With a friend we are running a nova survey (called Dauban Survey) since April 2012. It is briefly described here: www.aspylib.com .
Since September 2012, we detected the variations of >500 known variable stars, and we have measured at least one data point for each one of them every week. I expect the number of variables will easily rise to a few 1000s in the next year. I hope we will have a good coverage of some Mira curves. Observation of known variables is not the primary goal but we would like if possible to submit the data to AAVSO.
At the moment I am going through the description of the "extended format" for submission, and try to see which format we could use. I have a few questions:
1) the system we use is a refractor 80/600 + CCD ST8300 + filter Astrodon exoplanet (cuts everything below 500nm).
We cannot use a standard photometric filter because we loose too many photons and we cannot spend too much time on a given field, in average we observe > 400 fields every night. The Astrodon filter is interesting because it cuts the blue part of the spectrum which is the most variable. The calibration is done with R magnitudes from USNO-B1 catalog (I know it's not the best one but that's the one we use for the astrometric reduction..).
My question is: what kind of filter should we indicate in the AAVSO extended format ? I guess CR is not correct because we have a filter. I see the possibility to indicate O = other filter but it does not seem to be recommended ?
2) for the magnitude calculation we use an ensemble photometry method. We have a fixed set of about 150-200 reference star for each field. We measure the magnitude constants (difference between USNO-B1 magnitude and instrumental magnitude = 2.5*log(flux)) for all these stars. We use the median of all the magnitude constants for our calibration. Using the median allows to remove the outliers and possibly a few variable stars. In principle the method should be very good. So far we did a few comparisons with other softwares and observers, and everything seems quite ok.
Here is my problem: for submission using the ensemble photometric method, I read that AAVSO requests a check star: http://www.aavso.org/aavso-extended-file-format 
I don't know how can we find such check stars. If we pick up stars randomly, then I am sure, just by statistics we will pick up a few ones which vary. My impression is that adding a check star may be a source of error. Will the data be accepted without check star ?
Thanks for your help