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!!