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2003年校際火星觀測報告
2003年校際火星觀測報告
獎勵計劃
民生書院
F.3B (28)
許家駿
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Contents
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Introduction
History of “Mars”
The feature of Mars
Data of Mars
The meaning of Mars opposition
Pictures of Mars opposition
Observe the Mars opposition
Conclusion
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Introduction
The Mars opposition in 2003 is a very conspicuous
thing to every amateur astronomer.
Starting from May, many amateur astronomers in
Hong Kong have been pointing their telescopes through
the sky, staying overnight to observe the Mars. During
July and August, more and more astronomers begin to
capture the Mars images. They have been sharing their
experience on their planet imaging, therefore, many
planet masters were “born” after this opposition.
By the way, this opposition also attracts more
people, especially students to realize more about
astronomy. This comes the Mars observation report
award scheme.
This project divides into two parts, the first part is
the introduction of the history and features of Mars.
The second part talks about the 2003 Mars opposition
and how we can observe it.
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History of “Mars”
In Ancient Rome, the Romans
associated the red planet (Mars)
with fire, war and blood. Thus,
they used Mars to represent the
God of War with symbol ♂
(○=shield, ↗ =lance).
In fact, the name of the
month March is derived from
Mars.
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The feature of Mars
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From http://www.the-planet-mars.com/
Olympus Mons
Olympus Mons is the largest
mountain in the Solar System. It
rises 27 km above the surrounding
plain. Its base is more than 500
km in diameter and is rimmed by a
cliff of 6 km high.
It is 3 times the height of
Mount Everest on Earth.
Global Surveyor Image
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Global Surveyor Image
Valles Marineris
Valles Marineris is a system of
canyons with 4,000 km long. It covers
about one-fifth of the circumference of
Mars. Some parts of the canyon run as
deep as 7 km and as wide as 200 km.
Compared to Valles Marineris, the Grand
Canyon on Earth seems quite small with
only 446 km long, 1.6 km deep and 30 km
wide.
Global Surveyor Image
NASA Image
NASA Image
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Polar Cap
Mars has permanent ice caps at both poles composed
of water ice and solid carbon dioxide (dry ice). Mars also
has four seasons same as Earth with similar inclination of
axis. Each season in Mars lasts for 5-6 months.
Global Surveyor Image
North Polar Cap (NPC)
Global Surveyor Image
South Polar Cap (SPC)
Global Surveyor Image
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South Polar Cap (SPC)
Dust Storm
When the range of temperature in Southern or
Northern Hemisphere is large enough, dust storm will
occurs. Mars has many deserts, and its range of
temperature is very large (-140°C-20°C). This causes
the usual occurrences of local dust storms. Moreover,
local dust storms have opportunities to become global
dust storms and they can last for a few months.
Global Surveyor Image
A global dust storm
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Data of Mars
Mean distance from Sun: 1.524 AU
Diameter:
6,792 km
Length of year:
687 days
Rotation period:
24 hour 37 min
Inclination of axis:
25.2°(have four seasons)
Mean density:
真3.95 g/cm³
Satellites:
Phobos and Deimos
S
Inclination of axis: 25.2¢X
Figure 6. Inclination of axis
N
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Satellites of Mars
Phobos
Deimos
•Viking Orbiter Image
Mars is orbited by two small, potato-shaped
satellites, Phobos and Deimos. Their meanings are
terrible and fear respectively. The mean radius of
Phobos is 21 km and 9,380 km far from Mars. Deimo is
much smaller than Phobos, with radius of 12 km and
23,460 km further away from Mars.
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The meaning of Mars opposition
To realize what Mars opposition means, we should
know what an opposition is.
When the Sun, the Earth and a superior planet
form a line, the earth is in the middle between the
sun and the superior planet. This is call “opposition”.
(see figure 1.)
During an opposition, observer on the Earth can see
that the superior planet becomes bigger and lighter.
Therefore, it is the best time for us to observe that
superior planet.
After we have talked about what an opposition is,
we shall talk about the Mars opposition.
