11.1 usable nights
8–16 in the middle half of years · 3.4 typically near a dark moon.
341 astronomical-dark hours in an average month
20-year trip-planning baseline
When to plan an observing trip to Santa Maria
August: 26.7 usable nights on average. A regional planning baseline, not a forecast for your trip.
Site darkness · modelled, not measured
Brightened skyBortle classes describe observed sky conditions; this brightness model does not establish a measured Bortle class.19.9–20.6 mag/arcsec²
The short answer
August has been strongest.
It averages 26.7 usable nights, versus 9.5 in December. A typical August lands between 25 and 29 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
11.8 usable nights
7–18 in the middle half of years · 3.9 typically near a dark moon.
288 astronomical-dark hours in an average month
12.6 usable nights
10–16 in the middle half of years · 3.0 typically near a dark moon.
286 astronomical-dark hours in an average month
16.4 usable nights
14–19 in the middle half of years · 5.2 typically near a dark moon.
240 astronomical-dark hours in an average month
19.6 usable nights
15–23 in the middle half of years · 6.5 typically near a dark moon.
200 astronomical-dark hours in an average month
23.2 usable nights
20–27 in the middle half of years · 7.8 typically near a dark moon.
180 astronomical-dark hours in an average month
25.3 usable nights
23–28 in the middle half of years · 8.1 typically near a dark moon.
188 astronomical-dark hours in an average month
26.7 usable nights
25–29 in the middle half of years · 8.8 typically near a dark moon.
240 astronomical-dark hours in an average month
23.6 usable nights
22–26 in the middle half of years · 8.4 typically near a dark moon.
255 astronomical-dark hours in an average month
20.8 usable nights
19–24 in the middle half of years · 7.1 typically near a dark moon.
310 astronomical-dark hours in an average month
15.5 usable nights
14–18 in the middle half of years · 5.1 typically near a dark moon.
327 astronomical-dark hours in an average month
9.5 usable nights
5–12 in the middle half of years · 3.6 typically near a dark moon.
358 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.