Tuesday, April 8, 2014

Coming Soon To A Sky Near You!

It has been a long time coming, but this next Monday night, 14 April, there will be a total lunar eclipse!  This occurs during the full moon when it passes into the shadow of the Earth - totally safe to observe, unlike a solar eclipse.  You might rightfully ask why there isn't a lunar eclipse every full moon.  It is because its orbit is inclined about 5 degrees to the ecliptic, the sun's apparent path across the sky.  A total lunar eclipse only occurs when the moon is full and is at the ascending or descending nodes, where the moon's path crosses the ecliptic.

While they typically happen a couple times a year, in the Americas, our astronomical fates have not shown us a total lunar eclipse since December of 2010!  The pictures shown here were taken on 21 December of that year, through the thin clouds that came and went.  At left is a partial phase, where the moon was moving towards the lower left into the Earth's shadow.  The right picture was taken during totality - even though entirely in the Earth's shadow, it was still illuminated by light diffused by the Earth's atmosphere.  One analogy I've heard is that the moon is lit up by all the simultaneous sunsets and sunrises around the world.

The only disadvantage of this eclipse is that it occurs very late on a school night (again, Monday night, Tuesday morning).  In Arizona time, the partial phase starts about 11pm, and totality just after Midnight.  Mid-totality is at 12:45 and totality ends about 1:30am.  Again, that is Arizona, Mountain Standard Time...  Central Daylight is 2 hours different (later - mid-totality at 2:45am), and Eastern Daylight 3 hours later (3:45am for mid-totality).  We'll be out hopefully with better conditions than 2010 where these were our best shots.

Ironically, we're in the front row seat for the next 4 (!) lunar eclipses.  At about 6 month intervals, we should be able to observe all of them the next 2 years!  So if you miss this one, there is another in October, though that is on a school night too...

1 comment:

Vilma Anderson said...

Hi guys!
Looking forward to seeing your pictures from this lunar eclipse, we were cloudy and rained out :(