Tuesday, December 21, 2010

Eclipses and Perfect Rise/Sets

Boot Key Harbor, Marathon, FL
34 42.54 N 081 05.58 W

I wrote once before about perfect moonrises -- the time when one gets to see the moon rise and the sun set in perfect synchronism.   It is a very rare thing to be able to see it.  Yesterday,  on the eve of an eclipse, I thought I've have a try.

The two pictures below were taken almost simultaneously.  One looks east towards the rising moon and the other west toward the setting sun.  Both are a few degrees above the horizon so the rise/set was less than perfect. 

Indeed, the pictures were shot about 9 hours prior to peak totality.   Mpeoonrise last night was at 17:12 and sunset at 17:40 (+28 minutes difference).  Moonrise this morning was at 7:18 and sunrise at 7:04 (-14 minutes difference).  The moon was ahead of the sun last night and behind this morning.  Sometime in the night, the difference would have been zero.  At that moment, people at about 20 degrees east longitude would have been in position to see the sun rise and moon set in perfect synchronism.

What is your own chance of seeing a perfect rise/set; let's say perfect within 1 degree.     Each 28 days there is a full moon with the time difference zero.  Two lines of longitude, 180 degrees apart, will be in position to see it.  One will see a sunrise/moonset and the other a sunset/moonrise.  Assume that it's cloudy 50% of the time, then your chance of seeing it is 2*360*28/2*365 = once every 28 years.   Like I said, pretty rare.

Libby and I got up at 0300 to see the totality.  The moon was a beautiful orange color.  I tried to photograph it, but I couldn't  (night photography from the deck of a moving boat is almost impossible.)  The picture below comes from Wikepedia.

By the way, I added a new cruising blog link to Traumerei.  That belongs to our friends George and Carol who are moored only 100 feet away.  George did manage to get a picture last night at 0100.  Hat's off to you George, you're a better photographer than I.

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