Introduction. With second contact, the moon
completes its journey into the umbra. For as long as the next
104 minutes (but usually a shorter period) the moon will be
completely shielded from the sun’s direct rays, glowing only
with the gray to reddish–orange sunlight the earth’s dense
atmosphere refracts around the planet’s limb.
For all its beauty and the suspense it
has generated as to what color and how dark the moon would
appear during this particular totality, if we compare it to
that of a solar eclipse, second contact is almost
There are, to be sure, interesting and
important projects to pursue during totality, but the partial
phases seemed far more hectic. Now, the totality phenomena
exhibit themselves for your observation for a considerable
length of time while undergoing only the subtlest of changes
until third contact’s arrival, when the moon’s leading
edge once more breaks free of its umbral embrace.
Photograph 15-1 A near-third contact
video image of the 17 August 1989 total lunar eclipse.
The VHS video was taken with a Sony black and white camera
through a Celestron Comet Catcher. South is toward the
left-hand corner. Video taken by John Westfall.
Contact timings. As the moon’s leading
limb approaches the umbra’s edge, it is fairly easy to
anticipate second contact. Third contact is more challenging,
for the moon’s trailing limb brightens significantly during
the waning minutes of totality. Small apertures, low
magnifications and filters are best for enhancing the contrast
at the umbra–penumbra boundaries,
especially for very bright eclipses.
Attempt timing accuracies to 0.1 min (6
sec) and employ the customary procedure of tape recording
voice over WWV or CHU time signals for best results.
General color and uniformity. Carefully
characterize the tones and colors of the umbra during
totality, while remaining alert to any variations in these
characteristics with the passing of time.
To capture the colors of the moon, many
observers employ standard paint charts or color wheels
illuminated by a white light source. Artistic observers
frequently recreate the color by combining watercolors or oils
at their palettes until they get the best match. Watercolors
seem to recreate the subtle tints best. Photocopies of lunar
maps on water–resistant paper stock provide an excellent
medium for artists wishing to make frequent watercolor
renderings of the changing hues and textures as the eclipse
progresses. Once captured, these preliminaries may be
transferred to canvas to depict a single moment of totality
or, in a sequential fashion resembling a multiple–exposure
photograph, to depict the whole of totality.
Monitor various lunar features for
visibility within the umbra, especially those which are close
to the limiting resolution of your instrument. Employ a
variety of color filters to determine which ones best enhance
the visibility of specific features.
Eclipse luminosity. The darkness of the
moon’s surface at mid–totality is governed by the degree
to which the earth’s atmosphere absorbs the sunlight being
refracted around the planet’s limb and into the umbra. This,
in turn, is determined by how dusty and cloudy the earth’s
atmosphere is at the time. If there have been major volcanic
eruptions, widespread sandstorms, major forest fires or the
maximum of a major meteor shower (which may trigger increased
cloudiness and rainfall) in the months preceding an eclipse,
the moon may be almost invisible during totality, as with
eclipses in 1963 and 1964.
A five–point subjective scale for
evaluating the moon’s luminosity at mid-totality, proposed
by French astronomer André–Louis Danjon (1890–1967), has
provided amateurs with an invaluable tool for directly
comparing modern lunar eclipses and evaluating written
descriptions of historical ones (see Table 15–1).
The Danjon Luminosity (L) Scale
L = 0
Very dark eclipse. Moon almost
invisible, especially at mid–totality.
L = 1
Dark eclipse, gray or brownish in
coloration. Details distinguishable only with difficulty.
L = 2
Deep red or rust–colored eclipse.
Very dark central shadow, while outer edge of shadow is
L = 3
Brick–red eclipse. Umbral shadow
usually has a bright or yellow rim.
L = 4
Very bright copper–red or orange
eclipse. Umbral shadow has a bluish, very bright rim.
The strikingly dark eclipses of 30
December 1963 and 24 June 1964 were assigned values of L = 0.
More recently, the 30 December 1982 eclipse was rated L = 0.3
while select estimates of the 9 December 1992 eclipse ranged
from L = 0 to L = 1.2, illustrating the common practice of
using intermediate decimal values with the Danjon scale.
Bright eclipses were observed on 16 September 1978 (L = 2.5)
and 4 June 1993 (L = 3).
Make your Danjon luminosity estimates
with the unaided eye or with low–power binoculars; if you
are torn between two of the scale’s descriptive criteria, by
all means interpolate decimal values. It is recommended that
you make one estimate as close to mid–totality as possible,
and two others shortly after second contact and just before
third contact. These estimates will establish L–values for
the outer umbra. Note the times of each estimate and the
instrument used, if any.
Apparent magnitude. During totality, the
full moon’s usual magnitude of –12.7 may drop by a factor
from 10,000 to 1,000,000 times; to anywhere from magnitude
–2.7 to +3.3 or fainter.
The previous chapter dealt extensively
with apparent magnitude estimates of the partial phases; those
techniques should be carefully reviewed and applied during
totality as well. Use the method and comparison stars best
suited to the unique conditions of each totality.
