Solar Eclipse Observing--Environmental Studies
Introduction. In the
fifteen–or–so minutes on either side of totality or
annularity, subtle changes take place in the environment and in
the behaviors of wildlife. Family members without extensive
astronomical equipment or projects to conduct can make valuable
contributions as observers of their physical and biological
Pinhole camera images. As the sun
dwindles to a thin crescent and the ground lighting dims,
hundreds of tiny images of the crescent sun appear projected
among the shadows cast by leaves beneath their trees. Nature
produces this fascinating phenomenon in much the same fashion as
observers who make pinhole camera viewing devices; in this case,
the pinholes are the tiny spaces between the densely packed
A worthwhile experiment for even young
children would be to try out a variety of manufactured and
home–made devices to determine what apertures produce the
clearest and sharpest pinhole images. Some recommended household
items are colanders, sifters, strainers, squares of pegboard and
perforated convection–oven trays. Even the fingers of their
own hands, spread slightly apart, will project these crescent
shapes. They might also be alert to the types of trees and
leaves, or other foliage, which produce the best natural images.
Diminishing light. As the sun
dwindles to a smaller and smaller crescent, the surrounding
landscape very gradually takes on a late–afternoon appearance.
In the final minutes before totality, however, the changes in
lighting become quite striking, and the skylight seems to
diminish in stepped increments rather than with a smooth,
gradual transition toward darkness.
The changing colors of the surrounding
landscape and distant clouds can be quite striking as well, with
yellows and oranges most often described. Nor do light intensity
and color changes necessarily mirror themselves coming out of
totality. Many describe the sun’s return as abrupt and the
colors less pronounced or of different hues following totality,
while others believe these perceptions to be more psychological
in origin; certainly, further investigation is warranted.
Artists and poets have a distinct advantage
over photographers and technocrats in capturing
diminishing–light phenomena and the feelings that accompany
Wildlife behaviors. Animals are very
perceptive to changes in their environment. Their responses to
the unexpected early nightfall and even more unexpected daybreak
after such a short night, can make a fascinating study.
Livestock, wild birds, squirrels, insects
and even domesticated pets will behave in unusual and
interesting ways because of the environmental changes that
accompany a total or dark annular solar eclipse. Some animals,
accustomed to feeding schedules dictated by dawn and dusk,
exhibit changes in eating habits on eclipse day and, according
to some reports, for several days after an eclipse. Others,
roosters, for example, crow on cue as twilight comes and goes,
and appear to experience no disorientation at all.
Mosquitoes have been known to go on feeding
frenzies, and even aquatic life is not spared; fish are
reportedly more willing to bite around totality (if one can
imagine taking time out from such a celestial spectacle to go
fishing), and their neighboring amphibians have been heard to
carry on quite loudly.
Studies of solar eclipse effects on
individual forms of wildlife, except for occasional anecdotal
accounts of diminished milk production by cows and egg
production by chickens, are few at best. People with interests
in these areas are encouraged to pursue them.
Meteorological observations. Most
eclipse–chasers have at least a basic familiarity with
meteorology and weather forecasting. Many amateur astronomers
carry along meteorological instruments to measure temperature,
wind, air pressure and humidity changes throughout an eclipse.
For others, a primary reason for observing the eclipse may be
There are significant changes in the
weather during eclipses. As the amount of sunlight is reduced,
the temperature of the surrounding air begins to fall. This
results in corresponding changes in the barometric pressure,
wind speed and direction, dew point and humidity. These changes
can sometimes result in unexpected fog or dew formation that can
hinder eclipse observations and photography; they should be
anticipated and equipment should especially be monitored for dew
formation if the relative humidity is high.
A simple grade–school experiment can
quickly determine the dew point at an observing site prior to
totality. Slowly add a few shards of ice, a little at a time, to
a glass or metal container of water. The moment a thin mist of
dew forms on the outside of the container, insert a thermometer
into the water. The water temperature at that moment is the dew
point of the surrounding air, or the temperature at which dew
and fog will form. If the air temperature is sufficiently
higher, you should have no problem with dew; if it is within
five degrees or so, it would be wise to monitor your equipment
Recording readings from meteorological
instruments are good projects for younger family members or
those without astronomical observations to conduct, and are
excellent additions to your eclipse journal. Instruments to
consider taking are thermometers, barometers, hygrometers,
anemometers (simple hand–held wind–speed devices are
available from most science supply houses), and compasses for
determining wind direction.
If your site is near an airport or
television station, consider making prior arrangements with the
resident meteorologists to allow you to stop by after the
eclipse and photograph their chart recorders or copy their data
for the various weather elements. Some will also have
instruments which record sunlight intensity throughout eclipse
day. An interested researcher or astronomy group might wish to
query weather stations all along the eclipse path to obtain
Weather satellite imagery. Many
schools and amateur meteorologists have access to inexpensive
groundstation equipment capable of receiving real–time U.S.
NOAA and Russian Meteor satellite images on their personal
computers. Local HAM radio clubs or weather stations may be able
to put you in contact with them.
Photograph 6-1 GOES weather satellite
image of the 11 July 1991 total solar eclipse. Note
the moon's shadow west of Baja California, Mexico.
Photograph 6-2 GOES weather satellite
image of the 10 May 1994 annular eclipse. Note the
moon's shadow over the Midwestern states. Also note
the lack of sharpness when compared to the moon's shadow in
If a satellite pass coincides with the time
of totality, the moon’s shadow on the earth’s surface (or on
cloud tops) should be visible in the image received. Stored in
their computers as TIFF (Tag Image File Format) files, they may
be easily copied
onto 3.5–inch high–density microdisks and transferred to
your own hard drives for viewing later. Service bureaus, desktop
publishing companies and photo processors in major metropolitan
areas can provide photographic prints from these computer files.
The original NOAA images, incidentally,
contain both visible and infrared frames side–by–side; the
latter may be processed, through the system’s software, to
provide remote temperature readings within the moon’s shadow.
Following the eclipse, weather satellite
imagery of the moon’s shadow might also be found on computer
bulletin board systems (BBS’s) as GIF (Graphics Interchange
Format, pronounced JIF) files that may be downloaded by modem to
your own hard drive or high–density microdisk and viewed with
the appropriate software.
Most computer desktop publishing and
painting software supports TIFF files (identified by the suffix
.TIF). GIF files (.GIF) save and retrieve slower than TIFF
files, but use an efficient compression algorithm which keeps
file size small and saves disk space, making them a favorite for
BBS’s and for more rapid uploading and downloading.
Photographic projects. A
light–colored surface, such as the side of a house, a street,
sandy ground, bed sheet, or piece of white cardboard, will make
the leaf–formed pinhole camera images of crescent suns stand
out for photography. Still or video available–light
photographic sequences, at fixed aperture and shutter speed,
would be useful in determining when these images are first and
last visible on each side of totality or annularity.
Photography of diminishing light effects
may be attempted, especially with low–light video cameras.
Also, don’t neglect photographic studies of wildlife behaviors
and photo documentation of chart recordings from weather