DIY all-sky cam?

[Gina]

The teeth turned out to be rather small for accurate printing so I've increased the size.

Adjusted to fit in the space available as shown by the grey circles and outline of solenoid.  The inner circle shows the radius of the shutter axle hole.

[Gina]

I thought I would have to mount that solenoid vertically or make the casing bigger but it seems it will just fit in

[Horwig]

I have a shutter that works, the meter movement is araldited to the edge of the pcb, and it all fits the existing casing. need to sort out the anti dew, then it might all work

H

[Davey-T]

Hi Gina, I think your dad and mine would have got on well with each other, my dad made a coil winding machine to make coils for an electric organ and I had the job of winding them, hand powered but at least it had a turn counter

My wife used to make lace and had a bobbin winder which looked very similar.

I've lost track of why we need a shutter, I accidentally left a web cam on one scope while imaging the Sun with another scope, doesn't seem to have done it any harm but it wasn't recording, would that make a difference ?

Dave

[Gina]

I have a shutter that works, the meter movement is araldited to the edge of the pcb, and it all fits the existing casing. need to sort out the anti dew, then it might all work

H

Great

The meter I bought has a similar movement but I would need to redesign many of the case parts to do the same.

I'll certainly look forward to seeing your results

[Macavity]

Useful thread -- Though I'm working more on electro-finders for remote Video.

But, having learned that the thread size is 12mm 0.5mm - Dubbed S-thread(!!),

I now find there are 50mm F2 lenses to fit my 0.003 lux generic Ex-view cams. 

http://www.cameras-cctv.com/mini-cam (sadly no more 0.003 lux'ers at the mo) 

http://stores.ebay.co.uk/Stock-Optics-Ltd (Lenses + other interesting bits & bobs)

IIRC, I get a typical limiting magnitude +8 through my standard D=50mm finder.

But the field was a bit limited (f=150mm finder = <~2 deg with typical 1/3" chip)

I can now extend this to a more useful (c.f. visual) 5-6 deg for remote pointing.  

Might even get around to an All Sky Cam one day, so keep up the good work... 

[Gina]

The muscle wire has just arrived   Now the fun can begin

[Gina]

Tkaen them out of their little polythene packets.  I got two thicknesses - 0.005" and 0.012" with working currents of 200mA and 1.5A.  The thinner one needs a magnifying glass to see it   Looks about the thickness of a human hair   Might work in shortening mode but I think would be too weak otherwise but we'll see.  The thicker wire seems more reasonable   I'm taking a rest to let my eyes recover and have a think

[Gina]

The wires were formed into a short loop then the end wound round the middle a number of times.  The fine wire took a lot of unravelling under my illuminated 3x desk magnifier - the other wire was easier.  The 0.012" wire dropped just over 5v @ 1.5A for the provided length of 1 foot.  The 0.005" wire of the same length, about 4v at 200mA but it didnt seem to get properly hot so I upped the current to 300mA and then the wire straightened out.  At this current it dropped about 6v for the full length (a foot).  I checked the contraction of the fine wire and got about 2mm or so in 30mm ie. about 6 or 7%.

I'm thinking now about how best to use the muscle wire. 

One idea would be to put the motor back on to use as axle and bearings, use a torsion spring as before and wind the muscle wire into a spiral so that when straightening out would turn the shutter against the spring.  Since the wire is bare I think I'd need to thread it through sleeving.

OTOH it might be easier to use a 3mm SS axle and put the works outside the dark chamber.  I might find a proper use for the tiny DC motor   Maybe I'll make up a test rig.  I think I'd rather work in a less confined area than the dark chamber (casing that separates the QHY5 PCB from the lens).

