WASHINGTON — Get ready for a rare double feature this weekend in the sky this weekend that will make it an event you won’t want to miss.
Let’s hope for clear skies this Sunday night as we will want to see a rare celestial event that last occurred in 1982 and won’t happen again until 2033 — a supermoon total lunar eclipse. Add to it that this will also be the harvest full moon and the closest full moon of 2015 and you have what I consider to be the skywatching event of 2015.
The harvest full moon is the full moon that occurs closest to the Autumnal Equinox. In days gone by, farmers used the light of the full moon to harvest their crops, according to NASA.
The term “supermoon” has made its way into everyday usage, but it is not an astronomical term. When the moon orbits the Earth each month, it passes a point where it is closest to our planet — perigee — and farthest — apogee. When the full moon occurs within 24 hours of perigee it is a perigee full moon or what is now known as a supermoon.
Because this supermoon is the closest full moon for all of 2015, we will see a full moon 14 percent larger in diameter and 30 percent brighter than the farthest Full Moon of 2015.
In the east, the moon will enter the outer shadow of our planet called the penumbra at 8:11 p.m. EDT. The penumbra is a ghostly shadow that is hard to see but should be visible in binoculars or a telescope. Things get much easier to see when the moon enters the dark umbra shadow of our planet at 9:07 p.m. EDT to start the partial eclipse phase. You will see the dark curvature of our planet projected onto the moon, and as time goes on more and more of the moon gets covered.
At 10:11 p.m. EDT, things get interesting as this is when the total eclipse phase begins — when the full moon is completely immersed in the shadow of our planet.
The halfway point of the eclipse occurs at 10:48 p.m. EDT. No direct sunlight is falling on the full moon in this phase of the eclipse and we should see the characteristic “copper penny” color covering the moon for a wonderfully long 72 minutes!
The copper reddish color that you should see is caused by sunlight passing through the Earth’s atmosphere and being refracted to a reddish color just like we see at sunrise and sunset. If you were an astronaut on the moon, you would see the darkened Earth surrounded by a ring of red light along the circumference of our planet. All of our planet’s sunrises and sunsets would be visible as this reddish colored ring. It is this light that we see on the moon during the totality phase of the eclipse.
The color and its brightness that we view on the totally eclipsed moon can vary due to worldwide atmospheric conditions. The 1992 total lunar eclipse that occurred after Mount Pinatubo erupted in the Philippines in 1991 was so dark as to be nearly invisible in the sky — even in my telescope.
This was due to the amount of aerosols and debris from the volcano’s eruption that were placed high into the Earth’s atmosphere which blocked the passage of sunlight through our atmosphere. Scientists can measure the brightness and color of the totally eclipsed Moon to glean the condition of the Earth’s high atmosphere.
The full moon starts to emerge into sunlight once again partially eclipsed at 11:23 p.m. EDT to 12:27 a.m. EDT. The full moon leaves the outer shadow of our planet at 1:22 a.m. EDT which ends the eclipse.
The best place to see the eclipse is an area that has an unobstructed view of the eastern sky and is free of bright lights. When the moon is in totality phase the stars of fall will appear and we should see the Milky Way nearby.
I hope you can join me at Shenandoah National Park’s Big Meadows as this is an ideal location to see the eclipse.
Binoculars or a small telescope will help your view as you will be able to see the moon and its colors far better than with the unaided eye.
You can take pictures of the eclipse if you have a camera and tripod. A zoom lens is a big help, but almost any camera will capture the Earth’s shadow and the color of totality. You can get more information on the Sky & Telescope site.
The Sky & Telescope site offers more information about the eclipse on its website.
If it is cloudy, you can tune in on the Internet to see the eclipse via NASA starting at 8 p.m. EDT.
Here’s to clear skies, DMV! The next total lunar eclipse won’t be until 2018.