Object of the Week, February 02, 2020 - Two Abell Planetary Nebulae in Orion

[FaintFuzzies]

Object of the Week, February 02, 2020 - Two Abell Planetary Nebulae in Orion – one is easy and other is super tough!

Oh cool, I get this OOTW on Feb 2, 2020. It is a palindrome date and being a football guy, the Super Bowl. Since this date has a bunch of 2s and two great things on this date, I’ll talk about TWO objects but in the same constellation!


Let’s start with the easy one - Abell 12
RA: 06h 02.4m Dec: +09 39’
Size: 37” Mag: 12.0v (central star 19.1)

Many of you know that Betelgeuse is dimmer than usual, almost as “dim” as the belt stars and Bellatrix. It is about mag 1.5. Anyhow, why I’m talking about Betelgeuse? Start from Betelgeuse, hop to the northeast to first star of the club that Orion is holding. Abell 12 is literally sitting right next to the blazing 6th mag star, I mean literally, about 1’ away. Point your scope at the star, toss in an O-III filter, and crank your magnification to something upwards of 300x. Take your time and you will see the high surface brightness round planetary sitting to the northwest of the star (PA 60 degrees). Make sure that your optics are clean as any glare from the star might mask the PNe.

In my 22” I immediately picked it up at 377x as a very bright and obvious round glow with a sharply defined edge. At 528x and averted vision, the surface is slightly mottled.


Abell 12.jpg
Image by Derek Santiago (https://www.pbase.com/dsantiago/image/162322763/large)


Abell12 eyepiece.jpg
Eyepiece rendition with my 22” at 377x and O-III filter under NELM 6.5 skies. Field: 10.4’




Now onto the really hard one – Abell 13
RA: 06h 04.8m Dec: +03 56’
Size: 174x134” Mag 15.3v (central star 18.8)

I believe that the visual magnitude is a bit misleading for this deep red planetary. I tried at least 5 or 6 times before I finally saw this object. I’ve failed under NELM 6.5 to 6.8 skies.

Then one day at a pristine night on Nov 2, 2010 at Shot Rock (elevation 7,800 feet). The skies were very good and fairly steady. NELM was 7.2. Using my 22” and 18mm BGO orthoscopic eyepiece (128x) and Orion Ultrablock filter, I finally observed an extremely faint arc aligned north-south and curving towards the east. The arc was 1.0’ long. Two nearby 15th magnitude stars; one immediately off the north tip and the second star about 0.6’ NNE of the first star. These stars were used to confirm the observation an helps confirm which part of the ring was actually seen. This observation was confirmed by another experienced observer. Then we dropped the 12.5mm BGO ortho (184x) and 10mm ZAO-II (230x). It was seen with both, but a bit tougher with the 10mm as the magnification was a bit too high by that point.


Abell 13.jpg
Abell 13 by Dan Crowson (https://www.flickr.com/photos/dcrows...729568/sizes/l)


Abell13 eyepiece.jpg
Eyepiece rendition with my 22” at 128x with Ultrablock filter under NELM 7.2 skies. Field: 20’


Now let’s “Give it a go and let us know!”

[Raul Leon]

Hi here's my observation 11/4/2013 : Abell 12 planetary nebula in Orion; magnitude:12.4 ; size:37" ; OIII filter works well on this object because it's close proximity to Mu Orionis ; I used a 10mm Ethos at 158x magnification with my14.5 Starstructure Dob f/4.3abell 12.jpg

[lamperti]

With a 20" at 318x in 2010: "Needed the O-III filter and a bit of averted vision to show a nice round distinct glow next to a fairly bright star. It stands out quite nicely with slight averted vision. Direct vision makes it blend in with the brilliance of the star."

[Bertrand Laville]

Hi All,

Here are my sketches of these two PNs, with my 25" Osession, and in an average sky (NELM 6.5, SQM 21.3)
You can have the reports at:
http://www.deepsky-drawings.com/abell-12/dsdlang/fr
http://www.deepsky-drawings.com/abell-13/dsdlang/fr

But, if you are interested on Abell PNs, you can have sketches of all of them, with either 10" or 25", at:
http://www.deepsky-drawings.com/cate...-pn/dsdlang/fr

Clear skies
Bertrand
http://www.deepsky-drawings.com/


Abell 12 T635 BL 2008 03 02.jpg

Abell 13 PN G204.0-08.5 T635 BL++.jpg

[FaintFuzzies]

Thanks Bertrand for sharing your observations. Looks like your brightest section is the same segment that we saw at Shot Rock. And it looks like you picked some extremely faint glow in the middle.

What were your skies like? NELM? (Opps re-read your post, you listed it at 6.5). I was looking at your sketch for the data and not your post)

Clear skies,
Alvin

[Uwe Glahn]

Nice couple Alvin. Honestly I have to admit that I don't have a clear positive observation of Abell 13. It's for sure one of the hardest PN of the catalog. I copy the notes from Abell PN project below.

Abell 12
4", 154x, [OIII], fst 7m+
with higher magnification the small round disk is easily visible and cseparateate easily from the glow of mu Ori, no ring structure visible

4,5", 110x, [OIII], fst 6,4
amazingly easy with [OIII] and higher power, round, structureless

8", 160x, [OIII], moon (54%)
despite moon and bad seeing visible as direct vision object directly NW of mu Ori; round glow without ring structure

16", 230x, [OIII], fst 6m6
positioned in the direct neighborhood of the 4mag star mu Ori, only with [OIII], round disc, difficult ring structure

16", 450x, [OIII], fst 6m8
needs at least UHC filter, better view with [OIII], sharply defined, SW part little brighter
Abell12.jpg

Abell 13
16", 129x, [OIII], fst 6m8
NW-part of the PN popping out in and out of view, can not hold it with averted vision, unsure observation

20", 62x - 121x, [OIII], fst 6m5+
very difficult observation, nothing to see with lower magnification, with 121x and [OIII] a saw very faint nebula the position of the brighter NW part, without filter there are a few 15mag stars exactly at this position, with filter I'm not sure whether stars or nebula

27", 105x, [OIII], NPB, fst 7m+
PN only 13' S of 5,6mag bright 66 Ori; with narrow field eyepiece, [OIII], NPB filter and 6,6mm AP an extremely faint glow is suspected at the position of the brightest part at the W border of the PN; glow can not be hold with averted vision; uncertain observation despite 27" aperture and very good transparency

[obrazell]

I am intrigued by Bertrand's observation of Abell 13 with an OIII filter as this object has almost no OIII emission when you look at its spectrum. It is almost all in the red end of the spectrum.

Owen

[Bertrand Laville]

Hi Owen,

This is a very interesting remark.
When we used to say "OIII", this is not enough precise; we should say "OIII with red lines" or "OIII without red lines".
Concerning "my" OIII, the answer is at: http://www.deepsky-drawings.com/moye...res/dsdlang/fr
For instance, you should have a look at: http://www.deepsky-drawings.com/sh2-276/dsdlang/fr

Hope this could be useful for all of us
Bertrand
http://www.deepsky-drawings.com/