Group Quiz
==========

Compute the final "ZF" image based on the following inputs:

bias     1  3
         2  1
     
flat    42 58
        61 28
     
object  14 15
        10 21

You should absolutely feel free to collaborate on this homework!!!

Task #1
===========================
Measure the mean and standard deviation (i.e., "sigma") of the counts in the individual bias frames from our practice dataset. 

Task #2
===========================
Measure the mean and standard deviation of the counts in the master bias from our practice dataset.  What is the ratio of these two types of standard deviations (from Task #1 and Task #2)?

Task #3
===========================
Measure the mean and standard deviation of the counts in the *sky regions* of frame a045.  How do they compare to those found in Task #2?

Task #4
===========================
Measure the brightness (in magnitudes) via photometry on 5 field stars
in frame a045.  See the attached for the particular 5 field stars.
Use the PHOT package within noao/digiphot/apphot.  Remember the
following commands:

spacebar -- do photometry
:ap  X   -- change aperture to X
:ann Y   -- change inner sky annulus to Y
:dan Z   -- change sky annulus thickness to Z

To do PHOT within IRAF, you'll prefer to have your desktop focus-follow-the-mouse.