Transcript Astronomy and Space Science

Astronomy and Space Science I
Dr. Hoi-Fung Chau
and
Dr. Alex Tat-Sang Choy
Jointly Organized by
Hong Kong Space Museum
HKU Physics Department
Co-organized by
CDI of EDB
Astronomy and Space Science
• Astronomy Basics
– Length, time, angles
– Celestial sphere, star maps
• Solar System
– Orbital Motion of the Earth around the Sun
– Geocentric models
– Heliocentric models
– Modern views
• Q&A
Length: Power of Ten
Length (m)
Approximate length of object
100
102
104
107
109
1011
1013
1016
1018
1021
1022
1024
1026
Meter rule
Length of track
Distance between Shatin and Tai Po
Diameter of the Earth
Diameter of the Sun
Orbital radius of Earth
Current distance to Eris and Sedna
Distance to nearby stars
Size of Omega Centauri
Size of Andromeda Galaxy
Typical distance between galaxies
Size of a typical supercluster of galaxies
Size of observable universe
Units of Length
• 1 ls = distance light travel in 1 second = 299792485 m ≈ 3x108 m
• 1 ly = distance light travels in 1 year ≈ 9.46x1015 m ≈ 1016 m
• 1 AU (astronomical unit) = mean distance between the Sun and Earth ≈
1.49x1011 m
• 1 pc (parsec) = distance from which 1 AU extends 1 arcsec ≈ 3.26 ly ≈
3.24x1016 m
• 1 Mpc = 106 pc ≈
3.26x1022 m
Examples
Name
Type
Diameter
Distance
Distance (m)
Moon
Sun
Io
Sirius
Pleiades (M45)
Polaris
Orion Nebula (M42)
M4
Crab Nebula (M1)
M54 (extragalatic)
Ring Nebula (M57)
Andromeda Galaxy
satellite
star
satellite
star
open cluster
star
diffuse nebula
globular cluster
supernova remnant
globular cluster
planetary nebula
galaxy
0.012 ls
4.7 ls
0.012 ls
7.9 ls
20 ly
140 ls
30 ly
70 ly
6 ly
300 ly
1.8 ly
1.4x105 ly
1.3 ls
500 ls
2100-3100 ls
8.6 ly
380 ly
430 ly
1500 ly
7200 ly
6300 ly
8700 ly
2300 ly
2.5x106 ly
3.8x108
1.5x1011
6.3-9.3x1011
8.2x1016
3.6x1018
4.1x1018
1.4x1019
6.8x1019
6.0x1019
8.3x1019
2.2x1019
2.4x1022
Time Scales
Duration
Approximate Time Scale of Event
1 ms
1s
1 day
1 month
1 yr
10 yr
102 yr
103 yr
104 yr
107 yr
1010 yr
1011 yr
Rotational period of certain pulsars
Time between successive heart beats
Rotational period of the Earth
Orbital period of the Moon
Orbital period of the Earth
Orbital period of Jupiter
Orbital period of the Uranus
Age of the Crab Nebula
Time since last ice age
Lifespan of some high mass stars
Age of the universe
Cooling time of white dwarf
Angles
• Angles are measured in degree (°), arcmin ('), arcsec("); radians (rad, or no unit).
• 1° = 60' = 3600"
• 1 rad = 180°/π ≈ 57.3°.
• Small angle approximation:
angle = arc length/distance
• The apparent diameter of
the Sun and the Moon are
about 0.5°.
• Resolution limit of a 4"
telescope ≈ 1".
• Note: Do not confuse
arcsec with inch, both use
the same symbol.
Objects with Large Angular Sizes
(roughly to scale)
Sun, 30’.
Andromeda Galaxy (M31)
180’ x 63’.
Orion Nebula (M42), 85’ x 60’.
Moon, 30’.
M54, extragalatic
globular star cluster, 12’
Pleiades, open star cluster, 180’.
M4, globular star cluster, 36’
Ring nebula,
planetary
nebula,
1.4’ x 1’.
More Examples
Crab Nebula
Supernova
remnant,
6’x4’.