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The orbit of Mars is more elliptic than Earth,
therefore, when Mars is in the opposition, its orbit
will have the maximum and minimum distance. (see
figure 2.)
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In general, the Mars opposition occurs in
approximate every 780-days, that is about 25 months.
In normal Mars opposition, the apparent diameter of
the Mars is about 13 to 18 arc second. But the “big”
opposition occurs in approximate every 15-years to
17-years. When it is during a “big” opposition, its
magnitude is up to -1 to -3, brighter than the Jupiter
opposition.
In 2003 Mars opposition, the apparent diameter
of Mars is larger than 25 arc second and the
magnitude is about -3. This is the largest Mars we can
observe since 50,000 years before! Therefore, this
Mars opposition is a rarely one. (see figure 3.)
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Pictures of Mars opposition
2003 Mars Opposition
15 July 2003
1732 UT
1 August 2003
1712 UT
27 August 2003
1618 UT
29 August 2003
1659 UT
CM=262
Dia.=19.29"
Mag.= -1.85
Phase=93%
CM=102
Dia.=22.45"
Mag.= -2.34
Phase=96%
CM=217
Dia.=25.08"
Mag.= -2.97
Phase=100%
CM=217
Dia.=25.07"
Mag.= -2.88
Phase=99.98%
CM = Central Meridian
Dia.= Diameter
Mag.= Magnitude
Taken By Lawrence Hui Ka Chun, Hong Kong.
Celestron 8" Schmidt-Cassegrain Telescope, 2x barlow (double),
Philips Toucam Pro, 1/15 sec, F~40
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From the previous two photos, we can see that the Mars
becomes larger from July to August and it becomes smaller
from September to November.
Besides the size, we can also see a white cap - the South
Polar Cap (SPC) is melting and becomes smaller. The SPC is a
composite of mainly water ice and solid carbon dioxide. 18
Observe the Mars opposition
To observe the Mars opposition, the best
equipment is our EYES. Observation can be divided
into :
• Visual Observation
• Photography
Visual Observation
The definition of visual observation is “using your
eyes to observe”. When you look at the sky, you can
only see a red, bright shinning star and no detail within.
Therefore, we have to use a telescope to observe the
Mars (the diameter of the telescope is at least 3”).
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When you use a telescope with 400x magnification to
observe, the Mars appears as a red disk. There are some
surface details showing up as dark patches and you can also
see the white polar cap. (see figure 4.)
When you look at Mars through the telescope, you
can observe the Northern and Southern Hemisphere. (see
figure 5.) The Southern Hemisphere is dark in colour, the
land is high and many craters within. On the other hand, the
Northern Hemisphere is opposite. It is light in colour, the
land low and many deserts within.
Figure 5. The Northern and Southern Hemishpere of Mars
400x
Northern Hemisphere
(light colour, the land is low,
have many desert.)
Figure 4. Mars under 400x magnification
Southern Hemishpere
(Dark colour, the land is high,
have many craters)
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During visual observation, some equipment may be used:
• High magnification eyepieces (e.g.4mm, 6mm)
• Barlow lens (2x-5x)
• Filters
(red /orange colour filters can increase
the contrast)
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Photography
With the advance of technology, we can now use a
web cam to take planet images.
Doing this kind of digital imaging, we need a
notebook computer, a web cam, a Barlow lens and a
telescope.
Mars take by web cam +8” telescope
Web cam
8” Schmidt-Cassegrain Telescope
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After doing the digital imaging, we have to
process the “raw image” by the computer. This
process will “stack” all images into one single image.
We use a program called “Registax” to do this.
Raw image
(very noisy)
After stacking
Registax
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Conclusion
This Mars observation project has introduced the
followings:– The history of Mars;
– The feature of the Mars;
– The main ideas of opposition;
– The change of Mars during the opposition; and
– The techniques of planet imaging
After this Mars opposition, I have improved the
knowledge in astronomy, especially the technique in
planet imaging. This Mars opposition helps to promote
the development of astronomy in Hong Kong. This
leads more and more people to know about astronomy.
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