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deepskytraveler
October 21st, 2015, 03:23 AM
Object of the Week October 18, 2015 – NGC 2022

NGC 2022, PK 196-10.1, PN G196.6-10.9
Constellation: Orion
Type: Planetary Nebula
RA: 5h 42m 5s
Dec: +09° 05’ 11”
Size: 22” x 17”
Mag: 11.7
Central Star Mag: 14.9
Mean Surface Brightness: 18.7 mag/arcsec2

A certain harbinger of the winter season in the Northern Hemisphere is the sight of the constellation Orion in the southeastern sky. Although Orion is a winter constellation which doesn’t transit the meridian until January, I have found the autumn months to be an ideal time to observe it as it rises during the early morning hours; the time when the skies are often at their steadiest and light pollution the least impactful. Not to mention that the outdoor temperatures are much warmer in October than in January. So it was earlier this month in just such a situation, I turned my 15” f/4.5 reflector to Orion and quite accidentally came across NGC 2022, until that moment unknown to me.

After conducting a literature search through observing guides and handbooks, then researching this object on the web, it is safe to say that NGC 2022 is a lesser known, if not an obscure object. Why I’m still not sure, but it isn’t because of its magnitude of 11.7, or even its mean surface brightness of 18.7. It is a bit small, however it takes to high power quite well particularly under the best sky conditions.

William Herschel discovered NGC 2022 on December 28, 1785. In his discovery notes he records for H IV-34: “Considerably bright, nearly round, like a star with a large diameter, like an ill-defined planetary nebula.” Indeed NGC 2022 is a planetary nebula.

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NGC 2022’s shape is a prolate spheroid (like an American football) which is surrounded by a spherical shell of fainter matter. The planetary nebula’s characteristics place it rather early in its evolutionary cycle. At a distance of approximately 8,100 light-years the true physical extent of the its central ring measures approximately 0.8 x 0.6 light-years, while the much fainter outer ring measures 1 light-year in diameter. The HST image of NGC 2022 shows remarkable structure within the planetary. This dynamic structure is attributed to “interacting winds”, i.e., the interaction of different temperature gases.

1822

Also visible in the HST image is the central star with a nominal magnitude of 14.9. The 1988 paper "Magnitudes of central stars of planetary nebulae" by Gathier and Pottasch (http://adsabs.harvard.edu/full/1988A%26A...197..266G) gives a visual magnitude of 15.92, though also refers to the earlier results of 14.9 and 14.8. That's a pretty large discrepancy. In any case, a magnitude like this is always going to be misleading based on the bright background of the nebula.

Locating NGC 2022 is easy - it lies in a prominent part of northern Orion just 1.8 degrees southeast of the 3rd magnitude star Meissa (Lambda Orionis).

With my 15” at 214x, under heavily light polluted skies (SQM 18.98) and less than average transparency I saw NGC 2022 easily. My notes reflect that I found the planetary to be surprisingly bright, nearly circular in shape, having a ghostly appearance with uniform brightness throughout, other than a smidgen of brighter circumference in one small arc, strong hint of bluish tint, no inner structure visible, central star not visible. Tried 286x with no significant differences observed.

A survey of observing reports on the web reflects observations in scopes ranging from 5” to 48”. In the smaller scopes the planetary takes on a stellar appearance and can easily be missed. Once located it can be detected at low power. In Deep Sky Companion: Hidden Treasures, Stephen O’Meara says: ”At 60x, the nebula is a very small, pale gray, and highly noticeable disk, nicely condensed; it truly look like a distant gas-giant planet.” At 282x in a 5” scope O’Meara can start to detect structure within the core. Another observer with a 13” scope under exceptional transparency and seeing reports: “A truly great night 100X--obvious dot. 220X--pretty bright, pretty small, little elongated 1.5X1 in PA 0. There is no central star at 220X. 330X--some difficult structure is seen, mostly averted vision only. The east side is consistently brighter than the west side. There are brief glimpses of a stellar spot offset to SE. All this detail is at the limit of the 13". The central star is never held steady, averted vision helps it to stand out and it is seen about 30% of the time at high power.” It seems to require scopes of 18” or larger and high power to ferret out structure in the nebula. Detecting the central star is even more challenging it seems. Though aperture is certainly an enable, it is the overall sky conditions that will make or break the observation of the central star

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Now it is your turn to chase NGC 2022. You have plenty of time and hopefully many opportunities this observing season to catch the brightest planetary nebula in Orion.

As always,

"Give it a go and let us know!
Good luck and great viewing!"

wvreeven
October 21st, 2015, 05:24 AM
I observed this planetary nebula with my 6" telescope on January 22, 2007, at 50x and 170x. At 50x I needed an OIII filter to identify it. At 170x I could see it was a small disk. OIII didn't help at this magnification.


Clear skies, Wouter

hajuem
October 21st, 2015, 10:44 AM
Hi Mark
Thanks for your perfect Presentation of this object!