Io, Jovian
satellite, 1”.
Polaris A’s apparent size = 0.002”.
Polaris A to Polaris Ab is 0.2”;
Polaris A to Polaris B is 20”;
Polaris A to Dubhe ≈ 30°.
Hubble Deep Field, ≈ 1.5’.
Celestial Sphere
• The celestial sphere is a hypothetical sphere centered at the center of Earth.
• On the celestial sphere, stars are fixed, while the Sun and the planets moves
slowly.
• The celestial sphere rotates, thus most stars rise and fall daily.
• The celestial poles and celestial equator are projections of the poles and
equator on the Earth on to the celestial sphere.
Useful Relations
• Altitude of north celestial pole = latitude L
• Local zenith forms an angle 90°-L with the north celestial pole
• Local zenith forms an angle L with celestial equator
____
zenith
Star Maps
• Star maps show the sky East-side West, because it is
intended for looking up. There are 88 constellations.
• Brighter stars are shown with bigger dots. Many star
maps also mark the location/type of deep sky objects,
multiple stars, and the Milky Way.
The Solar System
Source: NASA
Motion of the Sun on Celestial Sphere
• Axial tilt of Earth is 23.44° ≈ 23 ½ °.
• Different parts of the sky are in the
glare of the Sun in different months.
Vernal equinox (春分), autumnal equinox(秋分) are the points at which the Sun passes
the celestial equator, while summer solstice(夏至) and winter solstice(冬至) are the
northern and southern extreme points of the ecliptic (黃道).
Ecliptic Plane
• the ecliptic plane is the plane in which the Earth orbits.
• the ecliptic is the circle form by the ecliptic plane intercepting the
celestial sphere
Planetary Motion on Celestial Sphere
Planets usually moves on the celestial sphere from east to west (prograde motion)
near the ecliptic; while sometimes moves from west to east (retrograde motion).
Motion of Mars in 2003 and 2005. Time step=10 days.
Pictures from NASA.
Geocentric Model of Planetary Motion
(Apollonius, 260-190 BCE)
• Explains qualitatively the prograde and retrograde motions, and
brightness variation.
• Motion planets around epicycle centers and epicycle centers around the
Earth are uniform circular motions.
• Note: the centers of epicycles for Mercury and Venus always align with
the Sun, which explains their maximum elongations (29° and 48°).
• Ptolemy (90-168 CE) modified this model to be quantitatively accurate
compared to the observations of the time. His model was used for 1400
years until the Renaissance.
Heliocentric Model of Planetary Motion
(Copernicus, 1473-1543 CE)
• In the heliocentric model, the Earth and other planets orbit the Sun.
• The prograde and retrograde motions are apparent effects due to
relative motions of the Earth and the planets.
Advantages of the Heliocentric Model
• The heliocentric model of Copernicus is not intrinsically more accurate.
• Calculation is easier with the Copernicus model.
• Copernicus was able to determine the orbital radii (relative to Earth orbit) of
all six planets, while in Ptolemy model the lengths are incorrect.
• Heliocentric models predict stellar parallax, while geocentric models predict
otherwise.
Further Developments
• A schematic heliocentric model is
shown on the right. The heliocentric
model would later be a great help to
Kepler (1571-1630 CE) in finding his
laws of planetary motions empirically.
• Later Newton (1643-1727 CE) gave the
model a firm physical basis using law
of gravity and motion would
• Stellar parallax, hence distance, was
first measured in 1838 (Bessel).
• In Copernicus’s theory, the Sun is at the
center of the universe, while the Earth
is merely a planet.
• We now know that Sun is just one of the stars in one of the galaxies (Milky Way
Galaxy) in one of the group of galaxies (Local Group) in one of the superclusters
(Virgo/Local Supercluster) in the universe.
Modern View of the Solar System
–
–
–
–
–
Sun
Terrestrial planets
Asteroids
Gas Giants (outer planets)
Trans-Neptunian Objects
(TNO)
• Kuiper Belt
• Scattered Disc
• Oort Cloud
(hypothetical)
– Comets
• Note: Dots represent objects.
