Posts Tagged ‘lunar eclipse’

This composite image shows four phases of the total lunar eclipse of June 15, 2011. The moon was eclipsed in the rising phase. In addition, we faced clouds in large part of the sky. Nevertheless, we captured enough beautiful frames.

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It can be a lot of fun to capture some photos from astronomical event. In this post, I explain how to do so for a lunar eclipse since a great total lunar eclipse is coming.

Assumptions: you have a tripod, a (digital) SLR camera, and perhaps a cable release. That means you do NOT need any dedicated astronomical telescope for this purpose.

If you are going to shoot some photos from the eclipse, there are some simple tricks you can keep in mind. First of all, use a tripod and cable release to avoid shaking. Second, try a few different exposures to make sure you neither over expose nor under expose the photos. These two points also apply to solar eclipse photography. The exact setup of the f/ratio and exposure depends on the darkness of the eclipse.  Since this eclipse will be probably a dark one, I guess I try the followings:

F/ratio : a fast optics like f/5.6 or f/4.0 is always good in astrophotography. If maximum opening of your objective is like e.g., 5.6, close it one more step to have a better optical quality.

Exposure : with current digital cameras, you can check the histogram (intensity distribution) of the captured frame immediately. The distribution should have a mean value about the half of the depth of your chip pixels. For instance if your camera has a 12 bit chip (like mine), you have a full well depth of 2 to power 12, which is 4096. In this example, a histogram which peaks about 2000 is good. Also note that you should avoid overexposing: i.e., the histogram tail toward larger values should NOT touch the very end. In brief, use both visual inspection of the photo and histogram to make sure you have the right exposure time.

All in all, try exposures like 1/15 to 1/125 sec for the partial eclipse. Take one or two more exposures with one step more or less to make sure you captured everything.  To record the Moon during totality, you need a few seconds of exposure depending on the darkness of the eclipse. Unlike a solar eclipse, you have plenty of time. So check the captured frames to be 100% on the safe side.

ISO : I usually use 800 or 400. It actually depends if the selected sensitivity in your camera is too noisy or not. If you are doubtful, take ISO 400 as initial guess. The higher the sensitivity, the lower the difference between the maximum and minimum in your Photo. Therefore, a medium ISO value keeps both the dynamic range and the chip sensitivity.

Focal length : as long as you can. If you have a tele lens of F=100 to 300 mm, try that. Be careful about the f/ratio of tele lenses. You might have a very long focal length lens like F=500mm or more but with a f/ratio like f/8 or even worse. In this case, you have to increase the exposure time.

Focus : that is the master key for astrophotography.  Never underestimate the importance of a great focus. Invest enough time in advance to focus your system.

Camera settings : if you have a digital SLR camera, you can check  this link to adjust general settings of your camera. For instance, you should use the maximum resolution of the camera.

Telescopic observations : if you have a telescope and a digital SLR camera or a CCD, you can of course take advantage of them and record great photos. The long focal length of a telescope will allow you to capture details that cannot be recorded with normal photography. Get the proper T-mount and adapters to connect your camera (body) to the telescope (the prime focus method).  This way, the image that forms in the focal plane of the optical system will be on the chip of the camera.  The telescope then acts as a camera lens. That is an easy way for telescopic astrophotography. You can use other methods of attaching a digital camera or CCD to a telescope for larger magnifications as well. I try to explain details of this method in a separate post.

I wish you a nice weather condition, a great seeing, and perfect photos !

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A great total lunar eclipse is coming !

While total eclipses of the sun are rare at any location on the Earth, eclipses of the Moon can be observed without the need to travel. A lunar eclipse is visible from the whole hemisphere of the Earth for which the Moon is above the horizon.

As seen in the Moon path below, it almost goes through the center of the Earth’s umbra. That means the Moon will be specially dark during the totality period. The brightness of lunar eclipses is often described in terms of the Danjon scale:

0: very dark eclipse. Moon defficult to see, appears steely dark.

1: dark. features like maria or craters are difficult to distinguish.

2: dark red eclipse.

3: eclipsed Moon quite bright, reddish. Maria easily visible.

4: very bright eclipse, with Moon appearing coppery red-orange.

The last total lunar eclipse I have observed falls in the category 3 or 4. I can remember its cooper red color. I hope the upcoming eclipse will be way darker.

In the eclipse of June 15, 2011, the Moon starts moving into the Earth’s penumbra at 17:25 UT while it enters the umbra at 18:23 UT.

The Moon will be in the shadow completely between 19:22 and 21:03 UT. At that time, it starts leaving the Earth’s umbra.

This eclipse will be observable from Africa, south/west Asia, as well as east Asia, and Europe. For western European observers, the eclipse starts while the Moon is rising. While observers from south America can watch part of the event, north America observers have no chance.

For more detailed information, you can check this file (the file is downloadable from Nasa/Eclipse webpage as well).

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