Two limits apply and you always get the smaller. The sky here has a ceiling of magnitude 6.56, set by the meter reading above. Your eyes have a floor, and for the first twenty-five minutes outside it is the floor that binds — which is the whole point of a place like this. What you see is limited by how long you have waited, not by where you are standing.
| Minutes outside | Limiting magnitude | Stars above the ridge |
|---|---|---|
| 0 | 2.00 | 19 |
| 3 | 4.20 | 271 |
| 7 | 5.20 | 890 |
| 13 | 6.00 | 2,264 |
| 20 | 6.45 | 3,617 |
| 25 and after | 6.56 | 3,872 |
Nobody is asking where you live. These are nine skies drawn by the same engine that drew the one above, differing only in the meter reading fed to it. Find the one that looks like home. Bortle 2 is what is over this property; Bortle 9 is a city centre, and the difference between them tonight is a factor of 31.7.
Bortle 1
3,962
22.00 mag/arcsec² · limit 6.62
Bortle 2
3,872
21.85 mag/arcsec² · limit 6.56 · here
Bortle 4
3,009
21.30 mag/arcsec² · limit 6.28
Bortle 6
668
19.25 mag/arcsec² · limit 4.96
Bortle 8
211
18.00 mag/arcsec² · limit 3.97
Bortle 9
122
17.50 mag/arcsec² · limit 3.54
Timed against astronomical dusk rather than the clock, because dusk moves by nearly two hours across the year and the programme does not. Tonight dusk is 20:16.
19:01
Every outside light on the werf, including the kitchen. From here on, the only white light anyone carries is a mistake.
19:31
Eaten in the last of the light, which is also the first twenty minutes of your adaptation.
20:16
The sun is eighteen degrees below the horizon and the sky is as dark as it will get tonight. Your eyes are about two-thirds of the way there.
20:41
No instrument. This is when the Milky Way stops being a band and starts having structure, and when most people first see the Coalsack as a hole rather than a gap.
21:26
Two or three objects, not twenty. A guide who shows you eleven things in an hour has shown you nothing.
23:16
The galactic centre rises past the ridge to the west-southwest, and the brightest part of the sky is unobstructed until dawn.
The coordinates are in the footer and the meter reading is at the top of this page. Everything between them — the star count, the limiting magnitude, the hour dark begins, how far the galactic centre climbs — was computed from those numbers while this page was built. If you know this sky, you will know whether we are telling the truth about it.
The sky, by dateRooms and the instrumentEnquire about a night