Lunar Eclipse

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May 16th, time to pick up my old hobby Astronomy again. Finally there was this nice opportunity to spot a lunar eclipse, but instead of only looking at it in the middle of the night I also decided to try to photograph this event. But looking up the exposure times on the net I got intrigued by the cycles of Lunar (and Solar eclipses).

Where I thought it was just pure luck if the Earth would be happen exactly in between the Sun and the Moon (of course I knew that the rotation of the moon around the earth, the 'month', has to do with it), it seems that it has nothing to do with luck at all. You see, the Moon circles around the Earth, but not in the same plane as the Earth circles around the Sun (also called the Eclipta). This is why there is not a lunar eclipse every 29.53059 days (also called the Synodic Month, which is the time between two new moons). The moon passed through the Eclipta every 27.21222 days (also called the Draconic Month). When those two cycles are in sync, which happens every 223 Synodic months or 242 Draconic months, a lunar eclipse can be seen. This period of 18 years 11 days and 8 hours is called the Saros. Because there is an 8 hours difference between eclipses of the same Saros the eclipses will shift about 120 degrees every time. A triple Saros is a period of 54 years and 34 days and produce about the same eclipse at the same location.

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In every Saros there are about 70 to 80 eclipses, a Saros cyclus has a limited lifetime because the two cycles of Synodic and Draconic months don't match up exactly. This means that during a Saros series eclipses will shift either from South to North over the Earth, or from North to South with an average distance of about 350 km. But anyway, after all this complex matter it became clear that predicting Lunar eclipses (and of course also Solar eclipses) isn't that easy at all. The May 16th, 2003 eclipse was one of Saros series 121, a series that will only produce one more total eclipse (on May 26th, 2021).

The diagram on the left shows the times and the path that the Moon follows through Earth's shadow. All times are in UTC so that meant that I needed to add two hours to these times (my hometown is in GMT+2 during D.S.T.). The Moon started to move into Earths Umbra (U1) at 4:02am and for some reason my alarm clock even woke me up a few minutes before. For once it was not cloudy at all, so I grabbed my camera (Minolta 404) and put my 210mm lens on it. For this event I was using a 200 ASA Fujicolor film. (I know, it's not the best one... but this happened to be the film in my camera :). After mounting the camera on a tripod I started to track the event with my eyes. In the first few minutes there was little to see of course so just configured my camera correctly (ie, turn off flasher and set the aperture and exposure times). From my previous errors with photographing the July 11th, 1999 solar eclipse I decided to alternate the settings a bit to have a better chance of making the best picture possible.

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The composition of photos on the right are made at respectively 4:10am, 4:15am and 4:25am, all with an aperture of 8 and an exposure time of 1/125 second. I continued with taking photographs every 5 minutes, but I somehow set the exposure time too short to make the pictures look decent enough. (Also, they might have been nice, but they were not printed by the photoshop and I decided not to print them all). Because the Moon was setting I was not able to follow the progress of the eclipse after 4:43am. The next Lunar eclipse visible in Europe will be on Nov 9th, 2003 and should give much better circumstances to view the event as the Moon will be about at highest point in the sky when the eclipse is full. Totality will only last for 24 minutes though as it's the last eclipse in Saros series 126 that will be a total one.

Disclaimer: Most of the data presented on this page where gathered from Fred Espenaks excellent eclipse resource page. Photos are © by Derick Rethans and can not be used in print or electronic publishing without written permission.

Comments

Neat stuff Mr. Rethans!

However, I am still pissed about the licensing issue stuff! :)

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