1/3
Astronomy Homework # 1
Name_________________________
DUE: Friday, January 22 (by 11 PM)
Your homework grade depends not only upon your getting the correct answer but also grammar, spelling
and punctuation, particularly in questions that require explanations. Numerical answers to questions do
not need to be written in complete sentences and you should show your work where ever it is
appropriate. Partial credit may be given for showing your work even if your result is incorrect. You will
also be graded on the use of significant figures, proper units of measure and proper scientific notation.
You may work with others in determining the answers to the questions, but what you write should be in
your own words – any homework assignments that look too similar to that of other students will receive
no credit. Unless otherwise noted, all questions are worth 1 point. Homework can be turned in at the
office Latham 121 during business hours, during class, or on-line at e-Learning.
1. (6 points total) How many significant figures are in the following numbers?
a.
32.0700
b. 0.003207
c.
2.09 x 105
d. 9.1 x 10-12
e.
0.0030
f. 5.00
What are the answers to the following problems? Put your final answer in scientific notation if
appropriate. Make sure your answers are given correctly following the guidelines for significant figures.
g. (3.8199 x 10-6) x (2.80 x 107)
h.
i.
3 . 8199  10
2 . 80  10
6
7
( 3 . 8001  10
4
)  ( 2 . 0  10 )
4 . 215
j. (2.9)4
k.
0 . 33
5 . 03
l. 7.02 – 7.0 x 7.0 + 7.0 /7.0
6
2/3
2. (5 points total) The small angle formula, S = 0.0175 R  relates three quantities, the actual
size/diameter of an object (S), the object’s distance (R), and the angular size of the object (). S and R
are measured in the same units of distance while  is measured in degrees.
The Moon has a diameter of 3480 km and is located, on average, 384,000 km from the Earth.
a. (2 points) What is the angular size of the Moon, as seen from the Earth, when it is at this average
distance?
b. (2 points) The Sun has nearly the same angular size () as the Moon. Using the value you got in part
‘a’ and the fact that the Sun is on average 1.50 x 108 km away from the Earth, what is the actual
diameter of the Sun?
c. The Moon is slowly moving away from the Earth. How will this change in distance influence the
angular size of the Moon over a long period of time?
3. (2 points) If you are in Cedar Falls and you see an object that is 21.5° above the southern horizon
along your meridian, what is the object’s declination? Cedar Falls’ Latitude=42.5° N.
3/3
4. (2 points) If you are at Rotorua New Zealand (Latitude 38° S) and there is an object with a declination
of 7° N, how high above the horizon is this object when it is on your meridian? Which horizon is it
located closest to?
5. At what time of day would the First Quarter Moon set? Limit your answers to one of the following sunrise, noon, sunset, midnight.
6. At what time of day would the Full Moon be highest above the horizon (on your meridian)? Limit
your answers to one of the following - sunrise, noon, sunset, midnight.
7. If you saw the Moon rising at 8:35 PM, what phase is it?
8. If you saw the Moon on your meridian at 10:45 AM, what phase is it?
9. If the Moon sets at 10:30 PM today, approximately at what time will it rise in one week?