| Geyser | 1999-12-20 |
|---|---|
| Grand | 0441 E, 1502 E |
| Great Fountain | 0138 E, 1048 E, 2203 E |
| Values for Old Faithful Area | 1999-12-20 |
|---|---|
| Astronomical Twilight Begin | 06:10 |
| Nautical Twilight Begin | 06:45 |
| Civil Twilight Begin | 07:22 |
| Sunrise | 07:55 |
| Sunset | 16:45 |
| Civil Twilight End | 17:19 |
| Nautical Twilight End | 17:56 |
| Astronomical Twilight End | 18:31 |
| Moon Illumination | 91.13% |