Gina's DIY All Sky Cam - Complete Redesign

[Kropster]

Gina, which printer do you use?

Would you recommend it?

[Gina]

I use the UP! Plus 2 and yes I recommend it   Accurate printing and easier to set up than the Rep Rap types.  Better software, easier to use.  But the print volume is less than Rep Raps - about 130mm cube as opposed to many Rep Rap printers of 200mm cube.  And relatively expensive.

[Gina]

Been thinking about the shutter control circuit.

This arrangement would have most of the components in the camera box with just switches separate, maybe in a little control box.

This puts the switching in the positive side of LDR and meter and moves some components from the camera box to the control box.  This would also enable use of the LDR as "end of night" sensor to instruct the automatic observatory control to close down after a night's imaging session.

This is a slight rearrangement.

[Gina]

Focus knob printed plus test support bracket to connect box to mounting ali pipe.  Design corrected slightly and I've been printing in black ABS but black often causes problems and has again - hot end blocked   So I now have to remove the printer extruder assembly and clean it out. Groan...  I'll go for another colour when I've fixed it.  Even with this particularly "user friendly" 3D printer, there's still the odd bit of servicing required.

Found what seems a suitable resistor to provide dew heating - a 68 ohm 10W ceramic resistor.  This will give 2.8W on the 13.8v supply.

[Gina]

Now looking at the wiring up and mounting the dew heater.  I'll go for the option of switching the +ve side of the LDR and meter movement with the zener diode and 560 ohm resistor mounted on the switches.  That seems easier and more versatile in case I want a different design in the future.  This means the only components that need mounting in the camera case are the dew heater resistor and the LDR.

I have a reel of 6 core security cable I bought for my CCTV cameras etc.  This will easily cover the extra connections into the scamera box (in addition to USB).  I only need 4 wires so I'll double up on the dew heater connections since that takes most current.

[Gina]

Wiring up.  The wires will be tucked away when the unit is assembled and will not be against the dew heater resistor, the meter movement or the focussing gears.

[Gina]

I think construction is complete   I'm now testing.  I have wired up the mode control to run in daytime imaging mode.

I brought the laptop in from the warm room for testing the all sky camera.  Couldn't get it to work wwith PHD so I tried SharpCap and that worked   However, in spite of having the same lens to sensor distance as before I couldn't get it to focus - focus seemed to be way off one end of the adjustment range   Have to sort that out - I was hoping to try it on the stars tonight but it was not to be   Oh well... tomorrow is another day...

Clear sky tonight so I've now set up for galaxy imaging with the laptop back out in the warm room.  Have to sort out another computer to continue all sky cam testing.

One thing I did confirm was that the remote shutter control works fine - that's a step forward

[Gina]

I tried my Asus netbook tonight but SharpCap on that wouldn't display properly - gave an image like a TV set with line sync problems   I'll bring the laptop indoors tomorrow and continue testing with that.

Clouded over now so galaxy imaging also ended. 

[Kropster]

It's never straight forward, is it?!

Computers can be so capricious. One day all is fine....the next they have a sulk.

[Gina]

Oh so true

[Gina]

Now have my imaging laptop indoors, running SharpCap.  Unfortunately, the exposure won't go low enough for daylight imaging   When I did daytime imaging previously, I used the Baader Solar Film filter which has to go close to the image sensor with light proofing all round.

I think the QHY5 is probably just too sensitive for daylight imaging without a high power ND filter or a lens with small aperture.  Maybe a standard webcam would be better for daylight imaging.

[Gina]

Now trying PHD2 and have it working - I had to select ASCOM camera rather than QHY5   However, the minimum exposure is still 1ms which is the limit for the camera I believe, and that is still far too much.  I've tried putting Baader solar Film over the lens but there's far too much light getting in - the camera is not in a totally lightproof enclosure.  Seems the only way to use the QHY5 and f1.4 fisheye lens for daylight imaging would be to have a solar filter lightproofed to the sensor.

Oh... curses...  Without a redesign it seems daylight imaging is out   That makes setting up difficult even if I use the camera for night-time only.  The shutter will still be useful for darks and I can use the LDR for closing the shutter during daytime to make sure the QHY5 is totally safe in sunlight.

When I think about it, I should have known I have far too much light in daylight.  When using astro cameras with a scope in daylight for setting up I need to cut the light down even at f5 let alone f1.4

[Gina]

I've dismantled the unit to find the cause of the focussing error and I've found it!  Remarkable.  I did a close comparison between the original QHY5 PCB to lens box and the current one and found a discrepancy   The thickness of the top is slightly different.  I think I can use the original without needing to reprint anything (any more plastic printing is awaiting an extruder service).  Good job hot-melt gluing can be undone and redone relatively easily

[Cath]

Redesign no.2 coming up

[Gina]

Maybe some time in the future but not yet

Actually, I would prefer a colour camera for daylight to distinguish between blue sky and flat cloud.  I'm thinking of a colour webcam for daytime use - just need to find a fisheye lens that will produce a small enough image for a 1/4" sensor   This would be a totally separate all sky camera.

[Gina]

With daylight imaging dumped, the modes go down to two - night-time light subs and dark subs.  Here is the revised mode switching circuit diagram.

[Gina]

Well...  I've succeeded in wrecking the meter movement   So that's that!  Onto another project.

Thank you to everyone who has replied in this thread

[Cath]

Maybe it's time to take up knitting eh Gina

[Kropster]

Maybe some time in the future but not yet

Actually, I would prefer a colour camera for daylight to distinguish between blue sky and flat cloud.  I'm thinking of a colour webcam for daytime use - just need to find a fisheye lens that will produce a small enough image for a 1/4" sensor   This would be a totally separate all sky camera.

There must be some fish-eye security cameras out there that would do for daylight?

Myabe knitting is a good idea!

[Horwig]

Well...  I've succeeded in wrecking the meter movement   So that's that!  Onto another project.

Thank you to everyone who has replied in this thread

Well, if we put your wrecked meter movement with my wrecked qhy5, we're well on the way to a full wrecked ASC, anybody got a wrecked fisheye?

Huw

[Gina]

Done knitting

Serviced the printer but it's still not quite right - have to strip it down again I guess - I'll fix it, done so several times before.

Extracted the meter movement from the rest and unsoldered the wires.  Then examined it with closeup glasses and 3x magnifier with light.  Problem was a combination of hot glue in the wrong place and buckled plastic round meter movement.  Removed both, fixed a wonky coil spring and it's now free   Next job will be to wire it back up and see if it's working - feeling confident but fingers crossed

A bit later...  wired up and it's responding to current   Now to glue it back onto the casing

[Gina]

Meter movement glued back on and shutter adjusted plus backstop glued on (sets "closed" position of shutter blade).  Tested for operation and PASSED

[Gina]

I have it working - sort of   On the living room table pointing out of the window.  Here's a screenshot of the PHD2 display via TeamViewer.

[Horwig]

good work Gina, do you ever give up?

Huw

[Gina]

Give up???  What's that?

Another capture...  There are a couple of stars showing   You can also see the top of the window, the curtains and curtain rail, the ceiling and light fitting and a few other bits in the room.  The ceiling is being lit by the television