Object of the Week March 4th 2018 K 2-1

[obrazell]

Kohoutek 2-1

Auriga

05 07 09.096
+30 49 28.13

Size 2.2'
Mag 13.7 (P)

In 1963 whilst examining the POSS plates Kohoutek came across a number of new nebulae, most of which he was able to identify as planetary nebulae.
These were published in the bulletin of the Czech Astronomical Institute Circular in 1963 as BAICz14. However, in the case of some of the objects he
discovered he was not able to confirm their type. These were listed in his table 2. The object we are interested in here is the first in this list of
questionable objects, K 2-1. Over the years this object has been variously catalogued as an irregular galaxy (UGCA 100), a bright nebula (LBN 809) or
even a reflection nebula (DG 50). SIMBAD classifies this object as a diffuse nebula with notes saying it is not a galaxy or a planetary nebula. This is
somewhat odd as the current professional planetary nebula (HASH) database classifies it as a true planetary nebula. Unfortunately, there have been
no professional studies of this object. In the discovery paper Kohoutek remarks on a blue star near the centre of the nebula at about 18th mag which
could be the central star. Lying in Auriga K 2-1 (PN G173.7-05.8 is thus a somewhat an unusual object. Although it has been imaged for some time there
are not many visual observations of this object. It was popular to observe in the early 90’s but seems to have dropped out of favour since then.
(see Webb QJ 100 for an article on the visual observations up to then). The fact that most of those reports suggest that it responds well to an OIII
filter does suggest that this object is indeed a planetary nebula. It may not be that faint as Kent Wallace reported it was visible in his 8” but I think this
observation maybe an outlier as it is probable that a 12” (30cm) telescope with an OIII filter may be required to see it from good skies. My observations
of it with a 20” show it as an irregular patch which stands out well with an OIII filter. Use of the Wayback Internet archive to try and extract observations
from the long gone, but much lamented, planetary nebula site blackskies.org suggests there is only one observation in its database which I suspect is the
original one from Jack Marling with his 17.5”. There is also a putative cluster here (Skiff J0507+30.8) but it is suggested now that this may merely be an
absorption hole and not a true cluster.

k2-1DSS.jpg

k2-1Pang.jpg

And as always

Give it a go and let us know!!

[Bertrand Laville]

Hi All,

here is my sketch with a 25" Obsession, from Southern Alps, under a not very good sky: SQM 21.36, FWMH 3.8", NELM ~ 6.4v

PK 173-5.1 K 2-1 T635 BL 2010 11 04.jpg

Observation report is here, unfortunately, as usual, written in french : http://www.deepsky-drawings.com/pk-173-5-1/dsdlang/en

Clear sky (which is not the case in Western Europ for the begening of the year )

Bertrand
http://www.deepsky-drawings.com/dsdlang/en/

[Steve Gottlieb]

My last observation was 10 years back with my 18-inch f/4.3 Starmaster at a local site (Lake Sonoma).

18" (2/4/08): K 2-1 was easily picked up unfiltered at 175x as a very large, irregular glow ~2' in diameter, nestled within a group of stars. The NPB filter provided an excellent view with some interior structure and an irregular outline. Appears elongated SW-NE, ~2'x1.5', and brighter and better defined along the edge from the NW to the NE. Several stars are nearby or involved including a mag 12.5 star on the north side. A mag 11 star is off the NE side and two mag 13 stars are barely off the S and SW edge. K 2-1 is situated less than 5' NW of mag 8.2 HD 240736.

I'm curious if others have picked it up unfiltered as I didn't find it difficult.

[Uwe Glahn]

Nice non NGC/IC PN Owen.

With my 27-inch under very good transparency of an High Alpine place but bad seeing because of mountain winds I wrote:
bright, even visible without any filter; very good reaction with [OIII] filter; large, detailed PN; brightest detail is a SE-NW elongated bar through the center, fainter and smaller extensions to the S and N like ears
K2-1.jpg

[Robin]

Hi forum,

With my 12-inch Dobsonian I needed an O-III filter to see this object and I observed it with various magnifications from 49x to 168x. The contrast was highest at 84x magnification, but I could see more details with 168x magnification. The nebula appeared pointy towards an 11 mag star and was situated between two streaks of stars of approximately 13th magnitude. Please find attached my sketch.

Clear skies

Robin

[ScottH]

12/18/22 Kohoutek 2-1
In my 16” at 150x, the possible planetary nebula Kohoutek 2-1 in Auriga is visible without a nebula filter while it becomes terribly bright with one. It’s also visible in my 10” (my notes say with a filter), but this time I tried something different. Seeing how much enhancement it got from using a filter, I excitedly attempted to view it in my 6”. With just 26x and an O-III filter, it was visible!

Now I guess I should try and see it in my 10-inch without a filter, eh?

Scott H.