Lunar transient phenomena (LTP). Chapter
14 also dealt with this important area. Monitor the lunar
features identified in Table 14–4 during totality as well as
during the partial phases. You’ll find you not only have
more time for the task, but the umbral dimming and color can
make these subtle changes more apparent.
Photograph 15-2 The totally eclipsed moon
in Scorpius, 25 May 1975. This 4-minute exposure was
taken on GAF 400 through a 55 mm lens at f/1.8. North is
to the top. Photograph taken by John Westfall.
Stellar total and grazing occultations.
During totality, the moon’s limbs are dark enough to make
the disappearances and reappearances of faint stars
encountered by the moon’s inexorable eastward drift through
the heavens readily visible.
Occultations are predicted well in
advance and widely disseminated through astronomical
publications, or are available for your viewing site through
the International Occultation Timing Association (I.O.T.A.). A
nominal fee is charged for non–members.
Timings require access to WWV or CHU
radio time signals, a tape recorder, and a telescope adequate
to the task, and timings should be made to the nearest 0.1
second with an accuracy as close to 0.2 second as possible.
You also need to obtain the precise latitude, longitude and
elevation of your observing site from a topographic map if
your observations are to have any value.
Stars will disappear along the moon’s
western limb (celestial east) and reappear at the eastern limb
(celestial west) for total occultations, and will be close to
the polar regions for grazing occultations. Grazes present
greater challenges, for you generally have to travel some
distance to get the star and the moon in proper alignment and
there may be multiple disappearances and reappearances in
rapid succession as the moon’s mountains and valleys pass
your line of sight.
On rare occasions, planets, asteroids,
comets and deep–sky objects may be occulted during totality;
these can be especially exciting and observationally important
is especially interested in receiving timings of grazing and
total occultations made during lunar eclipses.
Meteors. Meteor observations take two
forms. You might want to watch for large meteor impacts on the
moon’s surface (of course, you can do so for much longer
periods on the moon’s earthlit surface between full moons).
Or, you might prefer observing sporadic or shower meteors
which would otherwise be “washed out” by the full moon’s
light were no eclipse in progress.
Lunar meteor impacts are best watched for
by remaining alert to their possibility while conducting other
observations, most notably high–power monitoring of LTP and
other features with large–aperture instruments. Large
impacts are considered exceedingly rare and, even if one
occurs, likely to be misinterpreted as an LTP of lunar origin.
Observers with modest equipment and an
interest in meteor observing may want to stretch out in a lawn
chair during totality and monitor earthly meteor activity. An
hourly count might be made, or more extensive data on the
times (to the nearest minute), magnitudes, durations, train
characteristics and paths of observed meteors may be recorded.
These data may be especially important if the eclipse falls
near the maximum of a major meteor shower.
Others may want to use binoculars or
telescopes to watch for fainter telescopic meteors. Select a
familiar star field having stars of wide–ranging magnitudes
to simplify estimates of meteor brightness.
Meteor observations should be forwarded
to one or more of the following: the American Meteor Society,
the Meteor Section of the Association of Lunar and Planetary
Observers, the International Meteor Organization, and the
newsletter Meteor News.
Variable stars. The fainter novae,
short–period, and irregular variable stars might be observed
and their magnitudes estimated during totality if the cycle of
the full moon is likely to make them otherwise unobservable
for a week or so. Report observations to the American
Association of Variable Star Observers.
Artificial satellites. In addition to the
brighter artificial satellites, which are easily seen even
against the fully–illuminated full moon, totality presents
an opportunity to observe some of the fainter and higher ones
which may be having favorable passes at the time. Most
satellite enthusiasts have computer software which generates
predictions for their sites.
Photoelectric photometry. As with the
partial phases, photometric measurements of the umbra should
continue during totality. Singling out specific lunar features
for photometric monitoring, especially those on the LTP list,
can yield very valuable confirmation of any changes detected
by visual observers. You may also want to map the brightness
variations within the umbra. The International
Amateur–Professional Photoelectric Photometry organization
can provide guidance.
Photography. In addition to the multiple
and trail exposures recommended in Chapter 14, telescopic
photography of the moon at all available magnifications should
be attempted with still, video and CCD systems.
Photograph 15-3a, b Unusual views of a
total lunar eclipse: a total solar eclipse as seen from
the moon! Surveyor 3 images of the 24 April 1967 eclipse.
The left image was taken at 11:24 UT. a total lunar
eclipse was visilbe across East Asia, Austrialia, and the
Pacific. Photographs courtesy of the National
Aeronautics and Space Administration.
Amateurs with more than one camera may
want to use a variety of different color and black–and–white emulsions for still
photography; others will have ample time
to change film types during totality.
Particularly spectacular occultations
might also be photographed, either with a sequence of
exposures or by guiding on the moon and letting the star trail
until it disappears, or letting it trail after it reappears.
Short time–exposures, around 5 minutes,
with wide–field and standard lenses, should capture bright
meteor activity without serious film fogging.