All sky cam project

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KathyNS Canada
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All sky cam project

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Post by KathyNS »


I had an ASI120MC that mostly gathered dust except for a short time around planetary oppositions. And I had a curiosity about what the weather was doing during my imaging sessions, not to mention a desire to capture cool images of fireballs and bolides. Which adds up to building a sky cam.

I bought a large weather-proof junction box from Home Depot, and ordered an acrylic dome from Blue Robotics. I built up a small wooden structure within the junction box to ensure that the camera was flush with the top surface. The acrylic dome is attached with six screws, and sealed with silicone.

The dome needs a dew heater, so I got eight 7.5-ohm resistors and wired them in series. With a 12-volt (nominal) power supply, this gives me about 2.5 to 3 watts of heating. Note that the dew heater cannot be a retrofit. It has to be installed before the dome is sealed to the box!

The heater is controlled by the Aduino that operates the observatory's power relays. It is programmed to turn on the heater if the temperature-dewpoint spread is less than 2 degrees Celsius, or if the wet-leaf sensor detects dew, provided that the air temperature is less than 30 C.

The unit sits on the roof of the observatory. It is tilted at a slight angle by the slope of the roof. This actually works well, since the stock 2mm fisheye lens that comes with the ASI120 does not cover a full 180 degree FOV. The tilt aims it towards the open sky.

Overview of my sensor suite. At left, on a stalk, is the Hydreon RG-11 rain sensor, used for the dome's emergency close system. Middle, just above the smaller junction box, is the wet-leaf dew sensor. At right, with the thick conduit leading to it, is the sky cam.
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Closeup of the sky cam unit, showing the dew heater resistors. The temperature-humidity sensor is on the far side of the unit.
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Sample image. The cardinal points are at a 45 degree angle because I had to rotate the camera in the box so the USB connector would fit! My darks don't seem to be working, so there are a lot of hot pixels showing. Vega is the bright star at the 5 o'clock position relative to the zenith ('Z') mark. Jupiter is nearing south ('S'), and the Moon is rising in the southeast ('SE').
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Image
DSO AP: Orion 200mm f/4 Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,Oiii,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on HEQ5 pro; C-90 on wedge; 20x80 binos; Etc: Canon 350D; Various EPs, etc. Obs: 8' Exploradome; iOptron CEM60 (pier); Helena Observatory (H2O) Astrobin
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