I’ve been trying to measure the transform coefficients for my outfit. A few days ago I took some images of the two standard fields Melotte and SA32 on the same night and using the same kit. The graphs I get look ok however I get slightly different slopes for the two standard fields. For example the graph for (B-V) against (b-v) has slopes of 0.9324 for Melotte and 0.8501 for SA32. If I try to plot all the points together I get two straight lines with an offset between them. Similarly for the other two plots (B-V) against (B-b) and (B-V) against (V-v). The lines look like pretty good straight lines. Any suggestions would be appreciated.
Steve,
Did the airmass differ much between the two sets of images?
Roy
Thanks Roy, I didn’t think of that but in fact the airmass for one was 1.17 and the other 1.38.
Steve