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Wednesday, December 07, 2011


Total Lunar Eclipse - December 10-11, 2011

Northern horizon as seen from Adelaide at 23:45 pm AECST on December 10 visualized in Stellarium. The Moon has begun to enter the darkest part of Earths shadow (click to embiggen). Similar views will be had elsewhere in Australia at the equivalent normal time.

On the evening of the Saturday 10th December and the morning of Sunday the 11th there is a total lunar eclipse visible from all of Australia (as well as South-East Asia, Indonesia, parts of Africa, Europe and North America).

The eclipse starts with the Moon high above the northern horizon. You have to stay up late and contine into the cold of the early morning to see it, so dress warmly and have plenty of hot cocoa on hand. This eclipse is not as long as the June 16 eclipse but it occurs much earlier and is still quite dark, so is well worth staying up for, although it is too late for the younger children.

The eclipsed moon below the Hyades, looking north at 1 am local daylight saving time as seen from Adelaide, SA. Click to embiggen.

The Moon enters the darkest part of the Earth’s shadow (the Umbra) at 23:46 pm (daylight saving time) on the east coast, 23:16 ACDST for the central states and 20:46 pm in Western Australia.

Over the next hour you will see the shadow slowly creep over the Moons face until the Moon is covered by the shadow of the Earth The deepest part of the eclipse is 1: 32 am daylight saving time on the 11th eastern states, 1:02 am daylight saving time central states and 22:32 pm WA). You should see the stars becoming more visible as the Moon darkens.

What is the best way to watch the eclipse? Well, with the unaided eye to start with. The sight of the shadow crawling over the Moon will be awesome, and you can watch the sky darken and the stars pop out as the eclipse progresses. The Moon will not be completely dark, but will be a deep red colour. Unlike solar eclipses, lunar eclipses are perfectly safe to look at.

The area around the Moon will be beautiful, with the Hyades and Pleiades clusters and the constellation Orion dominating the sky. In the east mars is risng above the horizon, and in the west Jupiter is seting. You may even see a satellite going over or a meteor or two.

You can also use binoculars; the eclipse will look quite nice in binoculars, and you will be able to see the darkened part of the Moon clearly. In a telescope, you will notice that the Earth's shadow is not sharp. You can use a low power lens to see the entire Moon to best effect, or with a high power scope you can time when various craters are covered by the shadow.

Photographing the eclipse can be done with simple digital cameras. You can just point the camera through your telescope lens and press the button, that works! For binoculars though, other than at maximum eclipse the Moon is too bright and the bright part will be over exposed.

Partial Lunar eclipse as seen from Adelaide at 21:30 pm, 26 June 2010. 4" Newtonian Reflector, 20 mm Plossl eyepiece and Canon IXUS 100 IS (400 ASA, 1/15 exposure). Click to embiggen.

For photography without a telescope, you will need a tripod or something to keep the camera steady as you take the photo. You will need to take the photo on the fastest setting you can to avoid overexposure.

Most simple digital cameras have a night mode, or allow you to set the exposure for a few seconds or more , but for most of the eclipse the Moon will be so bright you should use something like a daylight setting with no flash - experiment a little the night before to find the right settings).

If your camera has a zoom setting, zoom out to the maximum optical zoom.

You can get more information (eg twilight times) from the eclipse section at Southern Skywatch.

Cloud cover predictions can be found at SkippySky.

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Lessons from observing the lunar eclipse

Here are four lessons I learned from getting up early this morning to view the lunar eclipse:

Sloppy is okay
Sleep is bad
Don't breathe
Back up

I got up at 4:30am MST to set up my telescope. I had it outside covered all night, but now I had to get it aligned and ready. I didn't bother trying to center either of the two alignment stars, choosing to accept wherever the telescope pointed. That worked out fine. The telescope tracked the moon perfectly, at least for visual observing.

I knew I wasn't going to see any of the total eclipse. "Red Mountain Observatory" is a significant exaggeration of the term "observatory." It's just my telescope on wheels that I roll out to view. But Red Mountain is no figment of my imagination. It looms large in the west. As a result, I knew I would not see any of the totality. And I knew it was going to be cold, okay - cool (26 degrees f and 47% humidity). So I was considering sleeping through it.

That would have been a mistake. I got to experience almost an hour of the eclipse, starting at about 5:49am when the earth's shadow first hit the moon. Red Mountain didn't interfere at all until 6:37am. Those 48 minutes at the telescope were well worth a little lost sleep. And, in a way, the best was yet to come. Between 6:37am and 6:40, when the moon slipped completely below the mountain, the view was stunning. I had not expected to enjoy seeing the mountain interfere with the eclipse, but it was amazing seeing the moon being rapidly swallowed by the rocky cliffs.

I was worried about dew, but thought it would not be much if any of a problem. Even so, I attached my dew shield and I wished I had ordered a heater months ago (I ordered a DewBuster from Ron Keating a few days ago, but it won't be here for a few weeks). The end result was there was nothing to worry about. The telescope didn't attract moisture. But my eyepiece did. I was spending a lot of time looking through it and either my body heat or breathe was fogging up the eyepiece and then freezing. It was easy to wipe off but it kept happening until I started holding my breathe whenever I was looking through the eyepiece. That worked.

I have not spent much time looking at the moon, and almost no time looking at the full moon. I knew my 40mm eyepiece had a wide enough field of view to take in the whole moon. But it didn't have much more room than that. It would have been nice to frame the moon with a little more sky around it. If I could just back up five feet. Oh wait, that only works when taking family photos. So I need to look into either an eyepiece with a wider true field of view or a focal reducer.

Red Mountain Observatory
Lunar eclipse video clip http://alexeysen.livejournal.com/553.html
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