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All Sky Camera Revisited


Gina

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Power wired to HAT plus Peltier TEC and dew heater wired up.  Connected the water pipes to the waterblock and screwed the mounting part onto the box.

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Done some more wiring up and sorting out the final arrangement but still waiting for the replacement RPi 3B+ due today.

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Out for delivery
Now estimated 7:30 PM - 9:30 PM

 

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The new RPi has arrived, I've set up WiFi and have it working with the camera and lens so now have the ASC working in its "naked" state.  Adjusted the focus as I had knocked it.  It's a very delicate operation to do by hand and I'm wondering whether to reinstate remote focussing.  Something to look into. 

Installed the bare camera and lens unit back on the observatory corner post.  Here's an image.  Think the focus is a bit off but I'll see when the stars appear.

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Edited by Gina
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Night view.  Focus isn't bad.  Sensor temperature is 16°C but not showing hot pixels all that much.  I'm wondering if I might have "over engineered" the cooling as this is with only ambient cooling on the open case.

1589536923_Screenshotfrom2020-05-2422-55-10.png.ef5f6328181113e95b0784bf722dec8c.png

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Been doing more wiring up on the ASC.  I reassessed the power requirements and realised that the 5v load was more than I had originally catered for.  An RPi 3B+ takes up to 2.5A and the Peltier TEC on LOW (5v) a little under 1.5A.  The buck converters are rated at 3A and not sufficient for the possible 4A so I need 2 - one for the RPi and the other for the TEC.  I now have two buck converters wired in.

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You need a 5V, 2.5 Amp micro USB power adapter for powering your Raspberry Pi 3 Model B and Raspberry Pi 3 Model B+.

 

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Wiring finished, parts assembled and attached to the mast then mast attached to north wall of the observatory.  Power cable run to the power distribution box in the warm room and water circulation arranged.  The camera sensor temperature started at 26°C but with the Peltier TEC cooling and water cooling of the TEC hot side the camera is now down to -12°C.

Here is a screenshot of KStars/Ekos running the ASC.

1494212686_Screenshotfrom2020-05-2620-47-10.thumb.png.084f98e336206010c896797fc93fbce2.png

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Dew heater isn't working.  I'll sort it out tomorrow.  I've turned the cooling off and hoping the heat from the camera and RPi etc. might warm the dome.

128109899_Screenshotfrom2020-05-2621-20-27.png.510890b00c592d1da41a0c330d19176e.png

Edited by Gina
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The focus isn't good either.  I may have to arrange remote focussing like I have on my main astro imaging kit.

 

Edited by Gina
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Now it's almost dark I can see all the things that need fixing!! 

  1. Latest is that the power LED on the RPi is illuminating the dome!
  2. Dew Heater
  3. Focus
  4. Looks like a hair on the lens

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Now have the ASC complete with mast indoors.  There is muck on the outside of the dome as can be seen here.  Just hope that when I get the dew heater working and no dew on the outside of the dome that this doesn't happen again.  I didn't get any muck on the lens when I was using it uncovered overnight.

1772869112_Screenshotfrom2020-05-2710-12-24.png.d36d95a3e83262fa942ad7388e4c9f2a.png

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Cleaned the dome with water and it's nice and clear now.

Next to the dew heater.  Looks like the IRLZ44N has failed from testing with DMM.  Thought I had some but can't find any.  Looked at buying some but several days delivery.  The IRFZ44N is also suitable for this application as there's plenty of voltage available and these are both cheaper and shorter delivery.  Ordered some with delivery by Tuesday 2 June.  Meanwhile I could connect the dew heater in parallel with the Peltier TEC to get it working.

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Connected the dew heater across the Peltier TEC connections  and put some black goo over the red LEDs.

Next to put it all back together and see if I can get sharp focus on distant trees.  Then put the cover back on and check that the image is still in focus with the dome on.

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Refocused and replaced cover with dome.  Focus changed a bit with the dome.  ASC now back on observatory, all connected up and working.  Just waiting for dark to see if I've cured the problems.  The current reading on my power distribution box confirms that both TEC and dew heater are drawing current.  2.5A TEC and 1A dew heater, total 3.5A.

328400915_Screenshotfrom2020-05-2720-47-01.png.7b319092ceec2396486ab58d03f41e46.png

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Daytime image (just captured).  Exposure 32µs and gain of 0.  For nighttime when fully dark I use 60s and gain of 102.

1531142293_Screenshotfrom2020-05-2811-25-28.png.25d342f053bae852112b4ebff400154a.png

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Here is the ASC on its mast on the side of the observatory.  The mast wants cutting down by about a foot.  On the bottom of the ASC casing is a glass jar with colour-change desiccant which I can see while sitting on my settee through the east window (with binoculars).  Still orange ATM so dry.

69748292_ASCMast01.JPG.83b44e2dce18d8044380e2147d337010.JPG

Edited by Gina
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Popped out to the observatory and looked at tidying up the ASC water cooling system.  The radiator and fan unit could be mounted on the intermediate wall between scope room and warm room, with the warmer air from the radiator going into the warm room avoiding any possibility of warm air spoiling the imaging as well as being a simpler way of mounting the radiator and fan unit.

For the water reservoir I have a 2lb jam jar which I plan to mount by the lid with holes for the water pipes and pump wires, with the pump sitting in the bottom of the jar.  That should reduce the loss of water due to evaporation which has been occurring with the open top saucepan I have been using as a temporary reservoir.

Edited by Gina
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Looking at the mast/pipe and where the water pipes and power cable now go through the observatory wall (moved down to clear the roof), I think I shall cut off something like a foot from the bottom.  I have yet to measure the excess height of the ASC and hence the amount to cut off.  Hoping to do that a bit later when it's cooled down a bit.

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 Measured the amount to cut off the mast to bring the ASC to just above the highest point on the roof.  About 16" or 400mm.

Colour change desiccant is still orange so casing is airtight.

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