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Gina's All Seeing, All Singing and All Dancing All Sky Camera


Gina
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This is my latest build of an All Sky Camera and has a few extra features over previous designs.  Most notably, a cover over the dome to keep UV from yellowing the dome in sunshine (yes we do get it sometimes) and to keep dirty rain off it.  This will be remote controlled.  The other addition is internal and is remote focussing which experience has shown to be desirable.  The ASC uses an astro camera (ASI178MC) and a fish-eye lens giving a full 180° sky coverage - horizon to horizon. 

The camera is not a cooled version so to reduce noise and hot pixels when taking nighttime images of 60s I have added Peltier TEC cooling applied to the camera case.  The latter has a 3D printed casing and support which also provides thermal insulation.  The hot side of the TEC is water cooled providing very efficient camera cooling.

With all these extra features over a standard ASC I think it deserves the title of the topic.

I'll post screenshots of the CAD model shortly.

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The bearing brackets for the cover axle needed moving inboard to allow for rounded corners on the box.  Also to get the drive from one side to the other I've added bosses to the drive gear and the lever on the other side.  I've checked that the parts fit and will be assembling it shortly and take a photo or two.

1499345456_Screenshotfrom2020-10-0216-08-52.png.08afe7a66aac36c53949902a692601bc.png

572626804_Screenshotfrom2020-10-0216-06-54.png.8abc3dd83d7669813febf103938f2772.png

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I have the cover system assembled and attached to the box but the torque required to open and close the cover seems more than I expected and I shall need either a more powerful motor or a lighter cover.  The current one covers the dome clamp ring as well as the dome itself and I think that may be unnecessary.  A smaller cover will be both lighter and have less windage.

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Even with a smaller dome cover I'm not really happy to use a 28BYJ-48 stepper motor and I tried a NEMA17 in the box and I think I could fit one in the box and still have room for everything else. I usually believe in over-engineering everything.  Adds reliability.

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A NEMA17 is very slightly too big to fit between the box lid overlap and projections in the bottom of the box.  However, I reckon I can remove or reduce that relevant projection to get this size motor to fit.  Knowing how powerful the standard NEMA17 is, I feel happy that I shall have enough torque to open or close the cover.  I have several spare motors.

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Posted by: @MarkAR

Superb work Gina. Did you manage to get the weight down enough for the little motor or are you squishing in something beefier?

Thank you Mark.  The weight is vastly reduced but still decided that the little motor would be a bad idea and I'm fitting a 40mm NEMA17.  I removed a projection in the bottom of the box and there is now plenty of room.

 

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I have fastened the NEMA17 into the box.  I have also confirmed that all the electronics will fit in the box.  Actually, I may change the RPi 3 B for an RPi Zero as I only need one USB port, for the camera, no Ethernet and all other functions are covered by the GPIO pins which are the same.  This would free up the RPI 3B for something that needs its extra features such as astro camera capture, as well as taking up less space.

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Couple of photos of the focussing system. These photos also show the camera and thermally insulating casing.

Inside of lid showing focus motor and lever.
https://stargazerslounge.com/uploads/monthly_2020_10/1694257569_FocusMotor.JPG.7cfcf8a09a90476c2bdf2e505164e95e.JPG

Top view showing focus lever on lens focussing sleeve.
https://stargazerslounge.com/uploads/monthly_2020_10/261872861_FocusLever.JPG.69c6afb15179558738d98b1c034f0918.JPG

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I have the main board designed and built and I'll come to that later.  I need an extra circuit board to carry the stepper motor driver modules.  These are A4988 as often used in 3D and in fact these come from an earlier version of the 3D control system for my 3D printers.

This is a connection diagram for these driver modules.

965219599_Screenshotfrom2020-10-1914-12-51.thumb.png.55405455c366d35863ea95d9e5b64b39.png

 

Next, the layout of the extra circuit board produced on stripboard (eg. Veroboard).  The drivers share the 100µF electrolytic capacitor.

ASC_Layout.png.c84f27922ed29f11cd77aa33c28c6efd.png
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