Two limits apply and you always get the smaller. The sky here has a ceiling of magnitude 6.43, 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 | 11 |
| 3 | 4.20 | 229 |
| 7 | 5.20 | 808 |
| 13 | 6.00 | 2,049 |
| 20 | 6.43 | 3,274 |
| 25 and after | 6.43 | 3,274 |
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 3 is what is over this property; Bortle 9 is a city centre, and the difference between them tonight is a factor of 31.5.
Bortle 1
3,603
22.00 mag/arcsec² · limit 6.62
Bortle 2
3,525
21.85 mag/arcsec² · limit 6.56
Bortle 3
3,274
21.60 mag/arcsec² · limit 6.43 · here
Bortle 4
2,690
21.30 mag/arcsec² · limit 6.28
Bortle 6
584
19.25 mag/arcsec² · limit 4.96
Bortle 8
184
18.00 mag/arcsec² · limit 3.97
Bortle 9
104
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 20:34.
19:04
Everything electric in the bothy is out from here, including anything with a screen. There is a red head torch on a hook by the door and it is the only thing you should be carrying.
19:44
Eleven steps, and then you stop and wait. Most people come back inside after four minutes the first time and understand why they should not have, about a night later.
20:34
The sun is eighteen degrees down. From May to August this line simply does not occur, and the ledger on the sky page marks every night it does not.
21:04
The 15x70s on the mount, and nothing else. The Double Cluster, the Andromeda Galaxy, and whatever is crossing the break.
22:04
Two objects. The shelter is the reason this happens at all — an unsheltered session in a Galloway glen in February ends in about twenty minutes whatever anyone intended.
00:04
Which is the part everybody remembers, and the part no photograph of a sky has ever managed to convey.
At this latitude the sun does not get eighteen degrees below the horizon between early May and early August, so there is no astronomical darkness at all — not less of it, none. The exact count is on the sky page, computed for the year rather than quoted from memory, and it is the first thing anyone thinking of coming in June should read.
The sky, by dateRooms and the instrumentEnquire about a night