All Sky Camera Revisited

[Gina]

May change the focus lever slightly to make it easier to print.

Edited September 11, 2020 by Gina

[Gina]

Attachment for light extension spring,

[Gina]

This is the ASC as it will fit on the pipe/mast.  It's big - about a foot high overall and up to 8" diameter.  It includes remote focussing and lots of space for the electronics.  I haven't sorted out the dome cover yet.  May be able to do that tomorrow.  I'm thinking the mast cover motor may go in the other side opposite the focus motor.

Edited September 11, 2020 by Gina

[Gina]

Started designing the cover.

[Gina]

The biggest problem is driving the cover without risking wet getting inside the ASC casing yet have the motor protected from damp.  Either that or some method of opening and closing the cover that will stand getting wet or at least damp.

This is where the SGL membership with the vast range of experience might help.  Any ideas very welcome, please.

Edited September 12, 2020 by Gina

[DaveL59]

perhaps also consider the effect of wind as it'll act as a sail and could lead to other damage or vibration.

In terms of operating, an external cam-lever could crank the cover while the motor remains inside the body, with o-ring seals to prevent water ingress to the housing? Much as windscreen wipers operate, tho you'd need to maintain the pivot points to keep them cleaned and greased. Getting the dome to flip far enough for it and the crank/lever to be below the camera horizon and still be able to return back to park could be a challenge tho. Thinking about it, if you flip that cover so it's an inverted dome, any rain would collect in the bowl which would add to the problems, as well as dousing the main casing when trying to close. Would test the water sealing for sure.

I wonder if a split clam-shell type would work, overlap where they meet for UV protection. Wind would still be an issue tho but perhaps less in terms of being a water catcher.

[Gina]

My first thought was to feed a shaft through a gland for sealing - this does seem the simplest solution.  I have a box of small O rings.

At first it seems simple enough to make a remote controlled cover but when you look into all the details, it isn't.

1. The cover must not obscure any part of the all-sky view so all of it must be below the top of the lens
2. It must not collect rainwater.  Even though it will only be opened in good weather, rain can come suddenly.
3. The drive mechanism must not be subject to corrosion
4. It must be robust enough to withstand storms

[Gina]

This shows the sort of problem.

[DaveL59]

7 minutes ago, Gina said:

My first thought was to feed a shaft through a gland for sealing - this does seem the simplest solution.  I have a box of small O rings.

At first it seems simple enough to make a remote controlled cover but when you look into all the details, it isn't.

1. The cover must not obscure any part of the all-sky view so all of it must be below the top of the lens
2. It must not collect rainwater.  Even though it will only be opened in good weather, rain can come suddenly.
3. The drive mechanism must not be subject to corrosion
4. It must be robust enough to withstand storms

yep, was thinking that when you first suggested doing this. A simple 2-lever affair may do the job and if you get the lengths correct you should be able to achieve an open/close rig, though you may need to gear the 2 levers where they operate against each other so they don't invert, as it were and then the dome doesn't move at all. Tho a stop at the dome joint would prevent that perhaps which may be simpler. Don't forget to factor for the gearing etc too, more complications.

Something like this but with more smarts to handle how far you rotate each way, microswitch limiters in the internal gearing may suffice as used with sunroof motors in cars perhaps.

 

[Gina]

This solves the rainwater problem but...

[Gina]

And closed also showing the axle.  That mounting axle is all of 100mm (4") out from the edge of the cover.

[DaveL59]

cranking that could be fun but a good solution to the water cup issue 🙂 

[Gina]

There's another thing to add to the list - must be capable of being 3D printed (without support).

[Gina]

I've changed the cover design to ease the rainwater problem.

 

Edited September 12, 2020 by Gina

[Gina]

Tried your suggestion of cranking the cover to axle part which does help with the angle but too much intrudes on the FoV!

[DaveL59]

24 minutes ago, Gina said:

Tried your suggestion of cranking the cover to axle part which does help with the angle but too much intrudes on the FoV!

all I was more referring to the 2-lever arrangement to move it but it would need an attachment point somewhere on the dome or the extended bracket to act against. I was thinking along the lines of a longer arm attaching to the side of the cover than at the hinge.

[Gina]

I'm not sure what you mean by a 2 lever arrangement but one thing is sure - what I have won't do - there's nowhere to put a drive gear or pulley that wouldn't be in the FoV!!

[Gina]

Think I'm nearly there- watch this space.

[Gina]

Offset bracket and drive wheel (probably a 3D printed spur gear).  It's very close to shedding rainwater in the open position and I may be able to make the main casing shorter depending on how well the electrons fits in.

[DaveL59]

could work. I was thinking along the lines of...

but I've not done the math but in theory with the right length levers the rotation may be good to push the dome beyond the vertical and continuing rotation would then being it back down to the parked open. Would need to also be able to work in reverse of course. The geared wheel arrangement you've drawn would work too of course and with a worm gear it'd stay locked in position well so may be simpler to build.

[Gina]

I'm doing a test print to see how all the electronics fits in and it's looking like I shall be able to reduce the height considerably.

[Gina]

It would seem that there's plenty of room for the RPi 3 plus HAT to sit flat inside the casing and I reckon I may be able to halve the space required which would result in this.

[Gina]

Been searching for brass worms and worm gears without much success other than on a slow boat from China and not quite what I want anyway.  OK I can 3D print a pair but this is not ideal - I would prefer metal (other than ordinary steel).

[DaveL59]

perhaps this seller can make one to your spec?
https://www.ebay.co.uk/itm/BRASS-WORM-AND-ALUMINIUM-WORMWHEEL-50-TO-1-RATIO-1-PAIR-PER-PACK/162175321334?hash=item25c26704f6:g:qikAAOSwU-pXuH7j

 

[skybadger]

 Hpc, stock gear, sdp, duval, should all stock standard sizes.