How to make a simple all-sky camera | Hacker News Reader

How to make a simple all-sky camera

skyatnightmagazine.com

134 pointsjacquesm18 comments

I made one a couple years ago to watch the clouds sail cross the sky. After a few weeks I noticed scratches in my acrylic dome. On review I have some nice picture of the feet and claws of juvenile bald eagle.

Sacrifice a bit of your horizon to make a perch higher than your dome.

Oh that's almost as cool as seeing a meteor. Not sure which are rarer even. No bald eagles here so I should be safe but it's a good point that you may want to investigate the local wildlife before staring on a project like this.

Bald eagles are everywhere in Maine now. Near a tidal estuary near us we counted 25 sitting in trees watching the smelt run.

I initially read your second paragraph as, "Sometimes you have to sacrifice your view of the horizon to catch an eagle."

For a while, I wanted to make one of these for day-time use, to measure cloud cover and maybe get daily/weekly averages. Then I realized that solar panels make a great photo-diode for measuring light intensity. You just need a bit of math to account for ephemerides (sunrise/sunset in particular) and angle of exposure.

You can get surprisingly good results with throwaway hardware. A few years ago I did an all-night time lapse of a night-blooming cereus opening up its once-yearly flower. $10 throwaway 480p webcam on a cheap tripod, old laptop running a script to capture every few minutes, old incandescent lamp to keep the thing lit through the night. Fed all the images into ffmpeg (with some noise reduction, I think?) and found the output looked almost professional, apart from the low resolution.

I've recently used na RPi4 with a ArduCam OV5647 camera and a LS-40180 Fish Eye CS mount to make a home security cam as a fun project. Works nice and has a 194 horizontal / 142 vertical FOV.

I wonder if that setup would work for something like this? Does anybody have experience using cheap RPi-like equipment for things like these? Am I correct in assuming that this wouldn't work because of the low sensitivity of the sensor in the cam (I know next to nothing about photography)?

Your camera is your limiting factor here - at 5MP, and ¼”, you have some pretty small pixels. The dark current etc. is unspecified in the spec sheet. The lens is small. Together, that means low photons per pixel, and noise becomes dominant.

You would probably be able to image something, but you’d want a bigger sensor and lens ideally.

That said, you can still do plenty if you’re willing to set the thing up on an electronic equatorial mount (very cheap and cheerful would do for wide angle) and take many long exposures, and stack them - but the moment you try it with better gear you’ll be wishing you hadn’t bothered!

Oh, ok. Assumed that this would be too good to be true. Thanks anyway! The equatorial mount would be nice but I thought more along the lines of making a one-off night sky time lapse video out of curiosity. I gotta stop buying hardware for one-off fun projects, so this will probaly remain a "some day, maybe" that never gets done ;)

I'm assuming the dark current is what the camera picks up even when it's 100% dark? Also, I would need a bigger lens so that I can capture more light right?

Why take a video instead of just capturing stills and stitching them together, assuming the end result is a timelapse?

I guess if you've got the storage space and processing power for it, but it just feels a little wasteful.

I have a Meike 6.5 mm lens for my Fuji X-T3 and have done quite a few time lapses with this setup. It’s fun to see how the Milky Way rises and you also get good sense of how the sky rotates around North. The lens is around $150 so not too bad.

Does anyone know good beginner resources or youtube channels to learn about astronomy?

I liked this book: https://www.amazon.co.uk/Sky-Users-David-H-Levy/dp/052145958...

A nice set of binoculars (something like 8x50 or 10x50) can be had cheap and will help you learn your way about.

Anyone know of some software to spot interesting things? Or do I have to train my own neutral network on what is normal/uninteresting with hours of "boring" sky?

Stellarium - https://stellarium.org/

A simple way would be to see if the color histograms of your image deviate by a lot in a short period of time.

If you have an iPhone the Night Sky app is pretty incredible. It's not the most intuitive but it has a really good AR function that lets you point it up at the night sky and it will help you find anything from planets to stars to satellites.

The article is comically incomplete:

> The complicated part of this arrangement, if you want to have a go at building one yourself, is the enclosure.

> Consideration needs to be given to full weatherproofing and heaters need to be fitted inside the dome to keep it dew free.

> We’re going to simplify ours by dispensing with the enclosure completely.

They need to collaborate with some makers with a 3D printer.

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