Gina

Thank you Mike - that's very interesting. Maybe I'll have another go.

Thinking about the enclosure/casing/container/etc... 3D printed seems to be porous unfortunately which is a big disappointment! An empty paint tin of a litre or so might be a possibility - that would definitely be waterproof. If I don't put the RPi inside I can use metal.

Overall I think I would prefer the RPi etc. where I can get at it easily - ie. inside the observatory. This fits in with making the ASC as compact as possible and reducing the volume of air to keep dry to avoid condensation inside the camera and lens. OTOH it also means I shall need waterproof connectors (or cables though grommets for sealing) for USB, power to Peltier TEC and focus motor plus possibly dew heater (to heat dome and stop dew on the outside). If I were to use a dual stage cooler, the hot side could be well above dew point, maybe even above ambient temperature if I used air cooling and would eliminate the need for a dew heater. Of course, with the RPi etc. in the ASC, only the 12v power wires need to pierce the casing. Comms to/from the control computer would be WiFi. Apart from the access problem this means the RPi may need some sort of cooling whereas in the observatory there can be plenty of air cooling.

As a change from the high power image processing in PI I've come back here and just looked through this thread. I'm thinking I'm setting myself too much of a task trying to get high sensitivity out of a colour camera. Also, whether it's the camera or the software/firmware, I sometimes get strange colours. This, plus the reply above leads me to use the ASI178MM camera. I've concluded that sensitivity is more important than colour for night sky. The fact that I have put this project aside for so long indicates my dislike of the current setup. I don't like the rectangular box - OK I know the look of the thing may be less important than the functionality but those are my feelings. The water cooling is very efficient but I don't like those flexible tubes coming out the side - very untidy. I have waterblocks with the pipes coming out the bottom which may be better. The tubes are larger than necessary too but that's easily fixed. OTOH water cooling uses a lot of parts. If I use a mono camera it may not be necessary to get the camera as cold as with the colour one. ATM I'm using a single stage cooler - manufacturers of cooled astro cameras use double stage cooling and air-cool the hot side. I could do the same if needed. I'm using an f2 lens so there's quite a good amount of light available. Cooled astro cameras as designed for use with telescopes where the aperture is more like f5 or more. Countering that is that DSO imaging uses stacking which I'm not using in the ASC so need single subs to be good. Yet again, I'm dealing with stars rather than glowing clouds of gas and also wideband imaging so capturing more light.

As a result of reading another thread about binning colour images I've been thinking about my ASC. Currently I'm using a colour camera (ASI178MC) but if focus and lens resolution are very good, each star is likely to fall on just one pixel so star colour will depend on which colour pixel the star lands on and my intention of using a colour camera to show star colour is thwarted! Moreover, sensitivity is going to be much reduced compared with the same image sensor in mono form (ASI178MM which I also have). I was considering binning to increase sensitivity but it all depends on how good focus and lens resolution is. My thought is - should I change to the mono camera for nighttime imaging? I should see more stars but the result will not be as "pretty". I could use a separate ASC for daytime with reduced requirements.

You can set compensation for backlash in some drivers.

Here are screenshots of the CAD models of the back and front of the large pulley cover. About half the cover is outside the observatory when the roof is closed. The photo shows the old green cover - I have yet to photo the new one.

There's only one wire for the direction. All of 10mm long.

Another fine spell has enabled me to connect the drive chain parts with a new link, thread it through the gap between large pulley and casing, through the motor unit, round the small pulley and hook up onto the spring and tension adjuster. Then tighten the tensioner eyebolt. Chain drive now ready for using the motor - chain runs very smoothly. So next job is the programming then I can install all the parts in the box and attach it to the wall.

Yes, that's what I thought but can't find one. The direction going o/c would not affect both directions. Weird. Might try resoldering the driver connections though.

