Surprisingly, no notice seems to have been taken in this R CrB subsection of this forum of Z UMI's latest decline. Nevertheless and I suppose not unexpectedly given its circumpolar location, observer coverage of the decline has been good. The decline began about the opening of May while as of late Z UMI gives indications of having bottomed-out at 15th magnitude and begun a recovery.
I just added this star to my observing program in May. Since my largest scope is only 6", my last observation at 12.6 was as faint as i could go given my observing conditions here. I will be keeping an eye out in the coming weeks if i get a break in the weather.
Both R Crb and Z Umi seem to have bottomed out. R Crb, for a while, looked like it was on its way back to mag 6, but never made it... it got to 7.5 or so. Then it dropped off the cliff to almost mag 13. Coming back a bit on data that I got from an observation last night (7/3/15). New data on Z Umi as well. I've been getting photometric data from a very nice telescope system and posting the results on these two for a while.
R Crb hasn't been at mag 6 since 2007.
I can get down to about mag 18 with some difficulty. Relatively low s/n and limited comp stars at that brightness.
Interesting stars to watch because they're so unpredictable.
Bill - PWD