Into Earth’s Shadow

The eclipse is coming! Yes, finally, a total lunar eclipse is coming our way.  Haven’t had one visible in our neck of the woods since January 21, 2018.

Details:  Wednesday, May 26th.  For us the penumbral phase of this eclipse starts at 3:46 am.  Partial eclipse begins at 4:45 am.  Totality begins at 6:10 am, with deepest eclipse at 6:19 am.  Totality ends at 6:28 am, while the Moon is setting.

The entire eclipse process from first penumbral contact to moonset is around two hours and forty minutes but the main event, totality, only lasts about 18 minutes this time so be there!

Be where?  Anywhere with a clear view of the southwestern sky and horizon.  The Moon sets as totality is ending, so it could be a very cool sight.  I say could be because as the Moon is in totality and close to the horizon the Sun is about to rise.  The brightening sky might cause an eclipse wash out, or It might be a totally awesome sight (pun intended).

This eclipse is expected to be what has been described as a “blood Moon”, quite red/copper in color.  The reason for a red color – it will be passing through the outer portion of Earth’s dark shadow (umbra), where Earth’s atmospheric refraction effects still exist.  The refractive nature of our atmosphere disperses shorter wavelength light (blue, green), but longer wavelengths get through (yellow, orange, red).  So, at the outer portion of Earth’s dark shadow there is some faint light, mostly reddish, and this causes the blood Moon.

For the uninitiated, here are the basics of lunar eclipses.

Lunar eclipses are perfectly safe to watch without protective filters.

A lunar eclipse occurs when the Moon passes through Earth’s shadow.  Because our Earth has an atmosphere, its shadow is not evenly dark.  There is a ring of light shadow (penumbra) surrounding a dark central shadow (umbra).

A lunar eclipse’s nature is based on where in Earth’s shadow the Moon passes. There are three types of lunar eclipse – penumbral, partial, and total.

-Penumbral eclipses occur when the Moon passes only into Earth’s penumbra (light shadow). They are a challenge see because the penumbral shadow is so faint.

-Partial eclipses occur when the Moon passes into but not all the way into Earth’s dark shadow (umbra).  It looks like a piece of Moon has been sliced away.

-Total eclipses occur when the Moon passes all the way into the umbra.  The totally eclipsed Moon can be charcoal to orange to deep red depending on which part of the umbra it crosses.  A total lunar eclipse also goes through penumbral and partial phases prior to and after totality.

Challenge:  With binoculars look for a faint bluish fringe on the umbra’s edge.  This is from light refracting through Earth’s ozone layer.

Also look around for some brighter stars.  Antares in Scorpius is about 7 degrees southeast (left) of the Moon.

This eclipse also coincides with a lunar perigean full Moon – aka “supermoon”.