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| Longs Peak, notch couloir. 3/10/2012 06:44 |
Sometime durring or after Grace and I climbed the Notch Couloir on Longs Peak, I conceived the idea of photographing the peak with the moon setting into the notch. I figured out when and where this might be done using a map, compass, calculator, and an astronomical table. It took hours.
Then I discovered The Photographer's Ephemeris, which will do the same job in a few minutes. There is a free desktop version or, for a modest fee, you can get it on your smart phone (iOS & Android). With it, you can calculate azimuth and altitude to the sun and moon anywhere on earth, any time. You can measure the apparent altitude of terrain features from a given location. You can correct sunrise and sunset times for the apparent altitude of the horizon. It even uses your location to automatically detect your timezone and daylight savings time status. The only thing it hasn't got that I wanted is a table showing the dates of lunar perigee and apogee.
With the help of TPE, I arrived at one nearly ideal point in space-time for the shot:
When: March 10th, 06:40;
Where: N40.282341, W-105.514627, 12200' elevation
It took no convincing for Ethan to accompany me for my appointment with moon and mountain. I left Denver at 01:10 saturday morning and picked up Ethan at a quarter to two. By 05:30 we were standing on the southern summit of Twin Sisters Mountain waiting for the moon to descend. We weren't disappointed.
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