Upper Tub (Udon Bowl) is a hot spring in Yukon-Koyukuk Census Area, Alaska. It sits roughly 68 km (42 mi) NW of College.
Sunrise & sunset directions
At Upper Tub (Udon Bowl) the sunrise point swings a long way through the year: about 11° (N) at the June solstice and 157° (SSE) in late December. Sunset moves from 349° (N) in June to 203° (SSW) in December, and the midday sun climbs to 48° in summer but only 1° in winter.
| Date | Sunrise | Azimuth | Sunset | Azimuth | Noon sun | Daylight |
|---|---|---|---|---|---|---|
| March equinox (Mar 20) | 7:56 AM | 89° E | 8:11 PM | 272° W | 25° | 12h 15m |
| June solstice (Jun 21) | 2:45 AM | 11° N | 1:11 AM | 349° N | 48° | 22h 26m |
| September equinox (Sep 22) | 7:39 AM | 88° E | 7:59 PM | 273° W | 25° | 12h 20m |
| December solstice (Dec 21) | 11:13 AM | 157° SSE | 2:36 PM | 203° SSW | 1° | 3h 23m |
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
Steam is most visible on cold mornings; backlight from a low sun makes rising steam glow.
| Month (15th) | Blue hour starts | Sunrise | Golden hour ends | Golden hour starts | Sunset | Blue hour ends | Daylight |
|---|---|---|---|---|---|---|---|
| January | 9:24 AM | 10:38 AM | — | — | 3:33 PM | 4:47 PM | 4h 55m |
| February | 8:03 AM | 8:57 AM | 10:22 AM | 3:59 PM | 5:24 PM | 6:18 PM | 8h 27m |
| March | 7:25 AM | 8:15 AM | 9:22 AM | 6:49 PM | 7:55 PM | 8:45 PM | 11h 41m |
| April | 5:19 AM | 6:18 AM | 7:28 AM | 8:24 PM | 9:33 PM | 10:32 PM | 15h 15m |
| May | — | 4:27 AM | 5:58 AM | 9:47 PM | 11:18 PM | — | 18h 51m |
| June | — | 2:49 AM | 5:10 AM | 10:43 PM | 1:04 AM | — | 22h 15m |
| July | — | 3:50 AM | 5:38 AM | 10:25 PM | 12:14 AM | — | 20h 25m |
| August | 4:29 AM | 5:40 AM | 6:55 AM | 9:06 PM | 10:21 PM | 11:32 PM | 16h 41m |
| September | 6:27 AM | 7:18 AM | 8:23 AM | 7:20 PM | 8:25 PM | 9:16 PM | 13h 07m |
| October | 7:59 AM | 8:50 AM | 10:04 AM | 5:20 PM | 6:34 PM | 7:24 PM | 9h 43m |
| November | 8:32 AM | 9:36 AM | 12:12 PM | 1:10 PM | 3:46 PM | 4:50 PM | 6h 10m |
| December | 9:37 AM | 11:06 AM | — | — | 2:37 PM | 4:06 PM | 3h 31m |
Local time (America/Anchorage), 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
The Milky Way's bright core (in Sagittarius) barely clears the southern horizon at this latitude, so focus on winter Milky Way, aurora or star trails instead.
| Month | Core visible (15th) | Hours | Max altitude | Direction |
|---|---|---|---|---|
| January | Below 10° in darkness | — | -14° | — |
| February | Below 10° in darkness | — | -10° | — |
| March | Below 10° in darkness | — | -10° | — |
| April | Below 10° in darkness | — | -9° | — |
| May | No darkness | — | — | — |
| June | No darkness | — | — | — |
| July | No darkness | — | — | — |
| August | No darkness | — | — | — |
| September | Below 10° in darkness | — | -13° | — |
| October | Below 10° in darkness | — | -12° | — |
| November | Below 10° in darkness | — | -14° | — |
| December | Below 10° in darkness | — | -22° | — |
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 ≈ 21.93 mag/arcsec². Aurora needs roughly Kp 0.0+ to show low on the northern horizon here.
Weather & best season
Long-term NASA satellite data for this area show March as the clearest month (about 46% average cloud cover) and October as the cloudiest (79%). 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 | 35 | 34 | 34 | 64 | 78 | 82 | 83 | 81 | 67 | 59 | 34 | 33 |
| Low °F | -49 | -42 | -43 | -22 | 5 | 25 | 36 | 28 | 14 | -16 | -39 | -45 |
| Precip. (in) | 0.8 | 0.8 | 0.7 | 1.0 | 1.3 | 2.5 | 2.8 | 2.8 | 2.0 | 1.2 | 1.1 | 1.0 |
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 hot spring
- Keep to boardwalks and marked paths — crusts around thermal features can be thin and the water dangerously hot.
- A polarizer brings out the colors of mineral terraces and microbial mats.
- Respect bathers' privacy: ask before including people at soaking pools.
- Wind direction determines where steam drifts; shoot from the upwind side to see the pool.
- Condensation forms quickly on lenses; let gear acclimate and carry a cloth.
- Scout in daylight if you plan to shoot at night or before sunrise.
Season: Winter gives the most dramatic steam; some primitive springs are only accessible in summer.
Suggested gear: Circular polarizer, Lens cloth, Telephoto for distant pools. Work out exposures with the depth of field, ND filter and NPF rule calculators.
Nearby photo spots
Other locations within 25 km of Upper Tub (Udon Bowl), closest first.
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Sources
Location data: OpenStreetMap contributors. 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.