DIY all-sky cam?

[Gina]

The all-sky camera with mounting brackets and ali tube on corner of observatory.  I may replace the bright green bracket with something less bright

[Gina]

The dome seems to scatter light a little and reduce contrast as a result, but I wouldn't say it was hideously bad at all.  A glass dome might be better, but I don't think I'd regard it as essential at this point.

James

I agree.  I noticed that on the laptop in the obsy but I also agree that it's not seriously bad.  I think the dome changes focus a little bit.  I've been thinking that remote focus would be good.  Uh oh, another Arduino   Or more precisely an ATMEGA chip.  Alternatively, focus control brought out to a knob on the outside as access to the focus lever is not possible with the dome on.

[Gina]

Sun almost gone.

[Gina]

I think one problem with the dome might be that somehow the lens has come higher up in the dome than I originally intended.  I can fix that

[JamesF]

The all-sky camera with mounting brackets and ali tube on corner of observatory.  I may replace the bright green bracket with something less bright

Bright is good.  Who wants to live in a dull world?  I'd stick with it

James

[JamesF]

I have been thinking (I know, steady on) that if an application is going to capture images at intervals then it might be sensible to be able to take several a few seconds apart in case there's a problem with one.  Does that make sense do you think, or is my paranoia getting the better of me?

James

[Gina]

I have been thinking (I know, steady on) that if an application is going to capture images at intervals then it might be sensible to be able to take several a few seconds apart in case there's a problem with one.  Does that make sense do you think, or is my paranoia getting the better of me?

James

Might be an idea   Another though would be to stack several frames to improve S/N ratio like we do with "normal" astrophotography

[JamesF]

Hmmm.  My initial inclination would be to leave that for a different application, but it might be nice if you were viewing the images as they were being captured.  Plenty there for me to think about, anyhow.  I need to do some research into alignment and stacking so it will have to wait for a while.  I'm trying to get my head around focus scoring at the moment.  How did I manage to do maths O-level, electronics O-level, maths AO-level, two maths A-levels (and physics too), more maths for my degree and never cover Fourier transforms?

James

[Gina]

Bright is good.  Who wants to live in a dull world?  I'd stick with it

James

Actually, I might go back to the corner I was originally going to use which the bright green bracket was designed for.  I need to arrange a new mounting and mast for my weather station away from where a scope would "look".  From the latest images it seems having the weather station mast quite near is not that much of a problem - it's about 2ft away ATM (mounted on a stout 4" square oak fence post). 

The weather station mast could go onto the middle obsy frame (the dividing wall between scope and warm rooms) and the all-sky camera on the NW corner of the warm room.

[ChrisLX200]

I've been working on mine too, using the QHY5L-II in the home-made casing (with dome and heater). This was taken just now and it may not look it but it's almost dark outside. I'm hoping there will be some gaps in the clouds, but at least I don't have to worry about a spot of rain...

ChrisH

[JamesF]

Looks very nice, Chris.  Colour works well during twilight I think.

James

[Gina]

Hmmm.  My initial inclination would be to leave that for a different application, but it might be nice if you were viewing the images as they were being captured.  Plenty there for me to think about, anyhow.  I need to do some research into alignment and stacking so it will have to wait for a while.  I'm trying to get my head around focus scoring at the moment.  How did I manage to do maths O-level, electronics O-level, maths AO-level, two maths A-levels (and physics too), more maths for my degree and never cover Fourier transforms?

James

I don't know   I did Fourier and Laplace Transforms - not that I can remember much now

Anyway, all very clever stuff you're doing there James

[Gina]

Yet another new shutter design.  This works the other way - clockwise for daytime and anti-clockwise for nighttime.  This takes account of the direction the motor normally turns.  Having accidentally pushed the back plate off the motor casing exposing the brushes and commutator it became clear that the motor will work better turning the designed way as the brushes are each three fine gold wires sprung from the side.  I had fun getting it back together and working

Once I get the thinner piano wire I can make a new hair spring to return the shutter to the daytime position.   To avoid having to experimemnt a lot with several springs, I have put several holes or notches for the hair spring to engage with in the shutter blade.  I don't want to have to wind up the spring more than is necessary to return the shutter blade to the daytime stop.  I have yet to add the solar film.

