The story so far – SAO 84015

Flitting through a planetarium program I stumbled upon a nice bright Carbon star in Corona Borealis.  Designated SAO 84015 at magnitude 6 this should look really great!  So a couple of nights ago I fired up the mini-WASP to grab this one, 5-minute subs, all 3 cameras.  First sub came down and – nothing.  No bright star near the centre of the field of view at all.  Strange.  Never mind, I just left the mini-WASP running as I have done this sort of thing before where I’ve been a little off in pointing the scope.  Next day I process the data – and – still nothing.  Open up the planetarium program and compare with my image – I find SAO 84015 on my image and it is sitting there at about magnitude 14??  So now we start to go deeper.

A bit more investigating shows that SAO 84015 is much more well known as R Coronae Borealis (even I have heard of that before) which shows odd “inverse nova” behaviour.  I knew that it often dimmed from mag 6 to mag 14 but after a few weeks or at most months at minimum it would slowly climb back up to mag 6 again.  Could I have been plain unlucky and caught it at its minimum?  Start digging again.

Looks like R Coronae Borealis took a dive around 2006 – surely it hasn’t been at minimum all this time has it?  It has never shown that behaviour before.  Contacted a few star experts and – yes – that’s exactly what’s happened.  R Coronae Borealis took a dive all those years ago and is still languishing down at mag 12 – 14 with no immediate signs of recovery, how weird.

So now I’m playing a waiting game, waiting to see if and when R Coronae Borealis once again blazes away at mag 6.  If I can get another image with the star at maximum this will make a really interesting image pair – what a huge contrast in star brightness!!


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