Hi folks, I was having a go at some HA imaging of the California Nebula (NGC 1499) last night, but only managed 5 x 15 minute subs before the clouds rolled in. However, I stacked the images anyway, and noticed that slap-bang in the middle was a bright asteroid trail. Being a huge fan of asteroid tracking, it's odd that I didn't know it was there beforehand. It turns out that it's Asteroid (584) Semiramis, a 27km-wide object discovered in 1906 which is currently as bright as mag 10.8. I
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