Astronomy 122 First Homework Assignment
This assignment reinforces what we did in class. You may work
on this assignment with up to 4 other people if you like.
In this homework you will be measuring stars as well as
signal-to-noise in the background for two situations.
Each simulation has only two stars in it. You should make
observations of duration 1,2,4,8,16,32 and 64 seconds.
To measure the brightness of the star place a small box (the
green one by convention) over the star and the similar size
red box over a region of the background that doesn't contain
a star (easy to do in this case since there are only two stars
in the field). Remember the brightness of star is the difference
in counts between the green and the red box. For this excercise
you need to difference the boxes labelled total counts. Measurments
should be made in a box of size 10x10 pixels (type in 10 in the
Sample Size window and hit enter for it to be accepted).
For each simulation make 3 measurements of each star for each
exposure time and do the following:
- Record your data for star brightnesses for each exposure
time.
- Calculate the signal-to-noise ratio of the background for each
exposure time. This ratio is obtained by dividing the values displayed
in the box labelled mean by the values in the box labelled standard
deviation.
This should be done on the values in
the red box (e.g. the box without the star in it).
After doing this measurements, answer the following questions.
- Why are the measurements of the stars at longer exposure times
more reliable than the shorter exposure measurements?
- What is the essential difference in observing conditions between
the two simulations?
- If you change increase the exposure time by a factor of 4
(e.g. compare the 2 second one with the 8 second one, or the 4
second one with the 16 second one), how much does the signal-to-noise
improve? Does this suggest a relationship between signal-to-noise
and exposure time?
Email the above to rdrummon@darkwing.uoregon.edu
First Simulation
Second Simulation