| Geyser | 1999-12-17 |
|---|---|
| Grand | 0441 E, 1638 E |
| Great Fountain | 1051 E, 1917 E |
| Hillside-West Thumb | 0957 |
| Values for Old Faithful Area | 1999-12-17 |
|---|---|
| Astronomical Twilight Begin | 06:08 |
| Nautical Twilight Begin | 06:43 |
| Civil Twilight Begin | 07:20 |
| Sunrise | 07:53 |
| Sunset | 16:44 |
| Civil Twilight End | 17:18 |
| Nautical Twilight End | 17:54 |
| Astronomical Twilight End | 18:30 |
| Moon Illumination | 63.51% |