LUNAR ECLIPSE PROJECT
WHAT IS AN ECLIPSE OF THE MOON (LUNAR ECLIPSE)?
An eclipse occurs when a hypothetical straight-line can be drawn through the centres of the
Sun, the Earth and the Moon (i.e. they all line up).
Solar eclipses occur when the Moon in its orbit around the
Earth passes between the Sun and Earth (Sun – Moon – Earth),
with the shadow of the Moon falling on the Earth (new moon).
Lunar Eclipses occur when the Earth lies between the Sun and
the Moon (Sun – Earth – Moon) and the shadow of the Earth
falls on the Moon (full Moon).
More details are available at http://www.mreclipse.com/Special/LEprimer.html
The times for the 4th April 2015 Lunar Eclipse is tabulated below in AEST.
Note: NSW & Vic are still on daylight savings time (AEDT add 1 hour).
Event
UTC Time
Time in QLD
Visible in QLD
Penumbral Eclipse begins (P1)
4 Apr at 9:03 AM
4 Apr at 7:03 PM
Yes
Partial Eclipse begins (U1)
4 Apr at 10:17 AM
4 Apr at 8:17 PM
Yes
Totality begins (U2)
4 Apr at 11:58 PM
4 Apr at 9.58 PM
Yes
Maximum Eclipse
4 Apr at 12:00 Noon
4 Apr at 10:00 PM
Yes
Totality ends (U3)
4 Apr at 12:03 PM
4 Apr at 10:03 PM
Yes
Partial Eclipse ends (U4)
4 Apr at 1:44 PM
4 Apr at 11:44 PM
Yes
Penumbral Eclipse ends (P4)
4 Apr at 2:58 PM
5 Apr at 12:58 AM
Yes
Note that totality is only 5 minutes.
PROJECT 1 - HOW DARK IS THIS ECLIPSE?
BACKGROUND INFORMATION
The darkness of the eclipsed Moon depends on several factors. The first is how deep into
umbral part of the shadow (dark grey in the diagram below) the Moon passes.
For example; if the Moon passes through the centre of the Earth’s umbral shadow, the
eclipsed Moon will be “dark”, and will remain totally eclipsed for a longer period of time (up
to 1 ½ hours).
If the Moon passes through the outer
edge of the umbral shadow (see
diagram beside), as is the case for this
lunar eclipse (ratio of only 1.01), then
the eclipse is said to be “bright” and
the Moon is totally eclipsed for a much
shorter period of time (5 mins).
Other factors that affect the darkness
of the Moon include the transparency
of the Earth’s atmosphere. That in
turn depends on the amount of cloud
and the amount of dust in the region
of the atmosphere where the Sun’s
light just skims past the Earth. It has
been noted in the past that dark
eclipses occur after periods of volcanic
activity where the air is laden with
volcanic ash.
For this eclipse, the Moon passes through the outer edge of
the umbral shadow (darkest region), meaning that it is a
“bright” eclipse and is “totally eclipsed” for only a short
period of time (approx. 5 mins).
There is a standard scale of the darkness of eclipses called the Danjon Scale tabulated below:
http://www.mreclipse.com/Special/danjon.html
Danjon Scale of Lunar Eclipse Brightness
Danjon Value
𝑳=𝟎
𝑳=𝟏
𝑳=𝟐
𝑳=𝟑
𝑳=𝟒
Description
Very dark eclipse.
Moon almost invisible, especially at mid-totality.
Dark Eclipse, grey or brownish in coloration.
Details distinguishable only with difficulty.
Deep red or rust-coloured eclipse.
Very dark central shadow, while outer edge of umbra is relatively bright.
Brick-red eclipse.
Umbral shadow usually has a bright or yellow rim.
Very bright copper-red or orange eclipse.
Umbral shadow has a bluish, very bright rim.
ACTIVITY
1. Estimate the Danjon Number during the period of totality (i.e. 𝐿 = 0 to 𝐿 = 4).
2. Estimate a 𝐿 number to 1/10th of 𝐿, e.g. get an answer like 𝐿 = 3.2. Note the time and
get as many independent estimates as you can – get friends and family to join in but don’t
tell them of your estimate so their estimate is ‘independent’.
3. Find the averages and trends as a later exercise.
4. Share your findings with others (see email addresses at end of document)
PROJECT 2 – PHOTOGRAPHY OF THE ECLIPSED MOON.
There are many ways to photograph an eclipse of the Moon.
Look at the following links:
http://www.landscapeastrophotography.com/tips-for-photographing-the-blood-red-moonduring-a-total-lunar-eclipse/
http://www.nikonusa.com/en/Learn-And-Explore/Article/h1sctsrv/How-to-Photograph-aLunar-Eclipse.html
ACTIVITY
Using a tripod and a DSLR Camera (preferably fitted with a 300 mm lens), take several digital
images during the partial and totality phases of the lunar eclipse. These images can be posted
on the Student Journal Discussion Board and compared with other student’s results.