I've observes this object on January 2014 with the 16 inch. Here the drawing result:
1825
Filter: --// v= 520x// fst 6m3// Seeing very good
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520x mit UHC

CS Hajü
www.astromerk.de

KidOrion
October 21st, 2015, 03:47 PM
This was the last object I took notes on this year--all the way back in January! (Between miserable weather, moving cross-country, and classwork, it's been an awful observing year.)

MOON: 28 days, absent
SEEING: 7 (was forecast to be poor)
TRANSPARENCY: 8, later 7
NELM: 5.2
WEATHER CONDITIONS: temps in low 30s, low humidity (lots of interfering streetlights)

12.5" f/5 Discovery Dob
14mm ES 82* eyepiece (113x)

NGC 2022 (Ori)—much larger than IC 418—no central star visible—20-25” across—roundish—OIII filter almost overpowering—shape hard to tell—edges bleed away into surroundings, not sharply-defined at all—maybe an extra 1-2” around inner part—11-12 mag—not one of brightest winter planetaries, but easy to find— brightest star in field maybe 7-8 mag—nebula very diffuse, little smaller w/o filter—brightening to south side—almost like an E-W separation, nebula brighter N-S—7th mag star off to P side of nebula by about 18’

Howard B
October 21st, 2015, 07:52 PM
I have an observation of NGC 2022 from a few years ago with the 28 inch:

"Bright and well defined, 2022 stands out well at 105x and takes magnification well. Slightly oval with an obvious darker center, the best view is without a filter at 408x. However, a faint stellar point is detected within one side of the ring when using the UHC filter! No sign of a central star though - interesting! 21.16 SQM."

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ChristianR
October 22nd, 2015, 05:17 PM
Nice choice Mark, there are not many PNs which can be reached with smaller apertures within this constellation.

Here is my Observation with 12"
1831
NGC2022
Location: Backcountry of Munich
Date: 21. Mach 2012
Local Time: 10pm
SQML = 21,05 mag/arcsec*2, Hum. = 80%, seeing II-III
Dobson: Hofheim Instruments 12" F/5
V = 375x (Nagler Zoom at 4mm)
no filter

Uwe Glahn
October 22nd, 2015, 06:03 PM
I can contribute an observation with 16". I could also not pick up the CS, but like already written the [OIII] knot with UHC filter.

16", 450x, UHC, NELM 6m+
1830

Steve Gottlieb
November 1st, 2015, 02:18 AM
Here are 4 more observations I've made (among others), with 4 different scopes

48" (2/21/12): at 488x, this bright, double-shell planetary contains a bright oval ring oriented SSW-NNE, ~23"x18". The annulus is fairly thin with a relatively large, darker central hole, though the contrast is fairly low. At the exact center is a faint central star (close to 16th mag?). The ring has an irregular surface brightness; slightly brighter at the ends of the major axis, particularly the SW end (knot or star?), and slightly fainter along the minor axis. Surrounding the ring is a fainter and rounder outer shell, ~32" diameter. The outer shell was surprisingly prominent and exhibited a pinkish hue.

24" (1/25/14): at 500x appeared as a fairly bright knotty annulus, slightly elongated SW-NE with fascinating structure. The rim was clearly brighter along an ~200° arc running from the southwest counterclockwise to the northeast. Very small brighter knots were definite at the SW and NE ends and perhaps a slight brightening at the NW edge. In general, though, the rim appeared mottled and sparkling though clearly dimmer along the southeast side, giving a "C" appearance. At 750x, the darker center was also irregular in surface brightness and occasionally, the extremely faint central star sparkled.

18" (2/24/06): at 220x appeared moderately bright, fairly small, round, ~25" diameter, very slightly elongated, irregularly lit and brighter along the western half of the rim giving a "C" appearance. A faint sparkle is occasionally visible on the WSW edge of the rim and images show this may be a faint superimposed star or knot in the planetary. 320x provides an excellent view with the planetary weakly annular and the rim a bit dimmer on the SE side. At 435x, the shape is slightly elongated SW to NE, ~27"x22" with a mottled interior and a brighter rim, particularly along the western half. The appearance is quite patchy at 565x and the sparkle on the SW end is still evident. The central star was not seen at any power. Ced 59 (surrounding FU Orionis) lies 48' due east.

17.5" (2/2/02): immediately picked up at 100x as a very small, bluish-gray "egg" of fairly high surface brightness. Good contrast gain with OIII filter. At 380x (unfiltered), it appeared as fairly bright, clearly elongated SSW-NNE, ~27"x20". The surface brightness was irregular or mottled with a slightly brighter rim and darker center giving a weakly annular appearance. The rim seems to have a couple of slightly brighter spots and the ends of the minor axis are slightly dimmer. No sign of a central star.

Bob Douglas
November 6th, 2015, 04:53 AM
I have an observation with my 28" f/3.6 Starstructure when I was at the star party "Calstar" at Lake San Antonio in California in 2012.
I wrote that using a 7 Nagler (366x) was best--no filter. I got glimpses of the rim star and bright patches on the outer halo. No central star was observed. I will have to look again this winter.