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Astro Projects

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All Sky Camera Mark 7

Gina

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This is my latest generation of all sky cameras and based on the ASI178MM followed by ASI185MC CMOS astro camera and a Fujinon fish-eye lens of 1.4mm focal length.  Although rated at f1.8, this lens lets a lot more light through than this would imply.  Image capture is provided by a Raspberry Pi 3 in conjunction with INDI software.  This is used with KStars/Ekos client software running on a Linux Mint desktop indoors.  Communication is via Wi-Fi.  The Mark 6 ASC has proved inadequate after being in use for some time. 

This blog will describe the problems of the Mark 6 and report my progress in developing this new version.

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Nearly down to 10°C now.  The current arrangement allows almost unobstructed airflow over the fins whereas before the table was below it so even though spaced away a bit would still have impeded the airflow a bit.  This won't arise when mounted out of doors and the nighttime temperature will be lower than the 20°C ambient indoors. 

Initial thoughts are that the cooling is better than when using the pipe as heatsink/cooler.  Should be, there's an enormous increase in surface area.  Hopefully, I should get rid of the annoying hot pixels when imaging the stars.  I have a couple of ideas if it isn't good enough.  I could cut a hole in the observatory wall beside the ASC and fit an extractor fan to blow cool air from inside the observatory over the cooler.  Or I might have another look at water cooling - I have about 4" above the position of the water block for a reservoir.  I already have a fan assisted radiator and plenty of plastic tubing that I used in my cooled DSLR experiments some years ago.

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Gina

Posted (edited)

I think it's pretty much settled down at just over 10°C so I think that concludes testing for now and I can aim to get the ASC up together enough to test outdoors tonight - probably hung on the guttering outside the living room window.  If it isn't raining!!!

 

Edited by Gina

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Made and attached the focus motor bracket and now printing a new focus gear as the spacing has changed.  This project has gone even more in the direction of "make it up as I go along", I haven't decided what the case will look like yet ?

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Gina

Posted (edited)

Cloud and rain forecast for tonight - that's because I expect to be ready for testing outdoors, of course!!  :(

Edited by Gina

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Focus gear printed and now looking into mounting and casing.  I think I shall mount it by screwing an aluminium plate onto one side of the cooler, wider than the cooler so that I can screw it to the obsy roof with two wood screws either side of the cooler.  I think the casing can fit onto the top of the cooler and stick out slightly on 3 sides.  It could be attached to the back plate that I'm using for mounting too, to give extra strength.

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Aluminium plate 200mm x 150mm x 4mm attached to cooler with M5 flat headed Allen screws.  5mm holes in plate and M5 threaded holes in cooler.

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Testing the remote focus - all fine.  Here is a test exposure 10ms, gain = 0, sensor temperature -1.5°C.  Short exposures generate much less heat.

1510746089_FocusTest01.thumb.png.bbb5d5de31ef30835a9b7f0fe776173f.png

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Tilted the camera to show more of the outdoors through the window.  Very coppery coloured sky - looks like we might get a storm.

1255939767_Screenshotfrom2018-06-1721-45-19.thumb.png.2fde6474db58b07eb917eb65ccf34421.png

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Gina

Posted (edited)

While working out the shape of the casing I've been thinking about the RPi and buck converter.  With the heat produced by the Peltier TEC heating not only the cooler but also the inside of the case it strikes me that the rather warm environment might not be good for the electronics, particularly the RPi.  Now since I'm mounting the ASC on the side of the observatory roof, the RPi (and buck converter) could be placed inside the observatory where it's cooler (and dry).  This would also make for a smaller ASC casing.  The heat leaking from the cooler into the case can help with dew heating but isn't so good for electronics.

Connecting the RPi to the ASC would be the USB cable to the camera, multiway flat cable to the focus motor and single wires for the Peltier TEC and the dew heater (if required) plus their power line (13.8v).  I can make a separate box to take the RPi and buck converter and fasten it to the inside of the roof.

