THE SOUTHWORTH PLANETARIUM

70 Falmouth Street      Portland, Maine 04103

(207) 780-4249      usm.maine.edu/planet

43.6667° N    70.2667° W  Altitude:  10 feet below sea level Founded January 1970

2021-2022: CXXIII

"There are nights when the wolves are silent and only the moon howls."

-George Carlin

THE DAILY ASTRONOMER

Thursday, May 12, 2022

More Lunar Eclipse Questions

Well, yes, we have been somewhat lunar eclipse focused -obsessed- this week.  As we are due to experience a total lunar eclipse in about eighty hours, our fixation is wholly understandable.    Today, we answer the latest lunar eclipse questions we've recently received.  

"I HEARD IT MIGHT BEEN RAINY ON SUNDAY NIGHT.    HOW WILL BE KNOW IF YOUR VIEWING EVENT IS CANCELLED?"   -F.S.

Take it from Odin, weather is a tricky business. So, too, is weather prediction.   As of now, the weather is forecast to be inclement on Sunday.   That prediction could well change, weather being so changeable.   In fact, the phrase "If you don't like the weather, wait a minute," isn't just a New England adage.  It applies everywhere except Hawaii and Venus.       That having been said, we will make a decision about Sunday's event by or before noon-time on Sunday.   If necessary, we'll send a cancellation announcement to the DA list and will post it on our web-site.    

"IS IT TRUE THAT WE'LL HAVE TO WAIT UNTIL 2025 TO SEE THE NEXT TOTAL LUNAR ECLIPSE?"    -R.B.

Here in New England, we will be able to watch the first phases of the November 8, 2022 total lunar eclipse.   The moon will set here before the eclipse ends.    However, the next total lunar eclipse won't occur until March 14, 2025!      Fortunately, we'll see all of that lunar eclipse.   Another total lunar eclipse occurs on September 7, 2025.  However, that eclipse won't be visible to us.    So, yes, after Sunday, we'll have to wait for almost three years until we can watch another entire lunar eclipse.

IMPORTANT NOTE:  The lunar eclipse associated with the April 8, 2024 solar eclipse occurs on March 25, 2024.  That eclipse will only be penumbral, meaning that the moon will only move through the outer part of Earth's shadow.  Such eclipses are hardly noticeable.

"COULD YOU EXPLAIN AGAIN HOW I COULD USE THE SAROS TO PREDICT FUTURE LUNAR ECLIPSES?"   -R.King
Yes.   The Saros refers to the cycle of lunar eclipses within the same series.  Successive eclipses in a given Saros Cycle are separated by 18 years, 11 days and 8 hours.   For instance, Sunday's lunar eclipse is part of the Saros Cycle 131.    The Saros cycle duration enables us to predict with a fair degree of certainty the dates of the next few successive lunar eclipses within this cycle.          Let's try.

We assume that the next Saros 131 lunar eclipse will occur around May 26, 2040, which is 18 years and 11 days later.    The actual date:     May 26, 2040

The date of the next Saros 131 lunar eclipse?    June 6, 2058

The following Saros 131 lunar eclipse:  June 17, 2076

The Saros Cycle duration is 18 years, 11 days and 8 HOURS, so at times, the dates between successive eclipses won't be precisely 18 days and 11 hours.

Also, one cannot use this method forever as Saros Cycles are of finite duration which begin and end as a series of penumbral eclipses.   For instance, the Saros 131 lunar eclipse series began on May 10, 1427 and will end on July 27, 2707.      

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