Located in Custer County, Idaho, Central Idaho Dark Sky Reserve is a dark sky place. It sits roughly 51 km (32 mi) NW of Sun Valley. It is certified as an International Dark Sky Reserve by DarkSky International.
The Central Idaho Dark Sky Reserve is a 1,416-square-mile (3,670 km2) dark-sky preserve near the Sawtooth National Recreation Area, in the U.S. state of Idaho. It was designated on December 18, 2017, and is the first gold-tier dark sky preserve in the United States. The area was designated by International Dark-Sky Association. The area includes the city of Ketchum, Idaho which was separately designated a "Dark Sky Community" in 2017. Idaho State Highway 75 in the Sawtooth Valley between Redfish Lake and Pettit Lake roughly traverses the reserve's "core areas". Several sky quality meters are installed along State Highway 75 in this area.From the Wikipedia article “Central Idaho Dark Sky Reserve”, licensed under CC BY-SA 4.0.
Sunrise & sunset directions
At Central Idaho Dark Sky Reserve the sunrise point swings a long way through the year: about 56° (NE) at the June solstice and 123° (ESE) in late December. Sunset moves from 305° (NW) in June to 238° (WSW) in December, and the midday sun climbs to 69° in summer but only 23° in winter.
| Date | Sunrise | Azimuth | Sunset | Azimuth | Noon sun | Daylight |
|---|---|---|---|---|---|---|
| March equinox (Mar 20) | 7:43 AM | 90° E | 7:52 PM | 271° W | 46° | 12h 09m |
| June solstice (Jun 21) | 5:57 AM | 56° NE | 9:26 PM | 305° NW | 69° | 15h 29m |
| September equinox (Sep 22) | 7:27 AM | 89° E | 7:38 PM | 271° W | 46° | 12h 11m |
| December solstice (Dec 21) | 8:12 AM | 123° ESE | 5:05 PM | 238° WSW | 23° | 8h 53m |
Azimuth is measured clockwise from true north (90° = east, 270° = west). Computed for 2026; values change by less than a degree from year to year.
Golden hour & blue hour by month
Certified dark sky places offer protected night skies — plan around the new moon and the Milky Way core season.
| Month (15th) | Blue hour starts | Sunrise | Golden hour ends | Golden hour starts | Sunset | Blue hour ends | Daylight |
|---|---|---|---|---|---|---|---|
| January | 7:39 AM | 8:11 AM | 8:57 AM | 4:42 PM | 5:27 PM | 5:59 PM | 9h 16m |
| February | 7:10 AM | 7:39 AM | 8:20 AM | 5:29 PM | 6:09 PM | 6:39 PM | 10h 30m |
| March | 7:24 AM | 7:52 AM | 8:31 AM | 7:08 PM | 7:46 PM | 8:14 PM | 11h 53m |
| April | 6:27 AM | 6:57 AM | 7:35 AM | 7:44 PM | 8:23 PM | 8:53 PM | 13h 27m |
| May | 5:41 AM | 6:14 AM | 6:56 AM | 8:17 PM | 8:59 PM | 9:32 PM | 14h 45m |
| June | 5:20 AM | 5:57 AM | 6:41 AM | 8:40 PM | 9:25 PM | 10:01 PM | 15h 28m |
| July | 5:36 AM | 6:11 AM | 6:54 AM | 8:38 PM | 9:21 PM | 9:56 PM | 15h 10m |
| August | 6:13 AM | 6:44 AM | 7:24 AM | 8:06 PM | 8:45 PM | 9:17 PM | 14h 01m |
| September | 6:50 AM | 7:19 AM | 7:57 AM | 7:14 PM | 7:52 PM | 8:21 PM | 12h 32m |
| October | 7:25 AM | 7:54 AM | 8:34 AM | 6:18 PM | 6:57 PM | 7:26 PM | 11h 02m |
| November | 7:04 AM | 7:35 AM | 8:19 AM | 4:31 PM | 5:14 PM | 5:46 PM | 9h 39m |
| December | 7:35 AM | 8:08 AM | 8:55 AM | 4:15 PM | 5:03 PM | 5:36 PM | 8h 55m |
Local time (America/Boise), including daylight saving time. Golden hour runs from about −4° to +6° solar altitude, so the morning golden hour begins during blue hour, before sunrise.
