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Gina's All Sky Camera - Mk 5 - with ASI178MM, Peltier TEC Cooling & RPi


Gina

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1 hour ago, Gina said:

Here is a 60s FITS capture converted to PNG.  Sensor temperature at 6°C.  Gamma = 10.  Gain on auto.

 

Still solid cloud here of course..

I bet you're wondering why the image looks a lot less sharp in the top-left than it does bottom-right? I've seen something like that when I tightened up that little screw which locks the focus, that caused the lens to tilt over to one side slightly. So I'm guessing you have something pressing against the side of the lens which is doing the same thing. That's my guess anyway :)

ChrisH

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I was wondering that - yes!  And yes the focus gear is now spring loaded with the idea of removing backlash - this is evidently not a good idea after all!  I'll put the slightly loose meshing gear back.

Clouds are coming in now - this will be the last piccy for tonight - bedtime :)  Quite satisfied with what I've got done today anyway so I shall go to bed happy :D

Just a screenshot...

2016-10-31T0025.JPG

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With good visibility today I manually focussed the ASC on a faraway hill and trees as well as I could and tonight I have it set up outside looking at a sky full of stars.  However, the focus is a bit out :(  Whether this is due to temperature or just that I'm not good enough at manual focussing I don't know.  I changed the sprung gear for the one with backlash so there's no pressure on the lens focus ring but the focus still seems worse on the top left of the image.  Now I'm wondering what to do about all this.

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Had another go at manually focussing the camera while viewing trees on far hill but it's hopeless - my hand is just not steady enough - it needs a lot more gearing down for manual control!  So I'll either have to add another pair of gears and drive shaft or go back to the stepper motor.  The stepper motor has a 64:1 gearbox and 2048 steps per revolution.  No way can I get to 0.1° accuracy by hand.  I should have worked this out before changing over to manual focussing.  Any success from manual focussing in the past must have been pure luck.

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I need to think carefully about what I want to do with the ASC.  Whilst it would be nice to be able to image the whole Milky Way in fine detail I don't really think this is the way to do it.  I think a better idea would be to use a short focus lens with my main imaging rig for this and capture a series of subs and then process these in PixInsight.

The other main use is to see how good the sky is for my main imaging so perfect focus is far less important.  I really feel that I don't want to spend time on any more refinement of this particular ASC version so I think I'll just manually focus as well as I can and leave it at that. 

I have yet to see if the WiFi will reach from the router in my living room to the RPi when it's attached to the observatory.  If not I'll set up a WiFi repeater (access point) in the observatory.

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Yes, I use my ASC for cloud-watching and for recording meteors, I focus and forget - no need to touch it again unless it's clear that focus has moved (it hasn't yet despite needing to carry it outside every night).  That camera records the whole session to disk. The second cam I have attached to the scope with a 6mm lens which tracks with the scope and provides a wide field view of the part of the sky I'm imaging in. It's useful to see exactly where I'm pointing, avoiding obstructions, whether the mount slews when I ask it to, whether it's really done an automated meridian flip :) and whether a satellite/plane went through the FOV or just missed. Makes little difference if you are running automated and leaving it to its own devices but if I'm in the Obs watching then I will stop/start the sub if something untoward happens. I have a second ASC (180deg FishEye) which now sits outside 24/7 and this one I can monitor from the house to remotely check weather conditions. It doesn't record to disk I just use the live view when needed.

ChrisH

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ASC now in its permanent location on the observatory and the WiFi is working fine :)  Moved following a heavy rain shower so there's large raindrops on the dome.  I'll now switch on the high power raindrop drying heater...

Capture 08.JPG

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The rain has stopped but the atmosphere is very damp.   Had a look outside and there's complete cloud cover.  Somehow the ASC can see through light cloud - maybe picking up infra-red as the camera does not have an IR filter.  This is the first night-time image with the ASC in its proper position.

Capture 12.JPG

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With the ASC in its permanent position and performing satisfactorily I think I can declare my All Sky Camera Mk 5 - FINISHED :)

I shall continue posting the images from the ASC in this thread but I don't envisage doing any more work on it.

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Looks like I might be doing some DSO imaging tonight after all - the sky is clearing :)  Here is a 30s image followed by a 60s one, gain of 210 and gamma of 10.

Capture 14.JPGCapture 15.JPG

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Still doing its job though - tells you it's raining out there :)

Mine has got moisture inside and I'm pretty sure it's from where the cable enters the case underneath which I never sealed properly. I'm guessing the silica gel has become saturated so I'll have to pull it apart, regenerate the silica gel, then make sure I seal it better.

ChrisH

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I had thought of sealing mine but decided it was too difficult so rely on the heating to keep dew at bay.  Also, any damp inside I would expect to condense on the outer casing of the camera where it's cooled by the Peltier TEC and if there was enough it would run down into the bottom of the case.  Even without any extra heating the electronics and Peltier TEC produce heat within the case which can rise into the dome. 

Having put the ASC plus mast in position the appearance is not ideal - a black rectangular box on the mast looks a bit odd and not very pretty.  I guess that doesn't really matter but the windage will be a lot more than with my previous cylindrical designs of case.  Probably not worth the effort of 3D printing a new case but it is something I might consider.  A nice cylindrical green one to match the shed observatory would look better :D   I think it would be possible to seal this sort of case too.  The dome could have a rubber seal and clamp arrangement and I could probably do something similar with the mast to case interface.  Otherwise there's only the power cable to seal and that could be with a grommet.

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