A total lunar eclipse is a spectacular event, and one that happens infrequently enough that it's well worth going outside to gaze at. While you're at it, bring along your camera and a sturdy tripod to mount it on. Although it can be challenging to get good eclipse photos because of the vast reduction of the Moon's light during totality, with a little preparation it can be done.
A lunar eclipse occurs when the Earth lies between the Sun and Moon, and the Moon passes into Earth's shadow. In a total lunar eclipse, the entire Moon is immersed in Earth's umbra, the dark, inner part of the shadow. Unlike a solar eclipse, which is far too bright to look at (except through special filters) without risking blindness, it's perfectly safe to look at all stages of a lunar eclipse.
The Challenge of Lunar Eclipse Photography
Photographing the early partial stages of a total lunar eclipse is much likephotographing a non-eclipsed Moon. As a lunar eclipse occurs at Full Moon, photographing the onset of the partial phases is like shooting any Full Moon. Soon, though, you will have to compensate for the decrease in light as more and more of the Moon slips into Earth's shadow. This is done by changing the ISO, f/ratio, and/or exposure time, while ensuring that the camera remains in focus. At the onset of totality, the reduction in light is particularly dramatic.
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Stages of a Total Lunar Eclipse
The lunar eclipse begins when the Moon passes into the penumbra, the faint outer part of Earth's shadow. If you were an observer on the Moon, from within the penumbra, you would see the Earth as partially covering the Sun. As viewed from the Earth, however, the penumbral phase of the eclipse is barely noticeable, if at all.
It's only when the partial eclipse begins, and the Moon starts its slide into the umbra, the dark, central part of Earth's shadow, that the action really starts. It will seem as if a dark bite is taken out of the edge of the Moon. (If you were on the Moon, within the "bite zone," the Sun would be totally eclipsed by the Earth.) The bite grows larger, and within a half hour or so, half the Moon is in shadow. The light quickly dims, and soon the bright, sunlit part of the Moon will be but a thin crescent, with the rest of the Moon now faintly visible as a pale, ruddy glow. Then the crescent will shrink to nothing as the entire Moon slips into the Earth's umbra, and the eclipse is total.
The total phase of a lunar eclipse can last up to 1 hour 45 minutes. Although no direct sunlight touches the Moon during totality, you can still see the Moon bathed in a faint reddish glow because Earth's atmosphere refracts sunlight, and bends the light of Earth's sunrises and sunsets around the limb of our world. Total lunar eclipses can vary greatly in brightness, with some appearing bright and coppery or orange, and others so dark that they're barely visible. (Eclipses tend to be dark after major volcanic eruptions pump a lot of ash and dust into the air. During an eclipse, the Moon may not appear uniformly bright; often one limb will be notably lighter (or darker) than the rest of the Moon, and this may shift as the eclipse progresses.
As totality ends, one of the Moon's limbs (the opposite from before) will appear as a bright thin crescent, and the phases described earlier will repeat, except in reverse, until the Moon is back to normal.
Camera
Ideally, you should have a digital SLR or a mirrorless interchangeable lens camera, and a lens with a relatively long focal length. (I've done most of my eclipse photography at 200 or 300mm.) You should be able to manually adjust settings such as white balance, ISO, exposure length, and f/ratio, as well as manually focus the camera. It's helpful to have a LiveView mode to aid in focusing.
That said, you can still get decent photos using a compact point-and-shoot camera, provided it has some capacity for manual settings, particularly exposure length. Few basic point-and-shoots allow you to focus manually, but many have a setting for shooting landscapes at a distance (indicated by a mountain icon), which you will want to use. Point-and-shoots are best for astronomical landscapes, wide-field shots in which the eclipse is framed by foreground objects. For example, I shot the photo below on March 3, 2007 with a Canon PowerShot SD630 point-and-shoot. Point-and-shoots are also good for capturing the scene just before totality, when the Moon appears as a thin, bright sunlit crescent and the rest of its disk is lit with a pale reddish hue.
發表於 2015-9-27 22:05
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