Someone looking at the solar
system at this scale shouldn’t
see asteroids and the Oort
cloud with naked eyes. Much
of the Solar System is empty
space.
Beyond the Solar System (Hierarchy of Objects)
[pictures from atlasoftheuniverse.com]
Solar Neighborhood
Orion Arm
Note: nebulae are usually in spiral arms.
Milky Way Galaxy (2-4x109 stars)
Note: globular clusters (105-106 stars) orbit the
galactic core as satellites.
Beyond the Milky Way [pictures from atlasoftheuniverse.com]
Local Group (30+ galaxies)
Virgo Supercluster
(100 groups/clusters of galaxies)
Neighboring Superclusters
(100 superclusters shown)
Visible Universe
(107 superclusters)
* visible ≠ whole
but not visible has no
physical relevance.
In Depth Questions
Q: What is a constellation?
A: The IAU divides the celestial sphere into 88 constellations (regions) with
precise boundaries (yellow dashed lines in the figure).
More:
Each star belongs to exactly one
constellation.
The term “constellation” is also less
formally used to describe a group of star
visibly related to each other in a pattern,
such as those connected by green lines in
the figure. However, in such a scheme,
some stars such as Sirrah in Andromeda,
may be considered as both the head of
Andromeda or part of the Square of
Pegasus. Also, stars not connected by
patterns still need to be assigned a
constellation.
Q: How does the coordinate systems on the Celestial
sphere look like?
A: As shown on the graph: the longitude and latitudes of the Celestial sphere are
called RA (right ascension) and DEC (declination). DEC runs from +90° to -90°.
RA runs from 0 to 24 hours. Each hour has 60 minutes, and each minute has 60
seconds, just like the clock. The RA of zenith of a fixed location increases by
roughly 1 hour for every hour in time.
(Note: Do not confuse the
minute with arc minute which is
1/60°, both measure angles.)
Refer to the previous figure, the
light blue lines are RA and DEC
lines.
Q: Where exactly is the center of the celestial sphere?
A: The center of the celestial sphere is the observer. In other words, each observer
has a celestial sphere.
More:
The celestial sphere is a device used to represent the direction of celestial
objects for observation. For example, someone in Beijing would see the
Moon’s position a little differently from someone in Hong Kong, due to
parallax of the observing locations. Therefore, it only make sense to have a
different celestial sphere (and the objects on them) for each for observer.
Another example is the satellite or space station, which, due to there close
distance from Earth, depends greatly on the location of the observer. Also, if
one were to observe from Mars, it would not make sense if the celestial sphere
is centered on Earth!
Note however that in most situations, we are observing on the Earth and most
objects are far away so it is convenient to set the center of the Earth as the
center of the celestial sphere.
Q: I heard that the definition of the ecliptic plane has
been changed, is it?
A: Yes, but for all purpose in this course, the change has no real effect.
More:
• A very first definition is the ecliptic plane is the plane in which the Earth
orbits.
• A few amendments have been made since then.
• In 2006, the IAU adopted a new definition:
– the ecliptic pole is explicitly defined by the mean orbital angular
momentum vector of the Earth-Moon barycenter in an inertial reference
frame.
• This change is to better agree with dynamical theories, however, the actual
change in value is extremely small.
• As a result the Earth’s orbital plane is very slightly different from the
ecliptic plane.
Q: What’s the relation between solar motion and the
calendar?
A: The Sun’s position relative to Vernal Equinox is important for determining
the seasons and the calendar. A major function of the calendar was for
agriculture.
More:
• Solar motion on the ecliptic is not uniform (due to the Earth’s elliptical orbit),
hence seasonal lengths are different.
• The mean tropical year, i.e. the mean duration for the Sun to pass though the
same point on the ecliptic twice, is 365.242 190 419 days (epoch 2000).
• A good approximation is 365 + 97/400 = 365.2425 days. This leads to 97
leap years in every 400 years (Gregorian calendar). The rule for assigning
leap year is: leap years are all years divisible by 4, except for those divisible
by 100 but not 400. E.g. 1900, 1999 are not leap years; 1996, 2000, 2004 are
leap years.
