Total Lunar Eclipse October 27/28
There will be a total eclipse of the Moon beginning on the evening of
Wednesday October 27 visible all across Canada. The Moon will
pass through
the upper part of the Earth's shadow, being totally eclipsed for 1 hour
and 21 minutes. Details of the eclipse can be found in the Observer's Handbook 2004, pages 137
to 149. This material is also available
on the internet at:
http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2004.html
A lunar eclipse is an astronomical event that can be observed and
appreciated without any optical aid whatsoever, and photographed with
ordinary cameras, though binoculars, a telescope, or a camera with a
telephoto lens can enhance the experience.
The Earth's shadow consists of two parts: the dark central part, where
the Sun's light is completely blocked by the Earth, called the umbra;
and the outer lighter part where only part of the Sun's light is
obscured, called the penumbra. The colour of the eclipsed Moon is
influenced by weather activity along the Earth's terminator: if it is
mainly cloudy, most of the Sun's rays will be blocked and the eclipse
will be relatively colourless and dark; if clear, the light reaching
the Moon will be tinged with sunsets, leading to an orange or red
colour. When the Moon enters the penumbra, the shading is
imperceptible, but darkens as the Moon moves towards the umbra.
In comparison, the edge of the umbra is usually a well defined line,
and it's possible to time when this edge enters and leaves the Moon's
surface, as well as the times when it obscures various craters. Such
timings provide information about the size and shape of the Earth's
shadow in this particular eclipse.
Eclipse times
The eclipse is visible at exactly the same time all across the country,
though local times differ because of time zones. What does differ is the local time at
which the Moon rises. The following table gives times for all the time
zones across Canada, and approximate times of moonrise for each:
Event
|
NDT
|
ADT
|
EDT
|
CDT
|
MDT
|
PDT
|
|
Moonrise
|
Moonrise
|
Moonrise
|
Moonrise
|
Moonrise
|
|
Penumbra 1st contact
|
21:36
|
21:06
|
20:06
|
19:06
|
18:06
|
17:06
|
|
|
|
|
|
|
Moonrise
|
Umbra 1st contact
|
22:44
|
22:14
|
21:14
|
20:14
|
19:14
|
18:14
|
Umbra 2nd contact
|
23:53
|
23:23
|
22:23
|
21:23
|
20:23
|
19:23
|
Greatest eclipse
|
00:34
|
00:04
|
23:04
|
22:04
|
21:04
|
20:04
|
Umbra 3rd contact
|
01:15
|
00:45
|
23:45
|
22:45
|
21:45
|
20:45
|
Umbra 4th contact
|
02:24
|
01:54
|
00:54
|
23:54
|
22:54
|
21:54
|
Penumbra 4th contact
|
03:33
|
03:03
|
02:03
|
01:03
|
00:03
|
23:03
|
Thus, except in western of Canada, the Moon will have risen before
the first imperceptible beginnings of the Moon entering the penumbra.
The Moon will
be above the horizon all across the country when the dark umbra first
touches the Moon. After fourth contact with
the umbra, the reddish shading of the penumbra will gradually leave the
Moon until it is imperceptible at fourth contact.
Observations
A lunar eclipse is one of Nature's most beautiful events, and can be
simply enjoyed for its own sake, whether with naked eye, binoculars, or
a small telescope. In fact, in viewing a lunar eclipse, less is more.
It can also be photographed with all but the simplest cameras. If you
attempt photography, remember to reduce the exposure recommended by
your camera to enhance the colour of the eclipse. If you have any
filter on your lens, even a protective one, remove it to avoid ghost
reflections. I neglected that advice while photographing a lunar
eclipse once, and ended up with a ghost Moon in every shot!
There are at least two kinds of observations which can be made which
are
of scientific value during a lunar eclipse. One is to estimate the
colour and darkness of the eclipse at its greatest extent using the Danjon
Scale of Lunar Eclipse Brightness. This estimate is best done
either naked eye or with low power binoculars. Another is to estimate,
to the
nearest tenth of a minute, the time when individual
craters are eclipsed or emerge from eclipse. Fred Espenak has
provided a table of suitable craters and the approximate time when they
will be covered and uncovered on page 145 of the Handbook; this table is also
available on the web.
Be sure to use Table 4 on this page, as Table 2 refers to the May 4
eclipse. Identifying craters at full Moon is often very difficult
because the lunar surface appears quite different than it does at other
phases. It helps to first identify a few prominent bright craters, such
as Tycho, Copernicus, and Aristarchus, and well defined dark areas like
the Mare Crisium and the Sinus Iridum, and then locate smaller features
relative to them. A simple map, like the one on page 117 of the
Handbook, is actually easier
to use at full Moon than a larger, more
detailed map or atlas. Unfortunately, this map doesn't include some of
the smaller craters in Espenak's list, so you will need to add them
from another map. An ordinary watch synchronized with a time signal or
an accurate computer clock is adequate to record contact times to the
nearest 1/10 of a minute. Because the edge of the Earth's shadow is ill
defined, lower magnifications are actually more useful than high powers
for making these timings, since the shadow will appear sharper. Thus, a
powerful binocular or low power telescope is actually the best tool for
observing a lunar eclipse.
Revised 2004-10-13