[Aavso-photometry] Differential photometry for dummies

[R. Brian Potter]

Hi All,
 
I've been reading posts on the AAVSO CCD photometry mailing list for a
couple years now, and finally have taken my first images for submitting CCD
photometry measurements.  I have subtracted a master dark (3-5 images median
combined, depending on exposure time...have not gone to doing flats yet) and
the following is the processing pipeline that I am using:
 
1) Create master dark (done automatically using reduction groups in CCDSoft
v5)
2) Apply master dark to individual images of target field
3) Align individual images after dark subtraction
4) Median combine images to create a single processed image of the field
 
I then use CCDSoft again for the photometry.  For instance, with R UMa I am
using the 9.8 mag standard as the comparison star since it appears to be
closest in magnitude to R UMa, and then the 8.2 mag as the check star.
CCDSoft calculates a magnitude of 8.04 for the check star, and a magnitude
of 10.67 for R UMa.
 
So now a few questions:
1) Is my processing pipeline correct?
2) Since the magnitude of the check star did not come in at 8.2, what do I
do?  How close does it have to be to the published magnitude, and do I apply
a correction to my magnitude for R UMa?
3) How do I compute a SNR using CCDSoft?
4) Anything else I'm missing or doing wrong?
 
Thanks for your patience with a newbie!
 
Brian Potter
Plymouth, MI