• A less accurate approximation is 365 + ¼ = 365.25 days. This leads to a leap
year in every 4 years (Julian calendar). But in the order of hundreds of years,
the calendar will become less accurate. This approximation, however, is
convenient for many estimations.
Q: How was the Sun/Earth orbit modeled by Greek
astronomers?
• A: Seasonal lengths are sensitive to the Sun’s motion, therefore the nonuniform motion of the Sun was discovered early. In Hipparchus model, the
Earth is shifted off-center of the deferent. This point is called the eccentric.
Effectively, this model approximates the Kepler ellipse and area laws.
• More:
– Using the length of seasons
(i.e., time taken for the Sun to
pass between equinoxes and
solstices), Hipparchus found
parameters to his model, which
agreed well with observations
until Tycho/Kepler’s time.
– Note that the length of seasons
changes over time, due to
precession of the equinoxes.
However, eccentricity does not
change.
Q: What is the cause for precession of the equinoxes?
A: Precession is caused by the torque applied by the Sun, the Moon, and the
planets. The torque is the result of the gravitational pull on Earth’s equatorial bulge.
More: The lower left picture explains the effect due to the Sun. The lower right
picture shows the 26000 year period precession of the north celestial pole.
Pictures from Wikipedia.
Q: What is a day anyway?
A: A (solar) day is the duration for the Sun to pass the meridian twice.
More:
• The celestial sphere rotates about 360.9856° daily, i.e. it takes about 23 hr 56
min for stars to go around in a circle. In other words, stars rises 4 minutes
earlier each day. (360/365.25 ≈ .9856, 24x60/365.25 ≈ 3.94).
• As a result, the Sun passes the meridian (highest) at the approximately same
time each day. For Greenwich, it is 12:00pm; for HK, it is 12:24pm.
Q: Can you give some example of planetary events?
A: Some events are:
• Conjunctions (合):
– Two objects closest from Earth’s
point of view
• Stationary (留):
– When the ecliptic longitude
(sometimes RA) do not change
• Greatest elongation (大距):
– Approximately the best time for
observing inferior planets
• Transit (凌日) of inferior planets across the Sun:
• Mercury: …, 11/1999, 5/2003, 8/11/2006 (during sunrise in HK),
5/2016, …
• Venus: …, 12/1882, 6/2004, 6/6/2012 (visible in HK), 12/2117, …
• Eclipse (蝕) of Sun or Moon.
• Similar events in the Jupiter system.
Continue…
• Opposition (衝):
– Best time for observing superior planets
– For Mars, opposition occurs approximately every 2.14 year. Due to higher
orbital eccentricity (0.093) and smaller semi-major axis (1.52 AU), the EarthMars distance varies between 0.66 and 0.38 AU (1.52×(1 ± 0.093)–1), giving
large size and brightness variation at opposition.
Great opposition of Mars (near
perihelion) (火星大衝) occurs every
15-16 years. The one in 2003 was the
closest in 60,000 years, which the
media made a big deal of. However,
as shown on the graph, the other great
oppositions such as the 1988 one are
not much further away.
Note: since great opposition occurs
near perihelion, when Mars is the
hottest, planet-wide dust storms could
occur, so observe early.
Picture: C.F. Chapin, http://www.astromax.com/planets/images/mars2003.gif
Q: What is Aristotle’s model of the universe?
A: See figure.
• Aristotle’s (384-322 BCE) model placed the superior planets in right order
using their speed on the celestial sphere.
• It explains simple phenomena
such as daily rise and set of
celestial objects, but not the
details in longer time scales.
• In this model, the Earth is at
the center the universe,
surround by water, air, fire,
etc.
• As more were known about
the planetary motion through
observation, ancient
astronomy would transform
slowly to a qualitative science,
then a quantitative science.
Q: What does Ptolemy’s geocentric model look like?
A:
• The epicycle is used to explain
prograde/retrograde motion
• The epicycle center rotated
uniformly about equant E,
instead of the center of deferent
M.