For the best images, make sure the
image is not saturated, i.e. over
exposed or burned out. Some
cameras have a display of the
distribution of brightness of the
image, such as in the diagram
beside.
The little peak at the ‘light’ end of
this histogram tells us that some
part of the image is saturated.
To avoid saturation, you may need to reduce the exposure time (the time that the camera’s
aperture is open). We need the light producing the image spread relatively evenly across all
the histogram, not like the example in the diagram.
PROJECT 3 – ESTIMATING THE DIAMETER OF THE MOON.
Using the moon as a “screen”, we can see the shadow that the Earth cast onto it.
Below are some links to experiments to determine the size of the moon from the size of the
Earth’s shadow.
http://resources.yesican-science.ca/eratosthenes/moon.html
http://www.umich.edu/~lowbrows/astrophotos/alway/lunareclipse.html
ACTIVITY
a. Whilst looking at the Moon during the partial (penumbral) part of the eclipse, estimate
the size of the Earth’s shadow relative to the size of the Moon.
Use the web experiments to determine the size of the Moon given that the diameter
of the Earth and the Sun is 12 756.2 𝑘𝑚 and 1 391 684 𝑘𝑚 respectively, and the
distance to the Sun and the Moon is approximately 149 600 000 𝑘𝑚 and
384 400 𝑘𝑚 respectively.
b. Using photographs of the partially eclipsed Moon, do the same experiment, but this
time by drawing the size of the Earth’s umbra on a photograph and then estimating
the relative size of the umbra and the Moon. Use the above dimensions for the Solar
System to get the size of the Moon.
c. Share your findings with others (see email addresses at end of document).
PROJECT 4 – ESTIMATING THE DISTANCE TO THE MOON.
We can determine the distance to the Moon by using a parallax method. Parallax is when a
distant object appears to be in a different place (i.e. to have moved) when viewed from two
different places separated by a significant distance. Here is an example:-
From place A, the tree C appears to be near to the other tree, and from place B it appears to
be in front of the house.
For example, if we get a photograph of the totally eclipsed Moon from a town in mid NSW
and another from Far-North Queensland (i.e. two locations separated by a significant
distance), we will see that the Moon is in a different star field (i.e. the background stars appear
in different positions).
If we are able to measure the angular difference of the location of the Moon against the
background stars in the two photographs taken at the same time from the two locations, and
if know the distance between the locations where photographers were taken, we can
determine the distance to the Moon using some simple mathematics (simple astrometry).
ACTIVITY:
Take photos of the totally eclipsed Moon with a field of view large enough to capture the
background stars in the sky near the Moon (a 300 mm lens is good enough for this activity).
You will be able to compare your images with others taken from a different location. To find
the separation distance between two locations you can use Google Earth.
Things to note:
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The photos should be taken at maximum zoom and for an exposure time that shows
both the Moon (not over exposed – saturated – burned out – see above) and some
stars in the image.
The photos need to be taken as close to mid-totality as possible. For this eclipse this
will be at 11:00 pm in NSW and 10:00 pm in Queensland (± 2 mins).
Be sure that the camera lens is adjusted to its best focus.
Check the exposure of the photos as the Moon approaches and starts totality. The
exposure time may need to be increased as the Moon dulls.
An analysis can be performed after the eclipse once photos are received from the other
participating locations. Send an email to the addresses at the end of this document to receive
advice on how to do this.
PROJECT 5 – PLOTTING A LIGHT CURVE OF THE ECLIPSE
As the eclipse progresses, the brightness of the Moon will change. This will be noticed as the
Moon gets darker and then lighter again as the eclipse progresses. This change can be
represented in a “light curve” graph.
A light curve graph is the plot of the Moon’s brightness verses time. On the next page is a
light curve plotted using data from a previous eclipse.
ACTIVITY
The aim of this activity is to measure the brightness of the photographic images of the Moon.
Again, it is important that the images of the Moon are not saturated and should be taken at
maximum zoom. To obtain the data in order to plot a light curve similar to that above, these
non-saturated images need to be taken at approx. 10 min intervals across the entire time of
the eclipse – i.e. the full 6 hours of it!!!
Each image will need the time it was taken and the exposure time recorded. Most DSLR
cameras automatically record this information on the ‘header of the image’.
To make sure that the time is correct, take a photo of an accurate clock at some time during
the night – the computer screen will do if the computer clock has been checked. Alternatively,
keep a record on a piece of paper.
Instructions on how to analyse this data to compile a light curve can be made available in a
separate document after the eclipse event by emailing the addresses below.
NOTE
High school students studying Senior Astronomy through TSAA and members of
an Astro Club in Wagga Wagga NSW are keen to exchange images and
information. If you would like to participate, send your images/information by
email to:
[email protected] and [email protected].