Phil's Astronomy Blog: Astronomy, IoT and the Mesh

Well alright! My observatory now has an atmospheric sensor watching over it - temp, humidity, pressure, dew point, the works - so I know exactly what conditions my equipment is sitting in, whether I'm out there or not. Dew especially is the enemy; sneak up on a mirror or a lens overnight and you've lost the session before you even started.

I run things remotely a fair bit, so "having an eye on things" from anywhere became a real need. Sure, you can buy an off-the-shelf solution for this. But I wanted to build my own, and that meant finally putting my radio hobby to work for my astronomy hobby.

But first, what is this all about?

Here's the quick version of the tech behind it, for anyone curious how this actually works: I've been messing around with LoRa lately - "Long Range" radio, which trades speed for distance and battery life. Instead of a strong, fast signal like WiFi or Bluetooth, it spreads a tiny bit of data across a wide range of frequencies really slowly, so a receiver can pick it out of the noise from miles away on barely any power. You're not streaming video with it, just small chunks of data - but you can send them from a hilltop to a valley ten miles off on a radio running off a coin cell for weeks. Kind of the same idea as those FT8 signals bouncing off the ionosphere, except here it's your neighbor's radio doing the relaying instead of the sky.

Diagram shows that while Bluetooth and Wi-Fi are fairly tightly bound to a small area from any given device, LoRa is way more expansive.

Two projects are built on top of that raw ingredient: Meshtastic and Meshcore. Meshtastic's the older, more established one - every node relays messages for its neighbors, so a message hops node to node well past your own radio's range. No cell towers, no internet, no monthly bill. Meshcore's the newer kid, same basic idea, but with a more efficient routing philosophy and encryption baked in from the start. Both are still actively evolving, so which one wins out - or whether they just end up serving different niches — is still an open question..

Meshtastic floods every message through all nearby relays; Meshcore routes it along one known path.

I've since built up a handful of nodes and repeaters on both. Meshcore feels "cooler" to me - easier interface, livelier crowd, just makes more sense overall - and I've reached people up to 110 miles out on it. Meshtastic doesn't see much local activity, so that one became my own private mesh instead, which is exactly what the observatory project runs on.

My Meshtastic node, which I can access via the Meshtastic app on my phone. This is Heltec v4 board.

A view of Mestastic repeater node which sits on my chimney.

For the actual build: I picked up a Heltec v4 board and an M280 climate sensor, wired them together, and added a battery, high-gain antenna, and a charging setup tied into the observatory's solar charger. It took some tinkering, but now that node reports temp, humidity, pressure and dew point every thirty minutes - hopping from the observatory to a repeater on my roof, then to the node on my phone. The whole thing runs off a little 3.7v 1100mah battery kept topped up by the observatory's own solar charger.

Solar power control unit on the left, the Meshtastic climate sensor I constructed on the right.

So now, wherever I am, I can check exactly what's happening inside the observatory before I even decide whether it's worth opening the roof - no internet or cell service required, since it's all running on my own infrastructure. Bit of a rabbit hole to get there, but a genuinely useful one - and a nice reminder that the "astronomy hobby" and the "everything else hobby" aren't always as separate as they look.