Milky Way & night sky
From Central Idaho Dark Sky Reserve, the Milky Way core is visible in a dark sky from March through September. June gives the longest window (about 3.7 hours on a moonless night), and the core peaks around 17° above the southern horizon. Our light-pollution model puts the sky at about Bortle 1 (excellent dark-sky site), which is excellent for astrophotography.
| Month | Core visible (15th) | Hours | Max altitude | Direction |
|---|---|---|---|---|
| January | Below 10° in darkness | — | -4° | — |
| February | Below 10° in darkness | — | 8° | — |
| March | 5:32 AM – 6:12 AM | 0.7 | 14° | SSE → SSE |
| April | 3:28 AM – 5:08 AM | 1.7 | 16° | SSE → S |
| May | 1:33 AM – 4:03 AM | 2.5 | 17° | SSE → S |
| June | 11:49 PM – 3:29 AM | 3.7 | 17° | SSE → SSW |
| July | 11:35 PM – 2:05 AM | 2.5 | 17° | S → SSW |
| August | 10:37 PM – 12:07 AM | 1.5 | 16° | S → SSW |
| September | 9:30 PM – 10:00 PM | 0.5 | 13° | SSW → SSW |
| October | Below 10° in darkness | — | 8° | — |
| November | Below 10° in darkness | — | -2° | — |
| December | Below 10° in darkness | — | -20° | — |
Window when the galactic core is at least 10° high during astronomical darkness on the 15th of each month. Pick nights within a few days of the new moon. Plan exact nights with the Milky Way planner.
Estimated sky darkness: 1 Bortle 1 — Excellent dark-sky site. The Milky Way casts faint shadows; zodiacal light and airglow are obvious. Modeled zenith brightness ≈ 21.91 mag/arcsec². Aurora needs roughly Kp 6.0+ to show low on the northern horizon here.
Weather & best season
Long-term NASA satellite data for this area show July as the clearest month (about 34% average cloud cover) and March as the cloudiest (70%). July is the warmest month and January the coldest, which matters for gear, snow access and how long batteries last at night.
Average cloud cover (%)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| High °F | 36 | 46 | 60 | 71 | 82 | 89 | 95 | 91 | 88 | 79 | 63 | 44 |
| Low °F | -28 | -22 | -12 | -5 | 15 | 22 | 31 | 31 | 20 | -3 | -23 | -25 |
| Precip. (in) | 1.9 | 1.8 | 2.0 | 1.8 | 1.9 | 1.7 | 0.7 | 0.7 | 1.2 | 1.4 | 1.8 | 2.4 |
Monthly climatology for the surrounding 1° grid cell from NASA POWER (MERRA-2). Mountain sites can be colder and cloudier than the cell average.
Photography tips for this dark sky place
- Use the Milky Way table to find months and hours when the core is above the horizon.
- Use red light only and keep it pointed down to protect others' night vision.
- Set focus on a bright star with live-view magnification, then tape the focus ring.
- Use the NPF rule below to choose the longest exposure before stars trail.
- Scout in daylight if you plan to shoot at night or before sunrise.
Season: Milky Way core season runs roughly March to October; winter offers long nights and bright winter constellations.
Suggested gear: Fast wide lens (f/1.4–f/2.8), Sturdy tripod, Red headlamp, Intervalometer. Work out exposures with the depth of field, ND filter and NPF rule calculators.
Nearby photo spots
Other locations within 40 km of Central Idaho Dark Sky Reserve, closest first.
Hot Spring
Mountain Peak
Mountain Peak
Lake
Mountain Peak
Mountain Peak
Mountain Peak
Mountain Peak
Mountain PeakCampgrounds nearby (Recreation.gov)
- Pettit Lake Campground3.4 km (2.1 mi) · reservable
- Alturas Lake Picnic Area (Id)8.4 km (5.2 mi) · reservable
- Smokey Bear Campground9.1 km (5.7 mi) · reservable
- North Shore Campground9.4 km (5.8 mi) · reservable
- Alturas Lake Inlet11.8 km (7.3 mi) · reservable
FAQ
When is the best time to photograph Central Idaho Dark Sky Reserve?
What time is golden hour at Central Idaho Dark Sky Reserve?
Where does the sun rise and set at Central Idaho Dark Sky Reserve?
Can you see the Milky Way from Central Idaho Dark Sky Reserve?
Do you need a permit to photograph at Central Idaho Dark Sky Reserve?
How far is Central Idaho Dark Sky Reserve from Sun Valley?
Sources
Location data: DarkSky International (via Wikidata), Wikipedia. Sun, moon and Milky Way times are computed by LWPhoto Atlas for 2026. Climate: NASA POWER. Sky darkness is a population-based estimate (Walker's law), not a measurement. See data sources & licenses.