Edited by Gina

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Gina

Posted (edited)

I have designed and printed the bottom part of the ASC casing and also designed the top part that takes the dome.  Now printing that.  All in natural ASA filament.

663330300_CasingBottom01.thumb.png.1a37654b8ff69b47ce3cce24d763e68c.png1091348893_CasingBottom02.thumb.png.bd3bd3ee5d072d0a0a9ee8277bac7352.png900375463_CasingBottom3.thumb.png.704d612139034a0c6629758206925a3c.png2016037482_CasingBottom04.thumb.png.e69f18f15326d6e02a93e284bee768a1.png

Edited by Gina

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Casing top has finished printing and after tidying up (removing brim) I tried it on the ASC.   Unfortunately, I forgot about the focus motor and the top doesn't fit so it's "back to the drawing board"...

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Gina

Posted (edited)

Print was fine this time :)  Some photos.  Top printed in natural ASA filament whereas bottom was white ASA.  The natural was on special offer.

769048081_CasingTop03.thumb.png.8ac2ac838c2cc4e6036dcdfd45bfa4cc.png582978019_CasingTop04.thumb.png.44a8849c86f9a5a0d8a764bef722a90b.png1202077906_CasingTop05.thumb.png.43d9d5a6aab0a9e587e3eed0e19fe7dc.png

Edited by Gina
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Getting close now to installing the ASC on the observatory and testing.  USB cable for camera and flat cable for focus motor fed out of main casing so that just leaves the installation of a 3 core flat cable for the Peltier TEC and dew heater and a case for the RPi and buck converter.  With fine weather forecast I should be up and running in a day or two.

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Cover printed perfectly and it's a perfect fit.  Been out and looked at the mounting position.  The plate should fit well onto the roof and there's even a gap where the cables can go through.  The only "fly in the ointment" is where the power cable will run when the roof is opened over the top of the warm room roof.  This is assuming I get WiFi working, otherwise there would be the Ethernet cable as well.  The alternative of the original mast (aluminium pipe) might be possible but I would need to make a waterproof box for the RPi or make a new main casing to accommodate it.  Think I'll press on with the ROR mounting.

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Making gradual progress - wiring from RPi to ASC for the camera cooler and dew heater with a connector.  Cooling connected but not dew heater yet.  I'm not even sure a dew heater will be needed but I guess I could put one in just in case.  Better to do things now rather than have to bring the ASC in later to add a dew heater.

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Dew heater done and everything connected and powered up for bench testing before going outdoors.

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Gina

Posted (edited)

ASC is working in it's permanent location on the roll-off-roof of my observatory.  Installation complete though I shall want to either rearrange the Ethernet feed or get WiFi working before using the observatory for imaging.  RPi and buck converter box screwed to the inside of the ROR and all connections made.  Powered from my main observatory supply with battery backup.

Here's a screenshot of the KStars FITS Viewer showing an image.  Exposure 32µs, Gain 0, Gamma 50.  With these minimal exposures the internal heating is negligible and the camera is running at -10°C.  The proof of the pudding will be when it's dark and I increase the exposure to 10s or more.  There is currently a 60% moon roughly due south and not due to set until 2am so no chance of seeing many stars unless I have a very late night though I could leave it running all night unattended.

Screenshot from 2018-06-21 20-58-44.png

Edited by Gina

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Gina

Posted (edited)

Light gradually going and exposure increased to 1ms.  Moon showing nicely just west of south.  Also showing redness in the haze.

1105887482_Screenshotfrom2018-06-2121-32-06.thumb.png.3f8d5be5b690ac6dae696ae97e66aef6.png

Edited by Gina

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Here is a 10ms exposure converted from FITS to PNG in PixInsight so this is the full resolution and data depth.

Light_2578.thumb.png.80994a3a27fcdf659e43c245102a16e8.png

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