Interesting find, Vic! Following your lead, I took the ratio of the following night to that night to see how variable Beta Tau was between those two nights. I aligned sidereal times by taking only the ratio when the star was at the same altitude. Here is the resulting MS Excel file:
http://nightskylive.net/temp/BetTau040917.xls
The ratio led to the following plot:
Several conclusions can be drawn. First, no variation for Beta Tau was evident between the two nights. The average variation was only 0.01 magnitudes, very small by common photometric standards. Over the whole night, the average variation was about 0.001 magnitudes -- a fantastic demonstration of stability that can perhaps be used for significant scientific utility.
Next, HL (Haleakala), the CONCAM station that took the data, takes excellent data! The level of photometry from night to night is better than expected. The HL site itself is a good site to be able to have so similar an atmospheric transparency between two nights.
- RJN
