During the July full moon I returned to the ghost town of New Idria. For an excellent background and vintage photos of this historic quicksilver mining town, have a look at the Three Rocks Research site. Seasoned night photographers are familiar with how to calculate sunset and moonrise times. An additional factor that can make a big difference in planning a night photography adventure is the moon altitude. The moon altitude is simply how high the moon is above the horizon, expressed in degrees. The horizon is zero degrees, and straight overhead is 90 degrees. The azimuth is the angle of the moon along the horizon -- zero degrees is North, 180 degrees is South, 90 degrees is East, and 180 degrees is West. The U.S. Naval Observatory (USNO) has an excellent sun/moon data calculator, and also a sun/moon altitude and azimuth calculator.
Let's take a look at the sun/moon data for July 4th with some commentary on how to utilize the numbers:
- Sunset: 8:39 p.m. -- we arrived at the location a few hours before sunset to scout our shots in the daytime.
- End civil twilight: 9:00 p.m. -- time to get your first shot ready to go, shooting can typically begin within 20 minutes of this time.
- Moonrise: 6:48 p.m. -- shooting 3 nights before the full moon means the moon will already be up when the sun goes down.
- Moon transit: 11:29 p.m. -- the moon is approximately half way through its arc across the sky.
- Moonset: 4:10 a.m. on the following day -- important for planning, especially if the moon will drop behind any mountains before this moonset time.
- Moon phase: waxing gibbous with 94% of the moon illuminated -- plenty of light for night photography, but exposures will be slightly longer than when full.
Last September's visit to New Idria was 2 nights before the full moon. The moon was high overhead during optimum shooting hours, with an altitude between 31-45 degrees. (In the Northern Hemisphere, the full moon typically reaches its highest altitude around the time of the Winter Solstice).
The July 2009 full moon had a relatively low altitude. The lower altitude of the moon creates a more directional, harder quality of light than when the moon is high in the sky. Below is a chart that shows the moon altitude during last week's shoot on July 4th:
By a little after 1:15 a.m. the moon was gone behind the ridge. This schedule still allowed a solid 4 hours of night photography. Driving out of the valley into more open territory, the moon appeared again for another hour or so, and then disappeared for the night. Photographing the same location with the moon at a very different place in the sky really helped me better understand just how much the moon altitude effects the quality of light. I hope this article will be helpful in planning your next full moon photography adventure. Enjoy the night photos of New Idria. Many thanks to Steve and Riki for making the trip!