ACTIVITY - OBSERVING THE NIGHT SKY


OBSERVING TIPS 6. Take Your Time The most common mistake among
beginning observers is hastiness. If you are observing an
You will find it much easier to find your way object or a region of the sky, don’t just glance at it and
among the stars if you follow these tips, expect to take in all that there is. Not even an experienced
which are the result of much experience. astronomer could do this. Instead, concentrate on it and,
if what you are observing is large, break it up into smaller
1. Dark Sky. The darker and clearer the regions and observe each smaller region carefully.
more you will be able to see. It is best to leave
the city entirely, but this is rarely convenient 7. DRESS WARMLY
for the majority of people. At the very least,
you should avoid obvious city lights and find 8. Records. Write down or draw everything you observe.
a spot that is as dark as possible. Further- Do not entrust anything to memory. Without detailed and
more, you should try to avoid times of the accurate records, you will not be able to observe the various
month when the Moon is close to being full. changes in the sky that are discussed in this book. Finally,
It is remarkable how difficult a nearly full the process of making a written record will encourage you to
Moon makes observations of faint stars. observe more carefully. Draw diagrams!

2. Dark Adaption. The pupil of your eye Observe the sky for at least 3 hours continuously. (Write
changes its size to regulate the amount of down the times when you begin and end.) Then write a
light it admits. In bright sunshine, the pupil report that is at least 1 page long but less than 2,
contracts to a very small diameter; while at describing (1) what you were able to notice about the sky
night, it opens up very wide to admit as much and celestial objects, and (2) if there were any changes with
light as possible. Unfortunately, it takes time time. Type the paper inlcude your diagrams.
for the eye to become fully adapted to the
dark, and you will not be able to see the You will not need assistance from an experienced observer
fainter stars at first. They will begin to appear who points out “what is what” or tells you what you “should”
after about 5 minutes, and full adaption to be seeing. We don’t want that now; this is to be an un-
the dark takes about 15 minutes to achieve. structured exploration of the sky, emphasizing your
It is amazing how many more stars can be seen impressions. We will have later activities where we are more
when your eyes are fully adapted. specific about identifying the stars according to modern
ideas.
3. Red Flashlight. A bright flash of light
can destroy your dark adaption for many I would prefer that you carry out this activity entirely alone,
minutes; yet you will need to use a flashlight but you may work with up to two others if you feel very in-
to read your star map and make notes from secure about it. You may discuss things you see within
time to time. A compromise is to cover a your group and help each other get ideas. But each of you
flashlight with red cellophane, both to cut down must write his or her own report. If you work with anyone
in its brightness and because red light is less else, give their names at the beginning of your report.
likely to harm your dark adaption. When using
your flashlight, try to keep it as faint as possible Choose an observing location that is as dark as possible,
and to use it as little as possible. and find the best (clearest) horizon you can, uncluttered by
houses and trees. To get acceptable results, you should be
4. Averted Vision Different parts of the able to see at least 20 stars in the sky. To describe the
retina of the eye have differing sensitivities. There location of something in the sky, either use the hand and
is a blind spot where the optic nerve joins the fist techniques described in class, or else use very clear
retina, and there is also a region of maximum phrases like “low in the northeast”, or “midway up from the
sensitivity that you can use by looking slightly to horizon in the SSW”, or “nearly overhead at 9 p.m.”
one side of the object you are observing rather
than directly at it. You can best learn this trick by You will be graded on (1) how many different types of things
experimentation: pick a faint object, and see how you can notice, and (2) the organization of your ideas and
its brightness appears to vary as you look at spots the clarity and coherence of your expression of them and
in its immediate vicinity. (3) the mechanics of your writing: that means your
grammar, punctuation, and spelling!
5. Clouds and Haze Certain types of clouds,
especially a thin layer of cirrus, can be difficult to de-
tect when they appear during an observing session.
Even though the brighter stars are easily visible, the
fainter ones may disappear completely. Thus, you
must be on the alert for changing sky conditions.