Possibly Visible Supernova Remnant Candidate in Canis Major

[ScottH]

This ones for you, Uwe (my deep-sky brother), since if you hadn't started the thread SNR G206.9+2.3 in Monoceros, I still wouldn't have seen that SNR in my 16-inch!

About 1 degree northeast of Delta Canis Majoris is a 11'-wide planetary nebula known as FP J0711-2531. Apparently, on HASH, it was discovered and classified as a planetary nebula, but is now considered to be more likely a supernova remnant. I'm looking forward to trying for it in my 16-inch and, like a lot of objects I seem to become aware of at the tail of the said object's observing window, am a touch upset I didn't learn of it a few month earlier.

Here is the image that (today) I first stumbled upon it. And here is Peter Goodhew's image of it, showing that an O-III filter should be of some us!

You know I'm going to have to take a shot at it after the moon leaves the evening sky...

Scott H.

[ScottH]

On HASH, in the notes section to FP J0711-2531, Quentin Parker wrote "Large, wispy/filamentary, approximately round PN candidate or SNR; spectrum has [NII]~0.8H-alpha, [SII] strong ~0.6H-alpha, but low density; [OIII]>H-beta;[OII] in far blue and [OI] in red; In area of wispy MIR emission. Possible faint, extended NVSS radio emission. No evidence of blue CSPN in PANSTARRS g-band. Deep amateur narrow-band images by Peter Goodhew in January 2021, see: https://www.astrobin.com/dkpzwh/. Is also a possible Supernova remnant as spectrum also has [OI]6300,6363 and has filamentary type structure and possible extended radio emission. Needs more data."

On 4/16/23, I was using a 36" f/5.1 dobsonian and looked for it as soon as it was dark. With filters and 150x, it was visible mostly north of a binocular bright star. I could see it about the same with either O-III or NPB filter. Not being used to the field of view (just 31'), I was surprised at how well it fit into it. Round, diffuse glow. Wasn’t easy, but a confirmed sighting.

Now it just needs to be confirmed as a SNR!!

Scott H.


CMa SNR.jpg

[Robin]

Hi Scott,

Congratulations!! This seems to be the first visual observation ever of this nebula!? It mus feel like climbing a mountain for the first time. :-)
You wrote that it wasn't easy with 36". So would you estimate that it is invisible with 20"? I was thinking about giving it a try next season, but it is quite low above the horizon at my location.

Clear skies

Robin

[ScottH]

Hi Scott,

Congratulations!! This seems to be the first visual observation ever of this nebula!? It mus feel like climbing a mountain for the first time. :-)
You wrote that it wasn't easy with 36". So would you estimate that it is invisible with 20"? I was thinking about giving it a try next season, but it is quite low above the horizon at my location.

Clear skies

Robin

Good question. I would say that it should be 20-inch visible from my latitude (36.1N) and under my skies (best nights 21.6mpsas). I mean, I don't have a 20-inch, but you can bet I'm going to try for it in my 16-inch. I truly do think I have a shot. Observing through a 36-inch might sound impressive, but this one has big chips in the primary mirror, a light shroud that only goes halfway in circumference, a star-diagonal, and is under 21.2mpsas skies. So I like to think that if I had Steve Gottlieb's 24-inch at my place, I'd see just a much/faint.

Scott H.

[ScottH]

Okay, Robin, I've looked at FP J0711-2531 twice now this winter and twice I saw it with an O-III filter. The second time was a few nights ago and it was distinct in my 16-inch with an eyepiece yielding 60x and a 6.8mm exit pupil. A little harder to see at 100x, but still there! Below is Peter Goodhew's O III image and I've circled what I saw.

Scott H.

oiii-for-jpeg_orig.jpg

[Robin]

Hi Scott,

That's a cool observation! This object is still on my list. I've only experienced 5 clear nights after October, so the backlog of planned observations is quite huge now. :-)

Clear skies

Robin