[Gina]

Made the test rig and been trying it out with the thicker muscle wire.  Unwinding coil version.  So far not very successful But I guess it's early days - I've never played with this stuff before

A couple of turns of the thicker muscle wire

A light return spring

As above but with current on - just a small movement of the pointer

More turns to see if I can get more movement

Current off

Current on but but only very slightly better

[Gina]

Looks like that method is a no go

I think it's going to be something based on the straightforward contraction in length.  Or maybe the solenoid is simpler after all

[Gina]

I did some calculations.  If I were to use the full length of muscle wire I would get about 2mm of contraction.  If that were to be fed to the shutter axle with thread we would want a 6mm diameter bobbin to give 40 degrees of rotation for the shutter blade.  It could have a 30mm rod or tube extending down into the support pipe and the thread passed over a pulley to pull horizintally.  (Or it could have a 30mm pipe extending out the side )  Alternatively it could use 15mm of wire and the thread wrapped round the 3mm axle.  I think the axle would want something better than plain plastic bearings though to reduce friction.  Overall I think the solenoid would provide a neater solution.

[Gina]

I've given up on the muscle wire - too difficult to use.  The solenoid seems to make more sense and I'm working on the structural parts to hold that and transfer the motion into rotation for the shutter blade.  It's not easy visualising how everything fits together even with 3D drawing software.  A lot of trial an error - I'm getting through rather a lot of filament with the various projevcts I'm working on.  Fortunately the 1.75mm ABS is a lot cheaper than the 3mm PLA I was using with the other machine - just over half the cost.  Also, I not losing filament on bad prints, just badly designed parts

[Gonzo]

Waiting here for a clear night (currently somewhere in Germany on holidays) to check the focus. Once done, I will seal the dome to the box.

[Gina]

Photos of the solenoid shutter control.  This is the solenoid in the frames with the lever.  Not yet connected to the shutter blade.  One photo shows the "pinion" though not very clearly.  ATM I've mislaid the 3mm rod for the axle

[JamesF]

That's all looking very neat, GIna

James

[Gonzo]

Well, it's a nice clear night with the Milky way on sight, however my rpi camera can't see much.

Not sure if it's a camera issue or the lens I'm using. I would have thought I could see more than back home, but... not much.

[Gonzo]

It appear that my request to longer exposures on the Raspberry camera has been answered, you can now do 6 seconds exposure (found out on the forum).

Which is more than enough for me.

[Gina]

That's all looking very neat, GIna

James

Thank you James

[Gina]

Think I've now finished the casing   Conical attachment to the mast (aluminium tube 1" OD) with notches and pegs to clip onto the 3 legs and the bottom plate.  No screws are used in the construction - just plastic parts that clip together or hold by friction.  An outer cylinder supports the plastic dome and further holds everything together.  One exception to this principle - the piece that moves the focus lever which is glued to the dome ring.  Oh and the lens screws into the plastic dark chamber

[ChrisLX200]

That looks very good Gina, and a darn sight easier than hacking one out of heavy alloy tube   The plastic will not lose heat as quickly (and retain heat) so hopefully less of an issue with dewing up. Not sure about the colour choice though...

ChrisH

[Gina]

That looks very good Gina, and a darn sight easier than hacking one out of heavy alloy tube   The plastic will not lose heat as quickly (and retain heat) so hopefully less of an issue with dewing up. Not sure about the colour choice though...

ChrisH

Thank you Chris

I could reprint the exterior in another colour if you like   I have a fair selection   Some colours seem to print better than others.  The fluorescent green prints perfectly as does the clear/transparent.  Red and yellow are also good.  I've tried two different suppliers of black and one produced very good prints and the other, not so good.  Dark green is poorish and dark blue quite bad - the light blue is fine.  The white filament I have is poor.  I also have orange, pink and purple that I haven't tried yet.

The last colour I used on this project was the light blue which matches the sky (sometimes) and seemed appropriate for an all-sky camera but it did seem to rather clash with the dark green shed - er. obsy.

So there you have it   Which colour would you favour?  As a matter of interest

[JamesF]

Dayglo pink.  It's the only option

James

[ChrisLX200]

I think I'd go for black myself

ChrisH

[Gina]

Hmmm...  Black has the advantage of blocking the ingress of light better than any other colour, though light can still get in downwards between the dark chamber part and the dome rim (unless I put a black baffle in the gap).  Then it can get reflected up and through the QHY5 PCB which isn't opaque, I've discovered, and lets light through which can be seen in daylight mode   I was wondering where this "fogging" was coming from.  I was thinking of sticking some flocking material around the image sensor to stop this.