After far too long, our Allsky camera at Darling Hill Observatory is live. The Allsky camera takes a widefield view of the night sky every 15 seconds or so and saves the images. At the end of the night, we have it set to after sundown and before sunrise, the software will process the images into a time lapse video letting you see the constellations wheel over head. It will create start trail images showing the Earth’s rotation. And Keograms where a thin slice from the center of each image is stiched together in a time series and shows the night sky brightness throughout the night. Keograms are used to study the Aurora Borealis, but we can use them to see how the brightness changes.
The Allsky camera is running on a Raspberry Pi 4 and uses a ZWO ASI 224MC camera. The camera and some circuitry for the dew heater are in a PVC tube with an acrylic dome on top. We also added a software controlled dew heater following this Inscrutable which takes the temperature and dew point from the National Weather Service and compares it to the internal temperature in the dome. If the internal temperature gets near the dew point, it will turn a resistor array on which generates heat. When the temperature rises a few degrees, the heater is turned off. We haven’t tried it in cold weather yet, but we will have a chance in a few months. We made it modular, so changing the resistors should be pretty easy. We also found that the camera is a favored perch for the local birds, so promptly poop in it. Rather than sending Jeff down to clean, he bought a Scare Owl which lets out a screech when it detects birds. Lets see how that works.
The Allsky software is from Thomas Jacquin’s Allsky software which handles everything–imaging, processing, and presentation. It has a nice Web front end for most of the configuration and you only have to edit files for specific changes. We also split the camera functions from the web display so we have a Raspberry Pi 3 running the front end software. It should be fairly stable and any issues will be due to my very rusty Linux skills.
Just a few more things left to do. I want to add a script that graphs the temperature over time and also see if I can figure out how to determine cloudy nights from clear.
If you have any questions about this project or want to build one yourself, reach out. Happy to help in any way we can.
Thanks to those who worked on this project: Jeff Higgins (whip cracker, ladder climber and dome cleaner), Tony Krishock (solder soldier and tube crafter), John Rush (pointing and adjusting), and myself (human speed bump, assembly and software).