Download Astronomy 321 --- Homework Exercise: Star Wheel

Astronomy 301
HOME OBSERVING ASSIGNMENT
Fall 2014
As a part of this course, you will be observing the night sky outside of class on a regular basis, and keeping a
log of your observations (see p. 3). Following is a list of constellations, stars, asterisms, and other objects
that you should learn to identify this semester. They are grouped according to where they can be found in
the sky in the early evening in early fall. Be sure to take advantage of clear nights early in the semester to
become familiar with the night sky! This should be done by practicing with your star wheel at home. Keep
in mind that the locations of the constellations will vary depending on the time of night you observe.
In the tables below, the first column is the constellation, with its standard 3-letter abbreviation in
parentheses. For constellations with bright stars, one or two of these bright stars are listed in the 2nd column
and should also be learned. The 3rd column lists other objects of interest (e.g., star clusters, nebulae,
galaxies) that you should also know how to locate. A quiz on this material will be given once we’ve had a
few clear nights. Remember, since labs meet only once a week it’s very important to practice at home!
1. Looking north
Stars within about 38° of the North Celestial Pole are “circumpolar” from San Francisco. They are close
enough to the pole to be visible throughout the year (though are easiest to find when they are highest).
The principal constellations in this region are:
Ursa Major (UMa)
Ursa Minor (UMi)
Cassiopeia (Cas)
Cepheus (Cep)
Draco (Dra)
Polaris
asterism: Big Dipper; “pointer stars”; Mizar & Alcor
asterism: Little Dipper
2. Looking up
One of the most prominent asterisms of the summer and fall sky is the “Summer Triangle.” The Summer
Triangle is defined by the brightest stars in the first three constellations listed below. The other two
constellations are smaller and fainter but are in the same region of the sky as the Summer Triangle.
Lyra (Lyr)
Cygnus (Cyg)
Aquila (Aql)
Sagitta (Sge)
Delphinus (Del)
Vega
Deneb (“tail”) Alberio (“eye of the swan”--nice double star)
Altair
3. Looking south
In the summer and early fall the constellations that are visible to the south include those in the direction of
the center of the Milky Way galaxy, and the southern-most part of the zodiac. From west to east, the
constellations are:
Libra (Lib)
Scorpius (Sco)
Ophiuchus (Oph)
Sagittarius (Sgr)
Capricornus (Cap)
Antares (“rival of Mars”)
asterism: teapot
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4. Looking west
The following constellations are visible in the early part of the semester but will be below the horizon after
sunset later on. Be sure to learn them early, before they’re gone! Use the handle of the Big Dipper to “arc
to Arcturus” and “speed on to Spica.” This will help you orient yourself to this part of the night sky.
The keystone of Hercules can be found by making a line between Vega and Arcturus. The “keystone” is
1/3 of the way from Vega to Arcturus, along that line.The brightest star in Corona Borealis is 2/3 of the way.
Bootes (Boo)
Arcturus
Virgo (Vir)
Spica
Hercules (Her)
Corona Borealis (CrB)
Coma Berenices (Com)
asterism: “keystone”; M13 (globular cluster)
5. Looking east
The following constellations are rising in the east in the evening in late summer and early fall. Later in the
semester they will be higher overhead during the lab time. The last three constellations in this group contain
mostly faint stars, so are challenging (usually just barely visible) from San Francisco. Develop confidence
in the first four before you try the rest.
Pegasus (Peg)
Andromeda (And)
Perseus (Per)
Aries (Ari)
Triangulum (Tri)
Pisces (Psc)
Aquarius (Aqr)
asterism: Great Square of Pegasus
M31 (nearest spiral galaxy to the Milky Way)
Algol (“demon star”, an eclipsing variable star)
6. Winter constellations
The following constellations are not visible in early fall during the lab time. They come up later in the
evening at this time of year. Later in the semester they will be visible during the lab time. Start learning
these as soon as you get a chance. They contain some of the brightest stars of the night sky.
Auriga (Aur)
Taurus (Tau)
Orion (Ori)
Canis Major (CMa)
Canis Minor (CMi)
Gemini (Gem)
Capella
Aldebaran
Rigel & Betelgeuse
Sirius
Procyon
Castor & Pollux
M45 (Pleiades star cluster); Hyades star cluster
M42 (Orion Nebula, a giant star-forming region)
7. Constellations of the zodiac
Most of the constellations of the zodiac are listed in the groups above. These are constellations whose
defining area includes a portion of the ecliptic (apparent path of the Sun). For completeness, here is the full
set, including the “13th”, Ophiuchus, from west to east (the direction of the Sun’s apparent motion). All will
be visible at some time during the semester, with the exception of Leo (unless you stay up late).
Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini,
Cancer, Leo
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KEEPING YOUR OBSERVING LOG
This homework assignment will be on-going throughout the semester. You are required to keep a neat,
hand-written log of the observations that you make on nights other than lab nights. They can be made from
your home, from the SFSU campus (including the observatory, on open nights but not during lab sessions),
or anywhere else you like. To make these observations, at least at the beginning, you will need to have your
star wheel handy (and possibly a flashlight, preferably covered with red cellophane or a cloth).
You should aim to make one set of observations per week on average, spending 20-40 minutes or so on the
observations.
Don’t forget to allow time for your eyes to adjust to the night sky (10-15 minutes at least). Each night that
you record an observation, record the following in your log:
(1) Date, time and location of your observation.
(2) Weather and lighting conditions, including the presence or absence of the Moon, and its phase.
(3) What constellations, asterisms, stars, and/or planets you attempted to locate.
(4) What you succeeded in locating, and any techniques you found helpful in the process and/or any
difficulties you encountered.
(5) What you noticed about any of the objects (e.g., colors of stars and/or planets, twinkling or lack
thereof, brightness of a planet relative to nearby stars, patterns that helped you find things, etc.).
SUBMITTING YOUR OBSERVING LOG
You will be asked to submit your log for review and grading a few times over the course of the semester.
Here is how to prepare your log for submission.
(1) Xerox or scan the parts of your log book that contain the observations you made (do not submit
the log book itself).
(2) Make a cover sheet with your name and a summary of the observations you made (one line per
observing session, including date and location).
(3) Staple everything together and turn it in to me in class on the due date.
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