Comet Promises Big Show
Herman M. Heyn
astronomical objects and events is not solely the province of professional astronomers
wielding giant telescopes. Many of the beautiful photos in astronomy textbooks
were taken by amateur astronomers using everyday camera equipment. With Comet
Hale-Bopp fast approaching, now is a perfect time to learn the not-too-difficult
science and art of still-camera astrophotography. Nine pieces of equipment are
- A 35 mm single
lens reflex (SLR) camera is ideal. Its shutter speed control must have a 'B'
or 'T' setting for time exposure; the camera must operate mechanically (not
by battery) at that setting. The Pentax K-1000 is one such camera.
- The best all-around
still camera lens has a 50 mm focal length and a speed of f/2 or faster.
- A reasonably
steady tripod is required. Be sure it can tilt the camera toward the zenith
- Depressing the
shutter button with your finger introduces ruinous vibrations during time
exposures. Use a cable release attachment, the type with a locking collar
that locks with one hand.
- To ensure against
jitters as the camera shutter opens and closes, use a piece of black posterboard
as the final shutter.
- You can count
off seconds, but more practical is a timing device. A battery-powered metronome
ticking once per second is very handy in the dark.
- A dim, red LED
flashlight, or a white one with red tissue paper taped over it, will preserve
your night vision while reading star maps, camera settings, or notes.
- Always keep
records of your astrophoto efforts. Data should include date, location, sky
conditions, camera and lens specs, film type, and the time, subject, and length
of each exposure. A 14-inch clipboard can hold your record sheet.
- Last is the
35 mm film. Start with ISO 400 slide film. Slides show exactly what you photographed.
Once you know what to expect, you can try print film, as well as faster films.
Among the latter are Kodak Gold 1000 and Ektachrome P1600 and Fujicolor Super
G Plus 800.
Now that you have
the required equipment (see photo), you are ready to take astrophotographs.
Pick a site as far as possible from urban light pollution and a night without
a bright Moon. Then follow these five steps:
- Load the film
and snap a daylight scene for reference purposes. Remove any filters, as they
can cause internal reflections in night photography.
- At the site,
mount the camera on the tripod, attach the cable release, set the shutter
speed to 'B' or 'T', focus on infinity, and open the lens to its fastest (widest)
setting. Organize your timer, clipboard, and red flashlight.
- Aim your camera
at a constellation and frame it as nicely as you can. Recheck the focus and
aperture, and cock the shutter. Start your metronome at one tick per second.
- Holding the
black posterboard in front of the camera, depress the cable release button
to open the shutter, and lock the cable.
- On the count
of "one thousand zero," move the posterboard away from the camera to begin
the exposure. Continue counting: "One thousand one, one thousand two..." At
about "one thousand 17" (17 seconds), return the posterboard to the front
of the camera and unlock the cable release to close the shutter. Wind the
film. Congratulations, you have just taken your first astrophoto!
If your school
has a planetarium, you can practice astrophotography in it. Just remember that
because the dome is not at infinity, the camera must be refocused for each shot.
In the table below
is a list of photogenic evening constellations and recommended exposure times
(in seconds) for a 50 mm lens. Note that the farther above or below the celestial
equator you point, the longer you can expose before stars leave visible trails.
To determine the maximum exposure time without trailing, use the formula: 850/focal
length x cosine declination.
is desired. The two best constellations for such photos are Orion and Ursa Major.
With ISO 400 film and the lens closed to f/4 to avoid overexposing the sky,
try a 10-minute exposure. The ultimate, classic star-trails photo is one of
an hour or longer centered on Polaris. Close the lens to f/5.6.
Meteors are another
possibility. There are about eight "shooting stars" per hour every night, but
your chances improve considerably during major meteor showers, such as the Perseids
and Geminids. The Perseids peak the evening of Aug. 11 and the Geminids the
evening of Dec. 13. Use fast film with the lens wide open. Aim anywhere in the
sky and take consecutive 5-minute exposures.
And then there
is Hale-Bopp, which, if it lives up to its billing, will be the best comet in
decades. From mid-January to mid-March, the comet will be in the predawn sky,
and from then until early May, it will be in the post-sunset sky. Use ISO 800
and faster film. With the lens wide open, shoot from 15 to 35 seconds in 5-second
increments. For perspective, put trees, buildings, and even people in your foreground.
One last astrophotography
suggestion: the near-total lunar eclipse of March 24. With a 50 mm lens, the
Moon's image is quite small; a 135 mm or longer focal length is better. Use
ISO 200 film and bracket your exposures -- that is, try several camera settings
for each stage of the eclipse. While the Moon is full, use 1/400 seconds at
f/16, f/11, and f/8. As the shadowed area grows, use progressively wider stops,
such as f/11, f/8, and f/5.6. As the umbra enlarges, use f/11, f/8, and f/5.6.