First pic shows the shutter blade design then 3 photos of the shutter installed on the motor pinion and in the two positions using gravity to position the shutter.  Daytime stop is the crystal on the PCB and nighttime stop is the housing.

Daytime position, crystal provides stop

Also daytime as seen through the lens mounting hole

Nighttime position showing the shutter blade clear of the sensor

[ChrisLX200]

I have to say that after using my all-sky cam tonight that the dome is a bit of a failure. Despite the heater I installed inside the casing it misted over in a circle near the top (on the outside surface), the sides were clear to about 3/4 the way up but obviously the heat from inside the casing never made it as far as the very top of the dome. To be fair it was a pretty dewey night but still, I was hoping the heat would be sufficient to keep it dew-free. Also, the colour QHY5L-II simply isn't sensitive enough for a meteor camera, it is fine as a 'cloud cam' though with 1 sec integrations - which is too slow for catching meteors. I ran this in tandem with my mono Minitron which did successfully catch some meteors, and that gets warm enough to keep dew at bay without additional heating.

ChrisH

[Gina]

I would have thought the warm air would have risen to the top and that the top of thee dome would have been warmest - strange.  Maybe increase the heating or possibly add a small fan.  I was up just after 5am and looked out and the dew was horrific.

[Gonzo]

Chris, what heater do you use please?

[Gina]

The new dome has arrived and it does have a removable inner leaving a full hemisphere of clear plastic.  It appears to be of good optical quality from looking through it.  It's quite a bit smaller than the old one (80mm v 100mm).  Looks like a new design and printing session is in prospect

I shall probably use the old dome fo one of my CCTV cameras.

The finer piano wire has arrived too so I should be able to sort the shutter out.

The casing will need a hole cutting in it (the rim and mounting are not separate like the old dome) to let the lens through.  The camera will need mounting 30 or 40mm below.

[Gina]

Been playing with piano wire and shutter.  I managed to make a spring that was weak enough for the motor to turn the shutter blade to the open position on 5v but after some time the motor started to smell and I found it was hot.  Evidently this method won't work unless I can make a very weak spring and run the motor at just a couple of volts.  Of course, motors are designed to turn continously and not be run in stalled mode   Maybe I'll order some of the finest available piano wire otherwise a total rethink is required.

[JamesF]

I think I'd be tempted to try a small electromagnet balanced by a spring.

James

[ncjunk]

Oh I like the electromagnet idea. How small do they go down to?

Sent from my GT-N5110 using Tapatalk

[JamesF]

Get yourself a bit of enamelled copper wire and a suitable size piece of iron (or steel I guess, failing that) and you can make one as small as you like

James

[Gina]

I think I'd be tempted to try a small electromagnet balanced by a spring.

James

Yes, that was the first idea I had. 

I've just tried arranging the camera at an angle so that gravity returned the shutter blade to the night position and then applied volts to the motor.  I found it needed 4v at 1.1A to turn the shutter enough.  I think over 4W dissipation in the motor coil would burn it out if left on all night.  This isn't really a very good engineering idea but worth a try

[JamesF]

I think when things are bad engineering ideas, they're bad engineering ideas for a good reason

James

[Davey-T]

How about some sort of over centre spring arrangement (if that's the right term) so that a gentle push flips it one way and a gentle push the other way flips it back, then you wouldn't need any motor stalling to keep it open/shut, bit like a sprung rocker switch.

Dave

[ChrisLX200]

Chris, what heater do you use please?

It's a dew strap (suitable for a 4" scope) inside and around the upper edge of the alloy casing. I don't use a controler for this, it's run at full power on 12V. It worked well enough that there was no dew on the casing or the lower part of the dome, just the top of the dome was misted over.

ChrisH