Located in Denver County, Colorado, Rocky Mountain Arsenal National Wildlife Refuge is a national wildlife refuge. It sits roughly 6.6 km (4.1 mi) E of Derby.
The Rocky Mountain Arsenal National Wildlife Refuge is a 15,988-acre (24.981 sq mi) National Wildlife Refuge located adjacent to Denver and Commerce City, Colorado, in the United States. It is approximately 8 miles (13 km) northeast of downtown Denver. The refuge is on the grounds of the former Rocky Mountain Arsenal, a United States Army chemical weapons manufacturing facility. The site was designated a national wildlife refuge in 1992 by the United States Congress, and underwent a costly environmental cleanup in order to remove pollutants. The refuge is managed by the United States Fish and Wildlife Service. More than 330 species of wildlife inhabit the refuge, including raptors, deer, raccoons, coyotes, white pelicans, black-footed ferrets, black-tailed prairie dogs, and bison.From the Wikipedia article “Rocky Mountain Arsenal National Wildlife Refuge”, licensed under CC BY-SA 4.0.
Sunrise & sunset directions
At Rocky Mountain Arsenal National Wildlife Refuge the sunrise point swings a long way through the year: about 58° (ENE) at the June solstice and 121° (ESE) in late December. Sunset moves from 302° (WNW) in June to 240° (WSW) in December, and the midday sun climbs to 74° in summer but only 27° in winter.
| Date | Sunrise | Azimuth | Sunset | Azimuth | Noon sun | Daylight |
|---|---|---|---|---|---|---|
| March equinox (Mar 20) | 7:04 AM | 90° E | 7:12 PM | 271° W | 50° | 12h 08m |
| June solstice (Jun 21) | 5:32 AM | 58° ENE | 8:32 PM | 302° WNW | 74° | 15h 00m |
| September equinox (Sep 22) | 6:48 AM | 89° E | 6:58 PM | 271° W | 50° | 12h 10m |
| December solstice (Dec 21) | 7:18 AM | 121° ESE | 4:39 PM | 240° WSW | 27° | 9h 21m |
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
Wildlife is most active in the first and last two hours of daylight — exactly when the light is warmest.
| Month (15th) | Blue hour starts | Sunrise | Golden hour ends | Golden hour starts | Sunset | Blue hour ends | Daylight |
|---|---|---|---|---|---|---|---|
| January | 6:50 AM | 7:20 AM | 8:01 AM | 4:18 PM | 4:59 PM | 5:29 PM | 9h 40m |
| February | 6:25 AM | 6:53 AM | 7:31 AM | 4:58 PM | 5:36 PM | 6:04 PM | 10h 43m |
| March | 6:45 AM | 7:12 AM | 7:47 AM | 6:31 PM | 7:07 PM | 7:33 PM | 11h 55m |
| April | 5:54 AM | 6:22 AM | 6:59 AM | 7:01 PM | 7:38 PM | 8:06 PM | 13h 15m |
| May | 5:15 AM | 5:45 AM | 6:24 AM | 7:29 PM | 8:08 PM | 8:38 PM | 14h 22m |
| June | 4:59 AM | 5:31 AM | 6:12 AM | 7:49 PM | 8:30 PM | 9:03 PM | 14h 59m |
| July | 5:13 AM | 5:44 AM | 6:24 AM | 7:48 PM | 8:28 PM | 8:59 PM | 14h 43m |
| August | 5:43 AM | 6:12 AM | 6:49 AM | 7:20 PM | 7:57 PM | 8:26 PM | 13h 45m |
| September | 6:14 AM | 6:41 AM | 7:17 AM | 6:34 PM | 7:10 PM | 7:37 PM | 12h 29m |
| October | 6:43 AM | 7:10 AM | 7:47 AM | 5:45 PM | 6:21 PM | 6:49 PM | 11h 11m |
| November | 6:16 AM | 6:45 AM | 7:25 AM | 4:05 PM | 4:45 PM | 5:14 PM | 10h 00m |
| December | 6:44 AM | 7:14 AM | 7:57 AM | 3:54 PM | 4:36 PM | 5:07 PM | 9h 22m |
Local time (America/Denver), 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 Rocky Mountain Arsenal National Wildlife Refuge, the Milky Way core is visible in a dark sky from March through September. June gives the longest window (about 4.8 hours on a moonless night), and the core peaks around 21° above the southern horizon. Our light-pollution model puts the sky at about Bortle 7 (suburban / urban transition), so expect visible sky glow; drive away from towns for better results.
