Places · Observatory
LIGO Livingston
The southern arm of LIGO, 3,000 km from Hanford. The gap between them is what fixes where on the sky a merger happened.
- Where
- Louisiana, United States
- Coordinates
- 30.56°N 90.77°W
- Since
- 2015
- On the map
- Show me
- More
- ligo.caltech.edu
The sky from here
This is a zone 6 sky — bright suburban on the nine-grade scale, Bortle 6–7, reaching roughly magnitude 4.7–5.5 unaided. The sky within thirty degrees of the horizon glows greyish white. Only the brighter constellations survive.
That grade puts 37 of the catalogue within easy reach of 10×50 binoculars and 37 within a 130mm — 9 of them need no instrument at all. Genuinely dark sky — zone 2 or darker — starts about 171 km south.
There is no season here in which the sky fails to get properly dark — the Sun clears eighteen degrees below the horizon on all 365 nights.
The centre of the galaxy reaches 30° at its highest, which puts the brightest part of the Milky Way clear of the horizon murk without ever being overhead. Of the 110 Messier objects, 4 never set from here and every one of them rises at some point in the year.
Of everything in the catalogue, Triangulum Galaxy, Ring Nebula and Hercules Cluster are the best served here, climbing to within a few degrees of straight up — an object at the zenith is being seen through the least air it will ever be seen through, and the difference against the same object low in the south is not subtle.
Bode's Galaxy and Cigar Galaxy never set from this latitude, so they are available on any clear night of the year rather than for one season of it.
Read at 30.56°N 90.77°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
Nearby
Questions
What part of the sky never rises at LIGO Livingston?
Everything south of declination −59°. From 30.6°N that is a cap 31° in radius centred on the south celestial pole, which is 6.9% of the whole celestial sphere. That part of the sky is not merely a winter object or a difficult one; it is geometrically unavailable from this latitude. The equivalent cap around the north celestial pole is the compensation, and it never sets.
How many hours of true darkness does LIGO Livingston get?
From about 6 hours 37 minutes at the thin end of the year, near 21 June, up to 10 hours 58 minutes around 21 December. Astronomical darkness is the Sun more than eighteen degrees below the horizon, which is a stricter thing than the Sun being down. Unlike sites further from the equator, no part of the year here is written off entirely.
When is the Milky Way best from LIGO Livingston?
Mid-June at its highest, with a workable season either side of it running from about May into September. Because 30.6°N keeps full astronomical darkness all year, the whole of that season is usable, which is not the case for observers much further from the equator, who lose the peak of it to summer twilight.
How far is LIGO Livingston from the other sites on this map?
The nearest is Johnson Space Center — Mission Control, about 430 km to the west. The nearest other observatory is Green Bank Telescope, 1,330 km to the north-east. Distances are great-circle, so they are what a signal covers rather than what a road does.