Hello! I rechecked my transformation coefficients last night. I obtained the firsts set of coefficients about 4 months ago using M67 and some Landolt standards on a single nights run. The values were

B = 0.179 V = -0.039 I = -0.017 and B-V = 1.227

Over the last two nights, I rechecked the coefficients using about 30 Landolt standard stars spaced every 15 degrees from 30 degrees to 90 degrees. The coefficients were the same when calculated on each individual night and when combined.

B = 0.140 V = -0.038 I = 0.016 (positive while the previous value was negative) B-V = 1.043

The results seem close. Are they close enough so that I would consider my system stable for 4 months, or should I obtain transformation coefficients on shorter intervals? If these look fine, can I increase the time between transformation coefficient checks?

Thank you and best regards.

Mike