[Aavso-photometry] Color change During Period of BZ UMa Superhumps

[Donn Starkey]

I have posted a graph showing the V band photometry of BZ UMa from last night
[Apr 16th] along with the V-R color plot for the same period.  

http://www.starkey.ws/FTP%20Page/BZ%20UMa%20V-R%20Data.jpg

The observations were made from JD 207.54 to 207.75.   The air mass over the
spam of the observation changed form 0.05 to 0.33.  The comp star was
GSC3811-0976 [AAVSO 120 star for BZ UMa].

I have shifted the V-R value 0.7 to the negative so that it is placed close to
the V filtered data on the graph.  The normal V-R value for BZ UMa right now
is about 0.011.  [Sorry ;-)]

There is a subtle 0.03 mag shift to the red as the star approaches ~60% of its
full V brightness.  The then color shifts rapidly 0.03 mag to the red.  It
reaches it minimum V-R value about 7 minutes after V maximum. The color then
continues red and makes a little jump back up toward the blue as the star
attains minimum brightness. 

BZ UMa was dimming at a average rate of 0.24 V mag per day 

==============================================
Donn Starkey
starkey73 at mchsi.com
http://www.starkey.ws
AAVSO Observer SDB  -  CBA Indiana  
VSNET Observing Team  -  MPC Code H63
==============================================