Where the Radio Pointed While the Stars Turned

Okay so here’s what’s been rattling around in my head all afternoon: you can draw lines on the sky without a laser. Not metaphorically. Actual lines, rendered as glowing arcs across a star-trail photograph, each one pointing toward someone I talked to on the radio.

Let me back up.

When I work HF—the short-wave bands, the ones that bounce off the ionosphere and let you chat with people five thousand kilometres away—every contact gets logged with a grid square. It’s called Maidenhead, this system, and it carves the entire planet into rectangles using alternating letters and numbers. HN05 is somewhere in the North Atlantic. EN34 is Minneapolis. PM95 is deep in Japan. When someone answers my CQ and tells me their grid, I’m not just writing down who they are—I’m writing down where they are, whether I think about it that way or not.

And here’s the thing: given two points on a sphere, you can compute a bearing. Not a flat-map bearing, because those lie—a great-circle bearing, the direction you’d start walking if you wanted to take the shortest path. Radio waves mostly follow great circles. So when I worked a station in Scandinavia last week, the signal didn’t go east. It went north, skipping off the aurora zone, arriving from an azimuth of maybe 012°. Northwest gets you Japan. Southeast gets you Chile. Every conversation has a direction.

You’re probably thinking: okay, but why would anyone care about this? Fair question. I didn’t care either until I was stacking star-trail exposures last weekend and noticed the obvious: the stars rotate around Polaris, my antenna points everywhere, and those two facts could live in the same image.

The pipeline—and I’m sorry, I know I keep building pipelines—is embarrassingly simple. Export the log as ADIF (a plain-text format that’s been the standard since 1996, somehow). Parse out the grid squares and timestamps. Compute the azimuth from my QTH to each grid centroid using spherical trig. Plot those bearings as radial arcs from centre, tinted by band or time or whatever aesthetic I’m chasing today. Composite the result over a star-trail stack.

What comes out is a photograph that says: while the sky was turning, I was talking that way, and that way, and that way.

The subtlety that tripped me up immediately—and this is the kind of mistake I only catch after staring at the result and thinking something’s wrong—is magnetic declination. Alberta sits about 14° east of true north right now, and that number drifts slowly over years. If I compute a true bearing from the grid math and then plot it without adjusting, every arc rotates clockwise by roughly one hour on a clock face. The image doesn’t break. It doesn’t throw an error. It just quietly lies about where the world is. I love this kind of bug. I also hate it.

When I built the Morse beacon for star-trail lightpainting, the LED’s blink pattern was the content—the photograph was just the canvas holding it. This is the inverse. The stars are the content, and the overlaid arcs are a commentary, a whispered confession about what I was doing while the sky turned. Both hobbies use the same stacking workflow; both turn invisible things (callsigns, radio paths) into something you can see. But this one is retrospective. The data already exists in the logbook. I’m just finally asking it a geometric question.

Long-path contacts complicate things. A station in England might arrive from 048° if the signal went the short way, or from 228° if it bounced the other direction around the planet. Most logs don’t record which path worked. So sometimes the arc I draw is pointed exactly backwards, a line toward where the signal didn’t go. I could mark it as ambiguous—draw both possibilities—but that clutters the image. For now I’m guessing, which means the overlay is part truth and part hope. Maybe that’s honest enough for art.

There’s precedent for this, by the way. Hams in the 1950s printed polar projection maps on their QSL cards with hand-drawn radial lines to every station they’d confirmed. Same idea, different tools. I’m not inventing geometry; I’m just automating what someone’s grandfather did with a ruler and a protractor.

The first overlay I finished is on screen now. Eight contacts over two hours, eight arcs, Polaris at the centre like a compass rose. The stars make their concentric circles; the radio bearings cut through at angles. One arc points almost due north—that was Sweden. One points southeast—Argentina, surprisingly loud on 20 metres.

I don’t know what to do with the image yet. Print it, probably. Frame it, maybe. But the satisfaction isn’t in the output. It’s in the question the overlay asks: where were you looking while the Earth turned?

I have fifteen years of logs. Thousands of contacts. Each one a bearing I never computed. Each one a line I never drew.