At mid-eclipse, when only a sliver of the Moon remains, open to f/4 and bracket
from 1/15 to 2 seconds.
is within your reach. Give it a try!
|| Leo (18)
HERMAN M. HEYN
is a long-time amateur astronomy and astrophotographer living in Baltimore.
He is on the staff of the Maryland Space Grant Consortium. Many of his astrophotos
have appeared in Sky & Telescope magazine and in astronomy books. Heyn can often
be found loitering on street corners in downtown Baltimore at night -- along
with his Meade 8-inch Schmidt-Cassegrain telescope, which he encourages passers-by
to look through. He welcomes readers' reports on their astrophoto efforts. His
mailing address is 721 E. 36th St., Baltimore, Md. 21218; phone: (410) 889-0460.
- Aguirre, E.
"Comet Hale-Bopp is Coming." Sky & Telescope, Nov. 1995, p. 20.
- Eicher, D. "See
the Great Evening Comet." Astronomy, Oct. 1996, p. 81; "Here Comes Hale-Bopp."
Astronomy, Feb. 1995, p. 68.
- Hale, A. Everybody's
Comet: A Layman's Guide to Comet Hale-Bopp. 1996. High-Lonesome Books, P.O.
Box 878, Silver City, N.M. 88062. A general introduction by one of the astronomers
who discovered the comet.
- Machholz, D.
An Observer's Guide to Comet Hale-Bopp. 1996. MakeWood Products, P.O. Box
1716, Colfax, Calif. 95713. A self-published observing manual by an active
comet hunter; full of useful charts and hints.
- Schaaf, F. Comet
of the Century: From Halley to Hale-Bopp. 1996. Springer Verlag. An overview
by a prolific amateur and observer.
Books About Comets
- Brandt, J. and
Chapman, R. Rendezvous in Space. 1992. W.H. Freeman. Excellent and up-to-date
introduction by two leading comet experts.
- Levy, D. The
Quest for Comets. 1994. Plenum Press. Personal story of comet discovery and
comet science by an amateur astronomer who has found many comets.
- Sagan, C. and
Druyan, A. Comet. 1986. Random House. Beautifully produced and eloquently
written; very good on historical material and human connections.
- Yeomans, D.
Comets: A Chronological History. 1991. Wiley. Rich source of historical material
Comets in General
D. "Where Do Comets Come From?" Astronomy, Sep. 1990, p. 28.
- Ferrin, I. &
Guzman, E. "How a Cometary Nucleus Turns On." Sky & Telescope, Aug. 1981,
- Morrison, D.
"Target: Earth." Astronomy, Oct. 1995, p. 34. On collisions of comets and
asteroids with our planet.
- Pendleton, Y.
and Cruikshank, D. "Life from the Stars?" Sky & Telescope, Mar. 1994, p. 36.
On how comets may have brought the ingredients for life to the early Earth.
- The March 1987
issue of Sky & Telescope was devoted to explaining what we learned from Comet
Halley; it is an excellent resource.
- Bortle, J. "A
Halley Chronicle." Astronomy, Oct. 1985, p. 98. A chronology of each pass.
- Shibley, J.
and Naeye, R. "Hyakutake's Spring Surprise." Astronomy, July 1996, p. 74.
- Talcott, R.
"Comet Encke Returns." Astronomy, Jan. 1994, p. 87.
- Weaver, K. "What
You Didn't See in Comet Kohoutek." National Geographic. Aug. 1974.
- Weissman, P.
"Making Sense of Shoemaker-Levy 9." Astronomy, May 1995, p. 48. Excellent
summary of this comet's collision with Jupiter.
- DiCicco, D.
and Robinson, L. "Comet Photography for Everyone." Sky & Telescope, May 1996,
- Dilsizian, R.
"Catch a Comet on Film." Astronomy, Jan. 1996, p. 78.
- Edberg, S. and
Levy, D. Observing Comets, Asteroids, Meteors, and the Zodiacal Light. 1994.
Cambridge University Press. A handbook for amateur astronomers.
- Levy, D. "How
To Discover a Comet." Astronomy, Dec. 1987, p. 74.
Hale-Bopp on the
World Wide Web
ANDREW FRAKNOI is the chair of the astronomy department at
Foothill College in Los Alto Hills, Calif. He is the director of the ASP's Project
ASTRO and lead author of a new astronomy textbook, Voyages Through the Universe,
published by Saunders. He tells us that his son Alex, now 3, knew the words
"planet," "star," and "Moon" by age 2.
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