The Left Arm of Cepheus (287 hrs)

Image Title: The Left Arm of Cepheus (287 hrs)

Copyright: Copyright: Jeffrey Horne

Date image was taken: November 08, 2023

Location: Nashville, TN (Bortle 8)

Image Description and Details: The Left Arm of Cepheus (287 hrs)

This area of Cepheus doesn't get a lot of attention. There's no Elephant Trunk nebula, no Bat or Squid nebula, no Wizard nebula, no Iris Nebula. So naturally, I wanted to take some time and get a really deep integration on it, to try for a unique view.

Maybe the most interesting thing in this photo is the small blue blob of Oiii (with a sharp Ha/Sii arc) that's about 20% over from the left side of the image, and about a third of the way up from the bottom. At some point during data acquisition, the Oiii just started showing up. I thought it was dust in my imaging train, but after re-taking my flats, the Oiii was still there. Jaša Rebula was able to figure out that the area had been cataloged as supernova remnant Te 12.

Jaša looked a little deeper and found that there wasn't Oiii noted for Te 12 in the HASH database.

Drew Evans then imaged it a longer focal length to verify that the Oiii was present. Sure enough, it's there.

We also found a very hot white dwarf in the Oiii signal, so we think that Te 12 might be misclassified as a supernova remnant, and might actually be a planetary nebula. On November 12, 2023, we submitted it to the relevant authorities for clarification and classification.

I've tried to email Phillip Teutsch (the namesake of Te 12) to let him know about this Oiii blob. I tried emailing a couple of his known colleagues as well, but nobody seems to have a current email address for him. If anyone knows how to get in touch with him, please let me know.

A BIG shoutout to Brian Fulda, Drew Evans, and Jaša Rebula for teaming up to figure out what this little blob of Oiii actually is.

Acquisition details:
Antlia 3nm Narrowband H-alpha 2": 1143×300″(95h 15′) -10°C
Antlia 3nm Narrowband Sulfur II 2": 1161×300″(96h 45′) -10°C
Chroma OIII 3nm Bandpass 2": 1141×300″(95h 5′) -10°C
Total integration: 287h 5′

Equipment Details: Imaging Telescope: William Optics Redcat 61
Imaging Camera: ZWO ASI2600MM Pro
Mount: ZWO AM5
Filters: Antlia 3nm Narrowband H-alpha 2", Antlia 3nm Narrowband Sulfur II 2", Chroma OIII 3nm Bandpass 2"
Software: Adobe Photoshop, Aries Productions Astro Pixel Processor (APP), Pleiades Astrophoto PixInsight, ZWO ASIAIR

Website or Facebook Profile: http://facebook.com/jeffreyhorne