A white dwarf star and a red giant are orbiting one another and maybe too close for comfort. The white dwarf siphons off material from the red giant star and developes a dense atmosphere which consists mainly of hydrogen. The newly accreted atmosphere is thermally heated by the hot white dwarf. With this extra mass, gravity increases and the white dwarf becomes compressed which causes it to ignite.
I’ve read that only 10 recurrent novae have been identified. So what I’m following here is quite rare
To get a visual comparison, I’ve been setting up missions to RS Ophiuchi on the same telescope at Slooh and more or less at the same time of night. Cloudy weather was persistent but just as well because the Moon might have been too bright and in close proximity on those cloudy nights.
I did not give up and last night, conditions were perfect and I got a beautiful follow-up image. There’s no doubt, RS Oph is dimming and will go into slumber mode again.
To do an accurate comparison, I have not processed or cropped these images.