| Month | Core visible (15th) | Hours | Max altitude | Direction |
|---|---|---|---|---|
| January | Below 10° in darkness | — | -3° | — |
| February | 5:06 AM – 5:16 AM | 0.2 | 11° | SE → SE |
| March | 4:16 AM – 5:36 AM | 1.3 | 18° | SE → SSE |
| April | 2:14 AM – 4:44 AM | 2.5 | 21° | SE → S |
| May | 12:17 AM – 3:47 AM | 3.5 | 21° | SE → S |
| June | 10:31 PM – 3:21 AM | 4.8 | 21° | SE → SSW |
| July | 10:23 PM – 2:03 AM | 3.7 | 21° | S → SW |
| August | 9:38 PM – 11:58 PM | 2.3 | 21° | S → SW |
| September | 8:41 PM – 10:01 PM | 1.3 | 18° | SSW → SW |
| October | 7:51 PM – 8:01 PM | 0.2 | 12° | SW → SW |
| November | Below 10° in darkness | — | 0° | — |
| December | Below 10° in darkness | — | -19° | — |
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: 7 Bortle 7 — Suburban / urban transition. The whole sky has a grey-white glow; the Milky Way is invisible to the eye. Modeled zenith brightness ≈ 18.83 mag/arcsec². Aurora needs roughly Kp 7.5+ to show low on the northern horizon here.
Weather & best season
Long-term NASA satellite data for this area show September as the clearest month (about 38% average cloud cover) and February as the cloudiest (57%). July is the warmest month and December 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 | 70 | 73 | 79 | 87 | 95 | 103 | 103 | 102 | 97 | 86 | 77 | 67 |
| Low °F | -2 | -9 | 0 | 10 | 21 | 35 | 49 | 43 | 28 | 8 | -1 | -6 |
| Precip. (in) | 0.5 | 0.6 | 1.1 | 1.8 | 2.3 | 1.9 | 2.4 | 2.2 | 1.3 | 1.0 | 0.6 | 0.5 |
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 national wildlife refuge
- Migration peaks bring the largest concentrations — see the birding calendar for this state.
- Use auto-loop roads as mobile blinds; animals often tolerate vehicles more than people on foot.
- Stay on designated routes and keep a respectful distance — if an animal changes behavior, you are too close.
- A 400–600 mm lens (or a crop body) is the usual tool for birds.
- Fast shutter speeds (1/2000 s+) freeze wingbeats; raise ISO rather than lose the shot.
- Shoot RAW to keep the most latitude for high-contrast sunrise and sunset scenes.
Season: Spring and autumn migration are the highlights; winter brings waterfowl to many southern refuges.
Suggested gear: Telephoto lens (400 mm+), Bean bag for car window, Binoculars. Work out exposures with the depth of field, ND filter and NPF rule calculators.
Permits, drones & access
Drones: Launching or landing drones on National Wildlife Refuge lands generally requires a special use permit from the refuge manager, and wildlife disturbance rules apply everywhere.
Nearby photo spots
Other locations within 40 km of Rocky Mountain Arsenal National Wildlife Refuge, closest first.
State Park
Botanical Garden
Botanical Garden
Botanical Garden
Lake
National Wildlife Refuge
State Park
Botanical Garden
Mountain PeakFAQ
When is the best time to photograph Rocky Mountain Arsenal National Wildlife Refuge?
What time is golden hour at Rocky Mountain Arsenal National Wildlife Refuge?
Where does the sun rise and set at Rocky Mountain Arsenal National Wildlife Refuge?
Can you see the Milky Way from Rocky Mountain Arsenal National Wildlife Refuge?
Do you need a permit to photograph at Rocky Mountain Arsenal National Wildlife Refuge?
How far is Rocky Mountain Arsenal National Wildlife Refuge from Derby?
Sources
Location data: 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.