I don't know. All I know is that when I operate the focussing control from the control panel on my main PC the motor turns the right way mostly but sometimes the wrong way. The direction is controlled by a data input to the A4988 driver module. Logic "0" makes the motor go one way and logic "1" the other as I expect you know having used these or similar drivers in 3D printers. The only way I can see that this could happen would be if the signal from the RPi was between the logic "0" level of <0.8v and the logic "1" of >2v. My DMM shows voltages of 0.5v and 3.3v on the Direction pin depending on the set direction. If the problem was a dry joint I would not expect the 3.3v state to give the problem as the o/c state of the A4988 is logic 1 I believe.

Been fault-finding the focus motor drive. Replaced the A4988 driver module and now the motor rotates but the direction is unpredictable. More testing needed.

The print of the front in blue PLA came out fine - virtually perfect. A gap in the rain enabled me to get out to the observatory and try the new cover parts. They fit perfectly

Seems I was using the ZWO camera and PI in my earlier imaging and getting fairly good results so I now need to get back into it all. Ah the sun's come out - shades of "Hello mother, hello father" 🤣 Here's a copy of a post a couple of years ago. Seems I had pretty much got to grips with PI then...

Having problems with a loose Precision Piezo module in the E3D extruder when hot at present but that's another matter! I hate 3D printers at times but can't manage without!!

I wouldn't have thought 4% was a significant error in extruding. I fiddle with my extrusion rate during printing (in Duet) by as much as several tens of percent! Maybe I'll get things right one day!!! 🤣

My exposures are unlikely to be over 2m maybe 5m for dimmer DSOs. The lower read noise permits shorter exposures at higher gain I shall need to experiment to find the best balance between full well capability and gain/sensitivity. For my very wide angle images I have been using 60dB gain (the maximum) but may find longer exposures and lower gain give more image depth. At least the high sensitivity of the ASI makes focussing and plate solving easier/quicker. Yes, lots of experimenting and practice needed to get the best out of the camera and the new software, though I did use PixInsight before, it was some time ago and I need to get back into it. Still learning KStars/Ekos/INDI. I like the control the Open Source INDI drivers give me - I can change them to control practically everything. I think the problem I'm having with distrusting my decisions is probably all due to this terrible weather and not being able to actually capture images! Thank you for your encouraging comments

Thank you everyone - very interesting. More thoughts on this most welcome. It's certainly true that I need to get "up to speed" again both due to not imaging for some time and the new hardware and software. I think my mount is not only good kit but well set up too and the shorter exposures mean I can get away without guiding for a lot of my imaging, which simplifies matters.

I know this has been discussed before but a new thread seems appropriate for my particular situation. Looking at my imaging results from years ago, it seems I was getting better results than more recently. Now there may be several reasons for this including age but I'm wondering now if I did right in selling my Atik 460EX mono CCD cameras and buying ZWO ASI1600MM-Cool instead. The FLO website shows the Atik cameras being a lot more expensive that the ZWO and I have always had the feeling that you get what you pay for but guess this is not always so. I can't remember now what my reasons were for doing this as I sold used and bought new. I am now wondering if I did the right thing. Maybe I should have kept one 460EX particularly for the smaller DSOs but I could have needed the money. I would appreciate your thoughts on this. TIA.

Tried all sorts to get white PLA to print properly but no joy. Changed to blue and printing fine!! Go figure. 3D printers are as much black magic as computers!!

Eventually printed the back after tweaking my printer but found I'd printed the front wrongly - used mirror instead of rotate 180° so came out back-to-front - DOH!!

Now using a different design with a two part cover so that I can print it flat rather than on edge. Printed the front which went fine and now the back.

Left the print running overnight but this morning found the print had failed near the top!

Printing the new large pulley cover. Here are screenshots of the CAD model and the arrangement for printing in Slic3r. The Cad model shows the true orientation in use.

These are the Arduino inputs :- OPEN - Push button CLOSE - Push button STOP - Push button Rain Sensor (relay) OPEN limit switch CLOSED limit switch RPi Open RPi Close RPi Stop Motor current I think I should include a timer too, to turn off the motor if the appropriate limit switch is not activated in a reasonable time. This would also signal a Fault to the RPi, same as the motor drawing too much current. The cause could be a broken drive chain or connection.