Bortle class 1
The scale stops before we do.
The Bortle scale runs from 9, an inner city, to 1, a sky with no measurable artificial contribution. There is no class 0. If there were, the argument for building here would be easier to make.
- 1
- Bortle class
- 355 mm
- primary mirror
- 21.9 mag
- measured sky brightness, per square arcsecond
A 355 mm reflector, and a person who knows how to point it.
The dome sits four hundred metres from the rooms, far enough that nobody walks past it with a phone. Inside is a 355 mm Newtonian on an equatorial mount, and outside are two smaller instruments guests can take without asking.
Sessions run from full dark until roughly two, every clear night, which is most of them. There is no charge and no sign-up sheet. You walk out and someone is there.
Resident astronomer since 2019
Dr. Ines Marchetti
Formerly of the Cerro Paranal support staff. Will happily spend an hour on a single globular cluster and considers this a reasonable use of an evening.
The season, month by month
| Month | Dark hours | Low | New moon | Overhead |
|---|---|---|---|---|
| January | 6.1 | +8°C | 6 – 13 | Orion low and inverted; Large Magellanic Cloud high |
| February | 6.8 | +6°C | 4 – 11 | Canopus at zenith; core returns before dawn |
| March | 7.9 | +3°C | 6 – 13 | Eta Carinae nebula; both Magellanic Clouds |
| April | 9.2 | 0°C | 4 – 11 | Galactic core clears the ridge by 03:00 |
| May | 10.4 | -4°C | 3 – 10 | Omega Centauri; core through the Zenith skylight |
| June | 11.1 | -7°C | 2 – 9 | Core at its highest; zodiacal light after dusk |
| July | 10.9 | -8°C | 1 – 8, 30 | Sagittarius overhead all night; best of the year |
| August | 9.8 | -5°C | 28 – 4 | Core setting by 02:00; Jupiter season begins |
| September | 8.5 | -1°C | 26 – 3 | Zodiacal light before dawn; 47 Tucanae |
| October | 7.4 | +2°C | 25 – 2 | Small Magellanic Cloud high; core gone by midnight |
| November | 6.5 | +5°C | 24 – 1 | Fornax cluster; the quietest month |
| December | 5.9 | +8°C | 23 – 30 | Shortest nights; Orion returns after midnight |