• The Earth is located off-center at
the eccentric.
• Distances EM = MO.
• This is the geocentric model that
agrees quantitatively with
observations of the time. From
the time of Apollonius to Ptolemy,
planetary theories changed
gradually from qualitative to
quantitative science.
Q: Ptolemy model looks quite different from Kepler’s,
why did it work so well?
A: Ptolemy was approximating Kepler’s law, without knowing it.
More:
• The reasons are:
– the elliptical orbits of the planet are
close to a circle
– the eccentric takes the role of a
focus, approximating Kepler’s first
law
– Ptolemy’s equant has the effect of
approximating Kepler’s second law
• Using Tycho’s data, Kepler refitted
Ptolemy’s model, which gave a
maximum error of only 8’ for Mars.
• Since uncertainty for Tycho’s data is
only 1’, Kepler was forced to give up
the circles.
Equant
Eccentric/Sun
Comparing the elliptical orbit of
Mars (red) to a circle (blue).
Q: How to transform between geocentric and heliocentric
models?
• The two models are equivalent if constructed as shown. The vectors pointing
from the Earth to the planet are always the same between the two models.
• Copernicus used his own observation as well as Ptolemy’s data to obtain
parameters to his model.
• The precisions of the two models are the roughly same.
Earth
Sun
Q: One arcmin is about the size of a HK$1 coin in 88 m away,
how did Tycho Brahe achieve this accuracy without telescopes?
A: Great care for accuracy, a whole lifetime of pursuit, and a lot of support.
More:
– He was the first one to notice the problem relating observation accuracy
and have the ability to improve on them. He improved the sight with a slit
design, and also added gradual scale to improve reading. Very large
instruments help measuring smaller angles, but they requires stronger
materials and mechanical parts. To support Tycho’s work, the King of
Denmark granted him the estate of the island Hven, on which he built
world’s best observatory called Uraniborg.
D=3 m
Left: The sight’s aligned horizontally if
the star can be seen just on the CBGF
edge and ADHE edge at the same time.
The vertical alignment can be found
similarly. For solar alignment, sunlight
is allowing to pass thru the hole in the
front and fall on a circle drawn on the
ABCD plate.
Q: Did Galileo really invented the telescope?
A: No. But Galileo did designed and made his own telescopes, and improved on
them. He was ahead of others by a few months in telescope quality, enough for
him to claim most of the discoveries.
• More: A typical Galilean refractor had a plano-convex objective lens with
30-40 inches focal length; plano-concave eyepiece of focal length about 2
inches focal length. It was good enough to discover Lunar features, Jupiter’s
four moons, phase of Venus, as well as sunspots.
• (Note: He became blind in his last years, due to observing the Sun directly
through the telescope without proper filter or projection.)
Galileo’s telescopes are quite
unimpressive by today’s standard,
with 0.5-1 inch effective objective
aperture, about 15-20x power, and a
very narrow (15’) field of view, not to
mention significant aberrations. But
they were the best at the time.
Q: Was Galileo jailed?
A: He was found guilty in his trial and sentenced to jail for life. However, his
treatment was closer to house arrest. He worked and published during this time.
More:
Some ideas Galileo held, such as the Earth moves around the Sun, the celestial
bodies are not perfect, the Bible was not meant to teach science, etc., were
considered heresy at the time. A less fortunate astronomer named Giordano
Bruno was burned at the stake. To understand why Galileo was treated leniently,
perhaps one should understand that Galileo was well known not only to those
who practice science, but to influential people of the society and even to the
Church. He made many discoveries such as the law of motion, measured
gravity, invented a thermometer, studied the pendulum, etc. The physics taught
at the time stress qualitative arguments, Galileo however believed in the
importance of mathematics and experiments. He was thus called the “father of
modern science”. What made him stand out from other scientist of his time,
was the skill of mixing of theory and practice. Galileo was also very successful
in getting supports from many people. Although there were people who refused
to even look though the telescopes, Galileo succeeded in introducing the
telescopes to many nobles and military officials who quickly understood the
practical and military applications of the telescope.
