3.4 usable nights
2–4 in the middle half of years · 1.2 typically near a dark moon.
344 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Johnson City
September: 11.5 usable nights on average. Use this seasonal climate baseline to choose a month, then use the live forecast to choose a night.
Site darkness · modelled, not measured
Bright skyBortle classes describe observed sky conditions; this brightness model does not establish a measured Bortle class.19.5–20.2 mag/arcsec²
The short answer
September has been strongest.
It averages 11.5 usable nights, versus 3.4 in January. A typical September lands between 8 and 16 usable nights.
Record2005–2024 · 20 complete years
Usable nightAt least 3 astronomical-dark hours and NASA POWER nighttime cloud ≤30%
Dark-moon nightUsable night with ≤25% illumination at local solar midnight
ResolutionCERES SYN1deg 1° cloud grid; regional climate, not a campsite guarantee
Seasonal fingerprint
Usable nights by month
Month by month
3.6 usable nights
2–4 in the middle half of years · 1.0 typically near a dark moon.
289 astronomical-dark hours in an average month
5.1 usable nights
4–7 in the middle half of years · 1.4 typically near a dark moon.
283 astronomical-dark hours in an average month
6.4 usable nights
4–7 in the middle half of years · 2.4 typically near a dark moon.
240 astronomical-dark hours in an average month
5.8 usable nights
4–6 in the middle half of years · 1.9 typically near a dark moon.
193 astronomical-dark hours in an average month
5.8 usable nights
5–7 in the middle half of years · 2.0 typically near a dark moon.
180 astronomical-dark hours in an average month
5.8 usable nights
4–8 in the middle half of years · 1.4 typically near a dark moon.
186 astronomical-dark hours in an average month
7.8 usable nights
6–10 in the middle half of years · 3.0 typically near a dark moon.
233 astronomical-dark hours in an average month
11.5 usable nights
8–16 in the middle half of years · 4.0 typically near a dark moon.
252 astronomical-dark hours in an average month
11.2 usable nights
8–14 in the middle half of years · 4.4 typically near a dark moon.
310 astronomical-dark hours in an average month
8.4 usable nights
7–10 in the middle half of years · 2.5 typically near a dark moon.
328 astronomical-dark hours in an average month
3.8 usable nights
2–5 in the middle half of years · 1.1 typically near a dark moon.
361 astronomical-dark hours in an average month
Use the baseline honestly
Climate chooses the month. Forecasts choose the night.
The cloud product is a roughly 1° regional grid. It can reveal seasonality, but it cannot know a mountain ridge, valley fog pocket, locked gate, smoke event or the exact sky you will get.
Source: NASA POWER daily data, parameter CLOUD_AMT_NIGHT from the CERES SYN1deg cloud product. GoodSeeing calculates astronomical darkness and lunar illumination independently for each place.