How to choose your sky
Pick the date and local time as they were where you were standing — the time on the clock there, not UTC. Search for a city, or type latitude and longitude for anywhere else; the time zone fills in from the place and you can change it. Daylight saving time is handled for you, including the awkward hour when clocks change: if the time you enter didn’t exist, or happened twice, a note says which moment was used.
The map is the sky as you’d see it looking straight up: the centre is directly overhead, the edge ring is the horizon, north is at the top, and east is on the left (the opposite of a ground map, because you’re looking up, not down). Stars below the horizon at that moment aren’t shown.
Stars, lines and the Moon
- Faintest star sets how deep the map goes. Bright stars get bigger dots. Where faint stars would crowd closer than a nozzle can print, the closest are dropped and the notice tells you the faintest star kept.
- Constellation lines connect the traditional 88 IAU patterns; names label them (small — best on 140 mm plates and up).
- Moon marks where the Moon was. It’s a marker only: the phase isn’t drawn.
Print settings
- Orientation: flat, face up, directly on the bed. No supports.
- Nozzle and layers: 0.4 mm nozzle, 0.12 mm layers. The smallest raised dots are 0.6 mm wide and the smallest backlight holes are 0.8 mm.
- Raised domes: print a dark plate with light stars for the best contrast. For two colors, turn on the two-color option, export the 3MF, and give the plate and the stars different filaments.
- Holes for backlight: use white or natural filament and a plate of 2–3 mm; hold it in front of a light. Constellation lines and names are shallow engravings that don’t break through.
- Captions wrap around the rim and shrink to fit; keep them short for a 120 mm plate or smaller.
FAQ
How accurate is the sky? Star positions come from the Hipparcos catalogue and are computed for your exact moment and place; they agree with an independent calculation to well under a hundredth of a degree — far finer than a print can show.
Does the site look up my location? No. City search uses a list that’s bundled with the site and only downloads when you search; nothing you type is sent anywhere, and the site never asks your device for its location.
Why are some stars missing that I can see in the sky? The catalogue goes down to magnitude 6 (roughly the limit of a dark, clear sky), and faint stars that would overlap on a small plate are dropped — a larger diameter or a smaller star size keeps more.
Why is east on the left? Because the map shows the sky overhead as you look up. Hold it above your head, facing south, and it lines up with the real sky.
Can I put a date before 1900 or after 2100? Not currently — time-zone rules for those years aren’t reliable, so the range is 1900–2100.