Gina

DC 12V 1A 10mm Stroke 15N Force Open Frame Type Solenoid for Electric Door Lock This would seem to be just the job. On roof closing it would slide back on its spring and lock the roof shut but see the quote below.

That was what I had in mind but if the wind has been blowing on the roof the latch will be pressing on the bolt so it will need a fair force to pull it back. This was mentioned in some of the comments/reviews. Apparently, a bolt that was quoted at 15N force (1.5Kg) only had this force when bolt pulled back ie. holding force, and wouldn't release a door which was arranged to spring open when the solenoid was operated.

Can't find anything that will pull back a bolt or latch when there's a force against it. I'm going to have to think about this. Two ideas come to mind - screw operated with a motor a la linear actuator or a multi-lever system that is set by closing the roof and can be released with a small force.

The larger silica gel bags have arrived.

Yes, that's right, it a pull type that I want but that little 6v solenoid would have far too little pull force. I'll do a search...

Ah yes, solenoids, that's a different matter. I was looking at linear actuators which are motors and screw shafts. I was doubtful if solenoids would be powerful enough. I would want it to lock with no power and unlock when power applied. I wouldn't want to use power all the time the observatory was out of use. ie. the "failsafe" mode wants to be "locked". Have you used the solenoids you've linked to and would they be powerful enough? I prefer to over-engineer rather than under-engineer.

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.

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.

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.

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

As can be seen in the DIY Observatories forum, I have some work to do on the observatory though it is usable.

Thank you Alex ? I've decided to start a new thread about it now and let you have your thread back.

I shall start a new thread when I get to doing repairs. Meanwhile, the rain stopped this afternoon and the sun popped out for a while, gone in again now though. Probably getting ready for the next batch of rain... I was able to pop out to the observatory and have another look. The plywood has pretty much disintegrated in a small area and the rubber is wet underneath - I was able to pull down an area several inches wide and a couple of feet long. Looking on top I can't yet see where the wet is getting in but it's more than wicking - there was wet on the floor in that corner, though not much, so it's not a big leak considering all the rain we've had lately. I could see that the rubber is no longer glued to the plywood all over. I shall have to have the barge board off that quarter and the batten off the end of the roof above the guttering so that I can fold the rubber back and see what I can see. That will need reasonable weather but at least the forecast is better for next week.

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.

Does it? I haven't found that with mine (and I have two).

I was thinking that if I fill the space between camera and it's casing with plastic foam there will be no room for extra air and no need for silica gel pack to dry it but then thought of the air in the camera, so silica gel is a good idea after all... Of course, the 3D printed camera casing provides thermal insulation as it's filled with lots of mini air pockets. Maybe a fairly close fitting casing with some space for a silica gel pack. I've closely examined the camera and there's definitely gaps round the connectors and I can see the PCB inside so the casing is not sealed in any way and there will be air inside the camera with a moisture content. This will probably condense onto the inside of the casing when it's cooled and heat given off by components may keep the electronics dry but I don't think I'll depend on it. The place where the USB plugs in seems a good place for the silica gel pack.

Focus motor bracket printed and installed together with stepper motor - now wants a pinion designed and printed. Electronics box also attached to dovetail bar - just needs a lid now.

With the rainfall lately I think the whole of SW England or more...

Thinking I might use the DHT22 temperature and humidity sensor to monitor temperature and humidity in the ASC I did a search to see if there was an INDI driver. Couldn't find one as such but did find a complete weather station in INDI called MeteoStation which I might take a good look at when I get back to my weather station project. Also, Indiduino ; An automation solution for astronomical observatories

Oh dear, I seem to have hi-jacked your thread Yawning Angel - sorry about that ?

Yes, I think the wet has been getting in for some time. The ply is soft and soggy but still seeming to support the EPDM (or maybe vice versa!!). I reckon at least a part of that sheet of ply will need replacing. To replace the full sheet would be a huge job and not practical IMO. It will be a patching up job. As if I hadn't got enough to do!!

Here's a photo of the camera and lens sitting on top of the Peltier TEC on top of the passive cooler, I'm now thinking about the design of the camera housing (with thermal insulation) and the outer casing together with how to seal everything against moisture ingress. I'm wondering if I can seal the inner, camera housing as well as the outer casing. I would feel happier with two layers of wet protection for the camera, in view of the previous catastrophe. Also, I'm wondering if I can arrange that warmth from the cooler can be arranged to rise into the dome to help with keeping dew off the outside. Both inner and outer voids will have silica gel packs.

Not sure yet. When we get a break in the weather I hoping to get out and have a better look. The EPDM looks intact from an examination yesterday but with showers and strong wind it wasn't practical to lift the EPDM and look underneath. Couldn't see anything wrong on top. Also, there was no sign of wet on the floor so it may be that water wicked up the plywood from the edge by the guttering. Gale force wind and heavy rain today.

Yes, that's what I'm thinking.

And I've been thinking about the storm locking. When the roof is motorised the motor drive would hold the roof closed and if the roof engaged pins and eyes or similar it should be pretty safe. Though I think I would be happier with something rather stronger to stop the roof being blown back by an easterly storm.