Q: Does the discovery of phase of Venus disproves the
geocentric theory?
A: No. Models, such as Tycho’s model, which require the Venus and Mercury to
revolve around the Sun give the correct phase of Venus.
Q: What is a planet?
A: Definition by the International Astronomical Union (IAU) in 2006:
(1) A planet is a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so
that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) has cleared the neighborhood around its orbit.
(2) A “dwarf planet” is a celestial body that satisfies, (a) and (b) but not (c), and
is not a satellite.
(3) All other object orbiting the Sun, except satellites, are called “Small Solar
System Bodies”.
More:
Since some recently found “minor planets” are similar in size or even bigger (Eris)
than Pluto, there was a need for redefinition. The new definition is based on
planetary formation theory that, given enough time, a large enough object would be
able to collide with or scatter away objects and dominate its orbit. The redefinition
has been criticized and remains controversial. Note also that the line between (2)
and (3) is left for later meetings. For many small object, the hydrostatic equilibrium
condition (b) is not easy to test.
Q: After the invention of telescope, how was position/angle
measured?
A: First by using wired micrometer eyepiece, then by measuring photographic plate.
More: The wired can be moved to match the star’s position. In some other
eyepieces, a patterned glass is placed at the focus for reading out data. Angles can
be measured from a photographic plate using the focal length and the lengths
measured on the plate.
Q: We’ve been focusing on the development of the West,
what about the work of Chinese?
A: Ancient Chinese astronomers developed sophisticated tools to observe the
positions of celestial objects. Unfortunate their work did not affect the western
astronomy development much.
More: As an example, the drawing on
the right shows an invention in the
Song Dynasty. The main instruments
(red, blue, and yellow) are driven by
water-powered gear systems to
simulate Earth’s rotation and tell time
automatically.
Source: HK Science Museum,
星‧移‧物‧換
Q1: Was Copernicus the first to think the Earth moves around the
Sun?
Q2: Did Copernicus model have epicycles?
A: Q1: No. Q2: Yes.
More:
• Ancient Greek and Indian astronomers had proposed heliocentric views.
However, Copernicus model was the first to have the good length, time, and
angle parameters. It was the reasonably close to modern model of the Solar
System.
• In Copernicus model, the epicycles are used to account for elliptical orbits;
where as Ptolemy’s epicycles are used to account for Earth’s motion.
• Since the full Copernicus model is rather complex, the simplified heliocentric
model is usually presented to students. This toy model does not have
epicycles, but in practice, it has almost no predictive value.
Q: What are the true advantages of the heliocentric model?
A: Easier to compute, correct orbital radii, predicts stellar parallax.
More:
• For those who computed using hand and tables, his simplification was much
appreciated. Therefore, it was accepted first as a computational method rather
than a physical model of the cosmos, even for those who are not willing to
take a view different from the Church.
• Attempts to measure the distance to the planets were not successful at the
time. In the geocentric models, the radii of deferent and epicycle of a planet
are not obtained from observations (angle and time), only their ratios. Since
the radii of planetary epicycles are the same as Earth’s orbital radius in the
heliocentric model, Copernicus was able to determine the orbital radii
(relative to Earth orbit) of all six planets.
• Heliocentric models predict stellar parallax, which is exactly why Tycho did
not accept the heliocentric model. He could not observe parallax for stars,
which are much further then he thought, and have a much smaller parallax
(<1”) than he could measure.
Q: What is the role of human/Earth in cosmology?
A: It has been decreasing since history.
More:
Here are some paradigm shifts:
• Earth is the center of the universe
• Earth is slightly off the center of planetary orbits. (Ptolemy)
• The Sun is the center of the universe
• The Sun is one of the stars in the Milky Way Galaxy
• The Milky Way Galaxy is just one of the galaxies
• The universe has no center
• We are not even made of the dominant form of matter (see
nonbaryonic dark matter)
• The universe is made up of more energy (in the sense of E/c2) than
matter (see dark energy).
Q: How can I understand different designs of telescopes?
A:
Q: Can you suggest some equipments for schools?
