DC REGIONAL OPPORTUNITY TO SHOOT THE MOON IN APRIL 2019
By John Krout
The full moons of March and April usually rise close to the US Capitol dome as seen from the west. But you must know when to look and where to stand. Here is a bit of info on how you can research the details and make plans.
First, when is the moon full? The US Naval Observatory (USNO) offers a Web based interactive system for finding that information for an entire year. Here is the URL: https://aa.usno.navy.mil/data/docs/MoonPhase.php
Once you know the dates of the full moon (April 19), you can use another part of the USNO site to determine exactly where and when the moon rises, and its path through the sky. The URL is: https://aa.usno.navy.mil/data/docs/AltAz.php
The key for using the table of info produced using that URL is to understand how the USNO and astronomers describe the position in the sky of the moon and other objects. They use a coordinate system, but that system is based on compass directions called azimuth and altitude. Here is how it works.
First, the word azimuth means position on the compass. The range is 0-degrees to 359-degrees, where 0-degrees is north, 90-degrees is east, and so forth.
Second, the word altitude means position above the horizon, also measured in degrees. The range is from 0-degrees, which means on the horizon, and 90-degrees, which means directly overhead.
Neither azimuth nor altitude are absolute. Both depend on where you stand. Also the time of day depends on where you stand. So part of the input to the USNO Web page is the city and state where you stand.
The Washington Monument, the US Capitol dome is due east, which means an azimuth of 90-degrees. Any azimuth of the moon just a bit less than 90-degrees means it will show up to the left of the US Capitol dome as seen from the Washington Monument hill. Any moon azimuth greater than 90-degrees means it will show up to the right of the US Capitol dome as seen from the Washington Monument hill.
About 25 years ago I figured out that the azimuth from Freedom Plaza, at 14th Street and Pennsylvania NW, looking southeast along Pennsylvania to the US Capitol dome, is 110-degrees. Any azimuth of the full moon just a bit less than 110-degrees means the moon will show up just to the left of the US Capitol dome as seen from Freedom Plaza. Any azimuth of the full moon that is just a bit more than 110-degrees means that the moon will show up just to the right of the US Capitol dome as seen from Freedom Plaza.
Freedom Plaza is convenient because it is raised several feet above street level. You can stand on it without risk of being hit by a vehicle. Passing buses and cars do not block the view to the east.
Here is a portion the table from the USNO site for the position of the full moon in 10-minute intervals on Friday April 19, 2019 in Washington DC:
Astronomical Applications Dept.
U.S. Naval Observatory
Washington, DC 20392-5420
WASHINGTON, DISTRICT OF COLUMBIA
W 77 02, N38 53
Altitude and Azimuth of the Moon
Apr 19, 2019
Eastern Daylight Time
Altitude Azimuth Fraction
(E of N) Illuminated
20:10 -1.3 101.7 0.99
20:20 0.9 103.2 0.99
20:30 2.6 104.8 0.99
20:40 4.3 106.3 0.99
20:50 6.0 107.9 0.99
21:00 7.8 109.6 0.99
I shot the example photo on April 6, 2012 while standing on Freedom Plaza. The moon was at 109-degrees azimuth, just to the left of the dome, and about 4-degrees altitude.
By comparison, the April 19, 2019 opportunity is not so ideal. The moon will reach 109-degrees azimuth at about 8:58 PM and will be almost twice as high above the horizon, about 7.5-degrees. It will be above the top of the dome.
The April 19 opportunity might work better if the viewpoint is moved From Freedom Plaza, on the north side of Pennsylvania Avenue, to the south side of Pennsylvania Avenue. On that side, the azimuth to the Capitol dome is a bit less than 110 degrees, and the moon will be at an appropriate altitude between 8:40 PM and roughly 8:45 PM.
On the south side of Pennsylvania Avenue, you must stand on the sidewalk, below the level of Freedom Plaza. Passing cars and buses may sometimes block your view. You will have to use a telephoto lens and won’t be able to include much of the street scene. Simplicity is often good in photos.
In the example photo, the low altitude of the moon means that the moon is seen through over 1,000 miles of atmosphere. Atmospheric refraction of sunlight chances the color of the moon, and atmospheric scattering reduces the brightness of the moon compared to when it is high overhead.
Nonetheless, the moon is much brighter than the street scene. The choice is to capture details in the Moon and underexpose the local scene or overexpose the moon and capture details in the local scene. I did the latter and used Photoshop to reduce the moon’s brightness to bring out some detail.
Incidentally, the Fraction Illuminated column in the table indicates that 99% of the face of the moon will be illuminated on April 19. The difference of 1% is not going to be noticed by most who see photos of the moon. The example photo was also shot when the face was 99% illuminated.
Of course, the weather could intervene. Recent weather in 2019 has been rather volatile.
About the author:
John Krout is a member of NVPS. He has been shooting photos with an SLR since 1970. He was employed as a summer intern photographer by the National Park Service in 1974 during college. Also, during college, he shot photos of and wrote reviews about rock concerts in Boston for his college newspaper, and also shot photos of concerts n DC, Charlottesville and Richmond. One of his recent efforts has been to shoot photos of aircraft silhouetted in front of the full moon. For most of his working life he was a C and C++ software developer for major computer systems. He works now as a tech writer for a major maker of automated fingerprint identification hardware. He lives in Arlington VA.