SUNSET: 
0
Photographer:
Mark Germani
Location of Photo:
Vancouver, BC, Canada
Date/Time of photo:
24 Aug 2021 · 8 Aug 2022
Equipment:
William Optics ZenithStar 61, Canon EOS 600D (modified), iOptron Skyguider Pro, Optolong L-Pro
Description:
Caroline's Rose isn't in the Messier catalogue, and I became interested in it while playing with long exposures of constellations with my 50mm lens, noticing it as a dense smudge of stars. I first imaged it a year ago while collecting data for the Double Cluster in Perseus, for which I had already rotated my camera 90 degrees. I only collected one hour before the clouds rolled in, so I set it aside to add more time to in the future. I came back to it in 2022. While stacking I noticed satellite trails - oops! I'd forgotten to turn off rejection! I stacked again and blinked between the two stacks and was surprised to see one little red star blinking on and (almost) off. Had I discovered a nova? Nope. WY Cas, an s-type variable star. Neat! I have annotated the image, showing stacks from each separate year. It has a period of roughly 18 months, and my imaging sessions were 12 months apart, so there is a fair amount of contrast in the magnitude. At its brightest, WY Cas is magnitude 7, while at its dimmest it is magnitude 14. It is a Mira variable, and is pulsating due to contraction and expansion. This in turn causes temperature fluctuations, which contributes to the changes in luminosity.
