Gina

Here is a screenshot of the camera image. This is my living room ceiling and walls. This is an exposure of 0.1s. One thing is clear - the image from the lens is not central on the sensor and I'm losing some view at the top. Maybe I can print an offset adapter to correct this. The error appears to be about 0.5mm.

Good.

Time doesn't cost me money though admittedly I don't know just how much of it I have. I could have saved time instead of money if I had used the ASI 183MC-PRO USB 3.0 Cooled Colour Camera at over £800 - the cheapest cooled astro camera that FLO sell AFAIK. That would have saved all the cooling problems. Of course I would have had to arrange that I got its cooling air from inside the observatory but at one stage I had a design for that.

It does come at a cost unfortunately.

BBC4 at 10pm tonight. In just over an hour.

I want to get the ASC finished and installed ASAP so I'm putting up with the less than pleasant appearance. One day I hope to produce a nicer looking case that is airtight and partly transparent to show the state of the desiccant. If I could find a humidity sensor that went down low enough I wouldn't need to see the desiccant.

Circuit Diagrams :- Cooling :- The Peltier TEC is run continuously on a low level at about 5v to stop the camera overheating in the thermal insulation. For night viewing, the TEC is run from the full supply of 13.8v switched by a GPIO pin on the RPi. The J438 P-channel MOSFET is turned on via the EL8217 opto-coupler providing the full supply voltage to the TEC. Dew Heater control :- In this case the dew heater is connected directly to the main supply and the return is switched by an N-channel MOSFET (IRLZ44N) to control it. Again the power circuits are isolated from the delicate RPi data side with an opto-isolator.

I can protect the cap with aluminium foil to keep the UV off it. Also, the case of the ASC will shield it from direct sunlight. I think I may also glue aluminium foil onto the ASC case to reflect UV.

Yes, it's a full screw-on cap rather than part twist. I was looking at a glass jar with metal part twist cap at first but thought it wasn't very secure. The mustard jar is smaller too.

I'm looking at a Colman's Mustard jar about 3" high and 2" OD at the widest part at the bottom.

I'm keeping this thread going to consider ideas for improvements - the Blog will be for pretty much the final design. I'm satisfied that the design is fine except for the possibility of the case leaking and damp (or worse) getting in. This has always been a concern with cooling the camera below freezing to reduce image noise. Ingress of moisture can cause two problems - condensation on optical surfaces or worse, ice melting during daytime and the water damaging the electronics. I shall be using "indicating desiccant" where the colour changes from orange to dark green if it gets exhausted but apart from the top, the case is opaque ABS. I looked for a transparent box but no joy. It would be helpful if I could see the desiccant and know that the ASC insides were dry. I've been thinking of how I could make the desiccant visible. Now to my latest thought... How about a small glass jar with a lid that seals, with the lid glued and screwed to the bottom of the box and a hole through the lid and box to allow damp (or even water) to drain into the jar? The jar would contain a sachet or two of desiccant and any colour change would be clear. Also, if the desiccant became exhausted after time it could be replaced easily.

I have started a Blog for this latest version of my ASC HERE with a parts list.

PARTS LIST :- Camera :- ZWO ASI 178MC USB 3.0 Colour Camera Lens :- All Sky Lens for QHY5-II and 1/2 Inch Camera Dome :- 3.5" Clear Acrylic CCTV Dome Case :- 3D Printed Case Sealant :- Gorilla Versatile Mould-Resistant Sealant, Clear Desiccant :- Dry & Dry 10 Gram [25 Packets] Premium Silica Gel Orange Indicating(Orange to Dark Green) Silica Gel Packets Desiccant Dew Heater :- Dew Heater Module - All Sky Camera Peltier TEC :- Peltier Module, 54.6W, 4.4A, 20V, 40 x 40mm Waterblock :- CPU Water Cooling Block, Waterblock Liquid Cooler 50mm Copper Base for Intel/AMD Coolant :- XSPC XS-EC6-CL Non Conductive Coolant - Clear Radiator :- BQLZR 80 Row PC CPU CO2 Water Cool System Heat Exchanger Radiator Fan :- Coolink SWiF2-800 Fan 80 x 80 x 25 cm Water Pump :- Decdeal Mini Brushless Water Pump DC12V 5W Ultra-quiet Waterproof Submersible Fountain Aquarium Circulating 280L/H Lift 300cm Computer :- Raspberry Pi 3 Model B+ MicroSD card :- SanDisk Ultra 16GB microSDHC Memory Card + SD Adapter with A1 App Performance up to 98MB/s, Class 10, U1 HAT :- DIY Proto HAT Shield for Raspberry Pi 3 and Raspberry Pi 2 Model B/B+ / A+ KB 5v PSU :- LM2596 DC to DC Buck Converter 3.0-40V to 1.5-35V Power Supply Step Down Module

I think I have the design for my latest ASC pretty much finalised now so I'm starting a Blog for it.

Checked my account with rs-online.com and found it. Ordered October last year.

Can't find the exact part number for the Peltier TEC but I see I bought it from RS-online and it's about 15v and 40mm x 40mm drawing about 3A at 13.8v.

I'll have to check - the info should be in this thread (somewhere).

Picture please.

Not for me but even though an OAP, still learning. 😀

Though I'd lost the Peltier TEC I was going to use but have found it. (I do have a smaller one in reserve but won't need that now.) Just tested it by attaching it to a large heatsink with thermal grease and applying power. Checked first with 5v then increased it. With 10v applied for a while the cold side settled down to -8°C with the heatsink at 22°C. It was quite happy with 13.8v applied, drawing 2.5A and reducing as the cold side got colder. As an experiment I tried a TEC1 - 12706 cheapo. It took 4.5A and got hot both sides on 10v. The thermal heating exceeded the Peltier cooling. OK so the so called "cold" side wasn't as hot but...

I have this odd feeling that tomorrow might be called Saturday but could be wrong - nothing is certain these days. Well, maybe one thing, we aren't getting any younger. Just more confused.

Oh no you're right - it's Monday!

Are you sure it's not Wednesday???

Mine could do with a coat of wood preserver - 10 year service 🤣

The older you get the faster the time goes. Seems only yesterday it was Friday last week!! That tells you something! 🤣