds the camera to provide thermal insulation and a sealed enclosure. Some silica gel desiccant bags will go inside the camera enclosure to dry the air and prevent condensation in the camera.

I have another idea. Two enclosures (sort of). An inner enclosure just containing the camera with a seal around the bottom of the lens and around the Peltier TEC(s) with the USB cable and TEC wires sealed. This would have desiccant bags to dry the air in the camera. Then below the TEC would be a finned heatsink. Air would be blown through the fins and out at the sides up to the dome. An outer casing would enclose the whole assembly up to the dome with vents just below the dome to let the warm air out. The bottom of the outer casing would be extended to go through the side of the observatory roof. I'll draw a CAD model.

I'm not happy using a fan outdoors where it can get drenched with rain. Another idea would be to take pretty much dry air from the observatory and blow it out to the ASC but this is getting complicated again - maybe not quite as much as water cooling.

A couple of photos of the outside part of the large pulley cover.

Another thing I'm looking at is the mounting. Two possibilities here. The aluminium pipe attached to the north side of the observatory or attached to the apex of the roll-off-roof. The former favours a cylindrical ASC housing and the latter is suitable for a rectangular box shape. The large passive cooler favours the box shape - it is not easily mounted atop a round mast. Actually, the passive cooler doesn't work too well with the cooling face horizontal - I think it was designed to have the face vertical so that air could easily rise between the vertical fins by convection. I've just tried it with a Peltier TEC and the camera. The camera temperature started at 25°C dropped to 6°C then rose to 12.5°C as the cooler heated up until it was almost too hot to touch! Think it needs a fan.

Been looking through my earlier ASC threads. The new Fujinon lens is definitely poor at the edge of field so I think I'll stick with the Arecont type. Still feel sick at smashing the first Fujinon lens! The front lens element has never shown up! Might use the Fujinon for a daytime ASC if I bother. The ASI178MC is now not doing anything but OTOH it might be useful for planetary imaging.

Been thinking about getting the heat from the cooling hot side up to the dome for dew heating. One possibility is an aluminium tube from the 100mm square passive cooler/heatsink up to the dome. Another is an internal finned heatsink and small fan. The aluminium tube idea is simpler so I've ordered a 4" OD x 100mm x 1.5mm thick tube from ebay with 1st class post delivery. This will also increase the heat radiating area on the outside to improve cooling. This tube is too long for use with the smaller lens but I think would be about right with the Fujinon. There is no focussing facility on the Fujinon lens but I might try fixed focus using shims with "trial and error" manual focus. A further simplification. Alternatively, I could shorten the tube in my lathe.

Regarding the camera cooling, I've been using a 30mm square 19W Peltier TEC but the camera base will take a 40mm one quite easily and I think this size may work better. I've ordered a TEC1-12703 module to try. Probably not as efficient as the £30 ones from Farnell Element14 etc. I may go for dual stage cooling with air cooling of the hot side. I've decided water cooling is too complicated. With air cooling, the hot side will be running much warmer than with water cooling which held the hot side just a degree or two above ambient. This means I can use some of the heat from the warm side for dew heating.