Building an inexpensive lux meter for the observatory…

As part of an environmental monitoring system for an observatory, I wanted to include a measure of ambient light. Ostensibly, this is for safety reasons. However, I must admit that I really just want to see if I can (coarsely) measure sky brightness. There are a number of inexpensive light sensors available from AliExpress/Amazon. The…

How to find stellar magnitude limit – A bit of a hack

Finding the stellar magnitude limit in an image is not necessarily as straightforward as it, at first, appears. I needed to come up with some non-hand-wavy numbers and thought, ‘No problem, this is easy.’ It turns out that I was wrong. At least for my imagery and what I wanted to say about it. The…

Cloud monitor MKII (now with POE!)

After building the Mark I cloud monitor, I realized that I really wanted something with power-over-ethernet (POE). The cheap network adapters that I use typically have an HR911105 (or similar) RJ45 connector which is not compatible with POE. I’ve looked but have yet to find any of these adapters with POE, so I decided to…

Building a network-connected cloud sensor (MKI)

I’ve wanted to build a cloud sensor for years now, but never actually found the time to do it. So, after seeing IR sensors for something on the order of $5 a piece, I ordered a couple and thought that I’d give it a shot. This has undoubtedly been done by lots of other people,…