1994 Diamond Ring Effect
The "diamong ring" effect occurs seconds before and after a total eclipse begins and ends.
Celestron 90 (f.l.=1000mm, f/11, 1/125 sec, ISO 100).
(click to read report)
How do you capture the amazing spectacle of a total eclipse with a camera? Photographing an eclipse really isn't very difficult. It doesn't even take a lot of fancy or expensive equipment. You can take a snapshot of an eclipse with a 35 mm camera loaded with fast film (ISO 400 or faster) if you can hold the camera steady or place it on a tripod.
The first step in eclipse photography is to decide what kind of pictures you want. Are you partial to scenes with people and trees in the foreground and a small but distinct eclipsed Sun overhead? Or do you prefer a close-up in which the flaring corona or vibrant prominences of the eclipsed Sun fill the frame? Your decision will determine what kind of equipment you need. Look at the photographs and captions throughout this book. They illustrate some of what can be done with a range of cameras, lenses, and telescopes, and of film and exposures.
New technologies in film, cameras, and electronics are making eclipse photography easier than ever before. Even beginners can take great eclipse photos with some careful planning. Planningis the key. The day of the eclipse is not the time to try out a new tripod or lens. You need to be completely familiar with your camera and equipment, and you need to rehearse with them weeks before the eclipse. A total eclipse grants you only a few precious minutes and everything must work perfectly. Nature does not provide instant replays.
Solor film comes in two basic types: print film (negatives) and slide film (transparencies). An advantage of print film is that it is very forgiving about exposure times. You can be off as many as three f-stops (or shutter speeds) from the best exposure and still produce an acceptable photograph. Slide film is less forgiving. If your exposure is off by more than one f-stop, your photograph is usually ruined. Slides are also less convenient to view than prints.
Slide film does have advantages, however. It requires just one processing step, which helps to retain accurate color. Slides can also be projected on a screen for large audiences.
If you were allowed only one roll of film to photograph an eclipse, it is hard to go wrong with the latest ISO 400 film from Agfa, Fuji, Kodak, and Konica. The ISO rating is a measure of the film's sensitivity: how fast it responds to light. Films with an ISO of 100 or less are "slow" and work best in bright light. Films with an ISO of 400 or more are "fast" and can work in dimmer light.
There is a trade-off between film speed (ISO rating) and resolution. As film speed increases, so does the graininess of the film. Fortunately, film technology is advancing by leaps and bounds. Today's ISO 400 films are finer grained than the best ISO 100 films were only a decade ago.
A greater threat to image sharpness, especially among beginners, is camera vibration caused by wind, flimsy tripods, and nervous photographers. ISO 400 films allow you to use faster shutter speeds, which can help minimize these bad vibrations.
In general, films that work well for everyday photography also work well for shooting eclipses.
Phases of the Annular Solar Eclipse of 1994 May 30
Celestron 90 (f.l.=1000mm, f/11, 1/125 sec, ISO 100).
(click to see more photos)
When viewing or photographing the partial phases of any solar eclipse, you must always use a solar filter. A solar filter is also needed for observing all phases of an annular eclipse, when the disk of the Moon does not block the entire face of the Sun. Even if 99% of the Sun is covered, the remaining crescent or ring is dangerously bright. It is like looking at a welder's torch; it will painlessly burn your eyes. Failure to use a solar filter can result in serious eye damage or permanent blindness. Do not look directly at the Sun without proper eye protection!
During totality, however, when the disk (photosphere) of the Sun is fully covered by the Moon, it is completely safe to look at this phase of the eclipse without any solar filter. In fact, you must remove the solar filter during totality or you will not be able to see or photograph the exquisite solar prominences and corona.
Solar filters for telescopes and cameras are usually made of metal-coated glass to provide the highest resolution, although aluminized Mylar can also be used. These filters vary in the wavelength (color) of light they transmit. Aluminized Mylar filters show a blue-gray Sun, while the more expensive metal-coated glass filters transmit a more realistic orange Sun. Materials and techniques that should not be used for solar filters include exposed color film, stacked neutral density filters, smoked glass, and crossed polaroid filters.
There are three types of solar filters: eyepiece, off-axis, and full-aperture. Eyepiece filters, furnished with some small telescopes, are not safe and should never be used for viewing the Sun. The tremendous heat generated at the eyepiece can easily shatter or crack the filter, allowing the full intensity of the Sun's light to be magnified and focused on your retina. Throw eyepiece filters away.
The only safe solar filters for telescopes and cameras are full-aperture and off-axis filters, both of which fit over the objective (front end) of the telescope or camera lens. A full-aperture solar filter is a cap with a solar filter mounted across its entire top. An off-axis solar filter is a cap with a hole off to one side into which the solar filter is mounted. Off-axis filters are cheaper than full-aperture filters.
If you use an off-axis solar filter with any catadioptric telephoto lens, the focus of the Sun will change significantly when you remove the filter to photograph totality. You must refocus. The optical field of a catadioptric system is not flat, and focusing with only the edge of the mirror is quite different from focusing with the whole mirror. In a full-aperture solar filter, the filter occupies the entire top of the cap and thus the focus is averaged over the entire surface of the mirror. No refocusing is needed when the filter is removed at the beginning of totality or when the filter is replaced at the end of totality. Full-aperture solar filters are preferred.
If your telescope has a finder scope, be sure to place a small Mylar solar filter over its objective lens to protect your eyes and to keep the finder cross-hairs from burning. If you don't have any Mylar, keep the lens cover on the finder scope.
Most telescope manufacturers and dealers offer glass solar filters for their products. Both types of solar filters are advertised in the major popular astronomy magazines (Astronomy, Astronomy Now, and Sky & Telescope). Solar filter retailers are also listed in Totality - Appendix C .
For more information, see:
Totality - Eclipses of the SunSecond Edition
by Mark Littmann, Ken Willcox and Fred Espenak
Order Totality from MrEclipse.com
All rights reserved. This material may not be reproduced, published, copied or transmitted in any form, including electronically on the Internet or World Wide Web, without written permission of the authors.
Contact Espenak (at MrEclipse) for more information.
All photographs, text and web pages are © Copyright 2007 by Fred Espenak, unless otherwise noted. All rights reserved. They may not be reproduced, published, copied or transmitted in any form, including electronically on the Internet or WWW, without written permission of the author. The photos have been digitally watermarked.
The photographs may be licensed for commercial, editorial, and educational use. Contact Espenak (at MrEclipse) for photo use in print, web, video, CD and all other media.
Last revised: 2008 Jan 22