A: Different schools have different needs due to their programs, location,
budget, number of students, etc. It is important to know if the equipments
are for visual or imaging work, or for inspiration. The following are just
some possible equipment choices, popular in the amateur astronomy
community, and are benefited by cost saving due to mass productions:
Small high quality refractors with small equatorial or alt-az mounts: best image
quality, very versatile, most expensive. A compromise is to have a small one for
portable and frequent uses. Good for planet/solar/lunar visual observations, wide
field imaging. (Front Solar filter required for solar observations thru the
telescope.)
Medium size catadioptrics with GOTO mounts: reasonable price, reasonable
image quality, but a bit low in contrast and have narrower field, very powerful
when combined with a GOTO and tracking system. Good for high power
imaging or general purpose visual observations.
Large reflectors with dobsonian mounts: cheap for the size, good image quality,
but no tracking. Their large sizes allow observation of dimmer objects.
Continue…
Eyepieces: a set of high, medium, and low power eyepiece for each scope is the
minimum. Quality is important for high power eyepieces, while good wide field
low power eyepieces are also quite expensive. There are many good and low
cost medium power eyepiece. Some company sells a set of eyepieces which
could be a low cost way to start with. Neutral density moon filter.
Binoculars are low cost, very useful, and can be given to students no using the
telescopes. Note: DO NOT distribute binoculars for solar/day time sections!
Solar projection screen. FRONT solar filter.
Cooled CCD cameras with high quality optical and tracking systems can take the
best DSO (deep sky objects) pictures, but are very expensive. Some cheap
CCD/CMOS based webcams are very good for taking videos of planets for
stacking, as well as class demonstration. Digital cameras with proper adaptors
can take good stack-and-track images for planets and bright DSO.
In recent years, binoviewers have become very cost effective. Experience has
show that their views are very effective for attracting the attention of the
untrained eyes. Recommended if budget allows.
Q: Can you give us some references?
A: Here are some of them:
•
•
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•
•
•
•
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•
NASA. The NASA site contain many useful information and images.
Wikipedia. Note: The Wikipedia is probably the quickest way to find
information. However, because it can be edited by anyone, one should not trust
the information without checking independent sources or risk getting wrong or
misleading (intentional or not) information.
HKU Physics Department, Nature of the Universe web site
http://www.physics.hku.hk/~nature/
J. M. Pasachoff, Astronomy: From the Earth to the Universe (1998).
E. Chaisson and S. McMillan, Astronomy Today (2005).
M. A. Hoskin, Cambridge Illustrated History of Astronomy (2000).
J. Evans, The History & Practice of Ancient Astronomy (1998).
蔡國昌 和 葉賜權 , 恆星 (2000).
葉賜權 , 星‧移‧物‧換 (2003).
香港太空館小學天文敎材套 (2000).
Q: Are there any useful classroom teaching kits available?
• A: Here are some of them.
• Cosmic Voyage DVD is a good film to introduce the
powers of ten approach to study the structure of the
universe.
• Models of celestial sphere. Ideally, one can use a big one
to teach (but it costs about HK$4,000) and use a few small
ones (that can be brought a few hundred dollars each) for
students to play in class.
• Free software such as www.stellarium.org can be used to
simulate the motion of celestial bodies, to set exam
questions and to plan your observation session.
Sources of Pictures in this Talk
Sources of pictures: Pictures are obtained from the following sources unless
given next to the pictures.
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NASA. The NASA site contain many useful information and images.
Wikipedia. Note: The Wikipedia is probably the quickest way to find information.
However, because it can be edited by anyone, one should not trust the
information without checking independent sources or risk getting wrong or
misleading (intentional or not) information.
HKU Physics Department, Nature of the Universe web site
http://www.physics.hku.hk/~nature/
J. M. Pasachoff, Astronomy: From the Earth to the Universe (1998).
E. Chaisson and S. McMillan, Astronomy Today (2005).
J. Evans, The History & Practice of Ancient Astronomy (1998).
C. M. Linton, From Eudoxus to Einstein: A History of Mathematical Astronomy
(2004).
Dr. Richard Hennig