LUNAR ECLIPSE

General Procedures

A lunar eclipse occurs when the moon passes through the shadow of the Earth. When the moon is within the umbra (or darkest) part of the Earth's shadow (see illustration), it is illuminated only by the light refracted through the Earth's atmosphere. This light is usually orange or brick-red. Totality, the length of time the moon is totally within the umbra, may last as long as 1 hour and 40 minutes. Before the moon moves into the umbra, it passes through an area of partial illumination, called the penumbra. In the penumbra, the moon appears nearly the same as when it's in the full light of the sun.

It's easy to photograph a lunar eclipse. However, because the moon is so dim during totality, you should use high-speed film. During totality, use the largest lens opening possible. This allows you to use shorter exposure times to stop the moon's motion in your photographs.

The moon may appear large to you, but when photographed through a lens of normal focal length, it will be a very small spot on the film. See "Sky Mapping".

Use the lens with the longest focal length available for your camera, and support the camera on a steady tripod. To record details on the moon, take your pictures through a telescope, spotting scope, or a binocular. See "GETTING STARTED".

By making multiple exposures of the moon at regular intervals, you can obtain an interesting sequence showing the progression of the eclipse all in one photograph. To try this technique, you can either use a camera that allows you to make multiple exposures on the same frame of film; or you can alternately cover and uncover the lens. Check your camera manual. You should use a normal-focal-length lens so that you can get the whole series in one picture. Aim your camera so that the picture will include the path of the moon as the Earth's rotation moves it across the sky from east to west.

To capture the sequence, begin taking pictures as the moon moves into the umbra. Make exposures at 6-minute intervals so that the images of the eclipse will be evenly spaced across the film frame. A normal-focal-length lens will cover an angle of view sufficient for about a 2-hour series of exposures. Since the images of the moon will be quite small, you may want to have an enlargement made.

Lunar Eclipse Exposures

Lunar eclipses vary in duration and differ greatly in apparent brightness and color. Variations in atmospheric conditions and in the distance of the moon above the horizon may affect the moon's apparent brightness, making exact recommendations impossible. Use the exposures suggested in the table "Lunar Eclipse Exposure Recommendations" as guides only. If the sky is hazy or if the moon is low in the sky, try doubling the recommended exposure time.

When you're taking single pictures of the moon, it's a good idea to bracket the estimated exposure for more assurance of properly exposed pictures. Try 1 and 2 stops more and less exposure than that recommended in the table "Lunar Eclipse Exposure Recommendations".

When the moon is partially in the umbra, where you can see a definite shadow line across its surface, select the exposure for either the umbra portion or the penumbra portion. The film cannot properly record both areas at the same time.

Gradually increase the exposure from the second contact to mid-totality; decrease the exposure from the second contact to the third contact. See "Lunar Eclipse Exposure Recommendations".

You can calculate exposure times for f-numbers other than those given in the table. Suppose your largest lens opening is f/5.6 and the table suggests f/2.8. Divide 5.6 by 2.8 and square the answer: 5.6 / 2.8 = 2, and 2² = 4. This means the f/5.6 lens opening will require an exposure 4 times as long as that required with a lens opening of f/2.8. For example, if the table suggests 1 second at f/2.8, you can use 4 seconds at f/5.6.

The moon appears to move a distance equal to approximately half its diameter in 1 minute. If the exposure time with a normal-focal-length lens is longer than 10 seconds, the moon motion is likely to be evident in the photograph. If you use a telephoto lens or a telescope with your camera, the maximum exposure time must be even shorter.

You can use the following formula to determine the approximate maximum exposure time for sharp pictures of the moon with a telephoto lens or telescope.

Lunar Eclipse Exposure Recommendations

See section "KODAK Films".

Note: All exposure tines are in seconds or fractions of a second. With color negative films, use 1/2 stop larger lens opening than indicated in the table.

Kodak, Kodak Professional, Ektachrome, Kodachrome, Plus-X, Ready-Mount, Royal Gold, T-Max, Tri-X, Wratten are trademarks.

Contents | Getting Started | Solar Eclipse | Lunar Eclipse

P-150  • April, 2002