Total Lunar Eclipse 28 September 2015

On the early morning of 28th September 2015 there will be a total eclipse of the Moon. Details of the eclipse can be found here: http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2015Sep28T.pdf And here: http://www.skyandtelescope.com/astronomy-news/observing-news/get-ready-for-septembers-total-lunar-eclipse-091420155/ 

Times are in UTC, so add an hour for British Summer Time.

The total phase is between 0311 BST and 0423 BST. The penumbral phase begins at 0111 BST and ends at 0622 BST.

The examples in this post were taken during the March 2007 Total Lunar Eclipse unless stated otherwise using a Canon 300D DSLR and 800mm lens.

Lunar Eclipse March 2007 - Partial Phase

Partial phase: Location Hampshire, UK Taken at ISO200, 1/125s with 800mm lens at f/11 on Canon 300D Taken at 2200 UT

Lunar Eclipse March 2007: Just before totality

Just before totality: 4 seconds at ISO400 f/11, 800mm on Canon 300D Location Hampshire, UK

Lunar eclipses are perfectly safe to view throughout the eclipse and pose no risk to eyesight or equipment (unlike a solar eclipse). They are the result of the moon, earth and sun being aligned such that the moon passes through the earth’s shadow as cast by the sun. What happens is that there is a faintening of the bright full moon as the moon passes through the “penumbra”. This may not be discernible to the naked eye but maybe by camera.

During mid eclipse, as the moon passes through the “umbra” of the shadow, then the moon darkens considerably and observers will see a gradual darkening until the moon is fully in shadow. Photographs at this stage show a reddish arc crossing the moon until the moon is fully reddish in colour.

Lunar Eclipse March 2007: Mid Eclipse

Mid Eclipse: Location Hampshire, UK f/11, 800mm on Canon 300D 20 second exposure at ISO400, Guided

During the relatively long total phase the moon is very dark and reddish in colour, though how dark and how red depends on many factors.

Photographing the eclipse has challenges. A DSLR is the best type of camera to use as it can be directly attached to a telescope or use a telephoto lens. Normally a full moon would need an exposure of about 1/200s at ISO 200 and f/10. You should check your exposures with your camera and lenses (or telescope) against a normal full moon. Lenses with less than about 200mm focal length will not have enough magnification to show much. However, one could experiment with short focal lengths to create a montage of the moon throughout the varying phases of the eclipse.

With a long focal length you can show considerable detail. I have a 100-400mm focal length zoom lens with a 2x extender giving an 800mm focal length system which the above photographs were  taken with (on a Canon 300D) during the March 2007 lunar eclipse.

However, the resulting f/11 configuration requires four times longer exposures than the 400mm f5.6 lens (or a 4x ISO – though that introduces more noise). The moon is considerably darker so exposures of several seconds become necessary which is only possible if the camera can be guided, otherwise movement due to the earth’s rotation blurs the image. Putting the camera onto a “piggy back” mount on a guided telescope or a special guided camera mount (such as sold for about £300 by the likes of iOptron, Skywatcher and Baader).Otherwise you’ll need your camera to be tripod mounted and to increase the ISO to keep exposures below about half a second beyond which the image will blur.

It will be necessary to manually focus the camera and put settings onto manual as the camera will not focus or expose correctly if left on automatic settings. Try focusing on a bright star first using (if your camera has it) via the LCD panel (or “LiveView” on a Canon).

Fortunately during the 70 minutes or so of totality you have plenty of time to experiment with differing camera settings to get the best results. Try shorter exposures at higher ISOs or longer exposures at lower ISO to assess the quality. Various online resources and books (eg Covington’s Astrophotography for the Amateur) provide guidance on exposures etc.

Here are some other examples from the 2008 eclipse (when there was a lot of cloud about):
Lunar Eclipse February 2008

Good Luck and let’s hope for clear skies.

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