How dark is the sky at Coll?

Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Coll at about 21.95 mag/arcsec², roughly Bortle class 2. That is an approximation derived from satellite data, not a field measurement; it is certified by DarkSky International as an International Dark Sky Community.

How far is Coll from Glasgow?

About 166.1 km in a straight line, heading north-west from Glasgow. Using a 1.3 road-detour factor and staged average speeds that is roughly 215.9 km and 2.7 h of driving — an estimate, not a routed drive time.

When is the next moon-free dark window at Coll?

The next stretch of essentially moon-free dark hours runs Nov 3–15 (13 nights), computed from Moon phase and altitude with Skyfield and JPL DE440s. Cloud cannot be known that far ahead; the live seven-night forecast on this page shows real cloud cover once a window is close.

What is the clearest month at Coll?

Over 2021–2025, April (41%), May (35%), June (29%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 23%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.

United Kingdom · International Dark Sky Community

Stargazing at Coll

How dark this certified sky really is, how far it is from the nearest cities, a live seven-night forecast for the site itself, and the moon-free nights worth planning around. Official DarkSky International page ↗

Sky at the siteBortle ≈ 221.95 mag/arcsec² · 2024 atlas

From Glasgow~2.7 h166.1 km straight-line · head north-west · estimated

Next moon-free windowNov 3–1513 nights · moon geometry only

How dark the sky really is at Coll

Modelled zenith brightness at the site's coordinates is 21.95 mag/arcsec², which maps to roughly Bortle 2 (what each level means). This is an approximation from the 2024 light-pollution atlas, not a field measurement — and it describes the single point DarkSky lists, not the darkest corner of the community.

This is about as dark as the atlas gets: at Bortle 2 the Milky Way casts visible shadows on moonless nights, the zodiacal light is obvious and the faintest deep-sky objects are within reach of modest optics. Your own light — and the Moon — will be the limiting factor, not the site.

Getting to Coll

The nearest cities we publish guides for, with the direction to head and a rough drive estimate.

From Glasgow
head north-west · 166.1 km straight-line · ≈215.9 km by road · ≈2.7 h · weekend trip
From Edinburgh
head west · 221.1 km straight-line · ≈287.4 km by road · ≈3.5 h · weekend trip
From Belfast
head north · 228.4 km straight-line · ≈296.9 km by road · ≈3.6 h · weekend trip

Estimated from straight-line distance x a 1.3 road-detour factor and staged average speeds (40 km/h leaving town, 70 km/h regional, 95 km/h highway). It is a rough guide, not a routed drive time.

The next seven nights at Coll

Loading the live forecast…

Plan the next 90 days at Coll

Moon-free dark windows are astronomy — computable years ahead. Cloud is not: beyond the 16-night forecast nobody knows the weather, and we won't pretend to. What five years of reanalysis can say is how often each month's nights actually stayed clear here.

Nov 3–1513 moon-free nights16% of November nights here stayed clear (2021–2025)
Dec 2–1514 moon-free nights14% of December nights here stayed clear (2021–2025)
Dec 31 – Jan 1314 moon-free nights14% of December nights here stayed clear (2021–2025)

Clear nights by month, 2021–2025

Jan15%
Feb15%
Mar26%
Apr41%
May35%
Jun29%
Jul23%
Aug25%
Sep26%
Oct12%
Nov16%
Dec14%

Clearest months historically: April (41%), May (35%), June (29%); across the year 23% of nights with astronomical darkness stayed clear.

"Clear" = weighted cloud cover (low 0.5 / mid 0.3 / high 0.2) ≤ 20% across the night's astronomical darkness. ERA5 reanalysis via Open-Meteo Archive, 2021–2025 (CC BY 4.0) — historical frequency, not a forecast. Once a window comes within 16 nights, the live forecast above takes over.

Put Coll's dark-sky nights on your calendar

Every month has a stretch of nights when the Moon leaves the dark hours at Coll essentially moon-free. Subscribe once and each window lands in your own calendar, about a year ahead — no account, no email.

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moon & darkness geometry only — cloud can't be known this far out; check the live forecast above when a window gets close

Questions people ask about Coll

How dark is the sky at Coll?: Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Coll at about 21.95 mag/arcsec², roughly Bortle class 2. That is an approximation derived from satellite data, not a field measurement; it is certified by DarkSky International as an International Dark Sky Community.
How far is Coll from Glasgow?: About 166.1 km in a straight line, heading north-west from Glasgow. Using a 1.3 road-detour factor and staged average speeds that is roughly 215.9 km and 2.7 h of driving — an estimate, not a routed drive time.
When is the next moon-free dark window at Coll?: The next stretch of essentially moon-free dark hours runs Nov 3–15 (13 nights), computed from Moon phase and altitude with Skyfield and JPL DE440s. Cloud cannot be known that far ahead; the live seven-night forecast on this page shows real cloud cover once a window is close.
What is the clearest month at Coll?: Over 2021–2025, April (41%), May (35%), June (29%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 23%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.

Place name and coordinates: DarkSky International (reviewed 2026-07-15, data 2026-10-13). Light pollution: David Lorenz, World Atlas 2024 (EOG VIIRS, CC BY 4.0), approximate. Cloud: Open-Meteo.com (CC BY 4.0). Moon and darkness geometry: Skyfield + JPL DE440s, computed locally. Drive times are estimates, not routes.