Object of the Week, November 1st, 2020 - IC 5148/50

[Paul Alsing]

Object of the Week, November 1st, 2020 - IC 5148/50, PN G002.7-52.4, PK 002-52.1, ESO 344-5… in Grus
R.A.: 21h59m35.1 Dec.: -39°23'08" (2000)
Size: 2’
Magnitude: 11.00 Surface brightness 21.1 Mag/arcsec²
Magnitude of the central star: 16.5

I finally went observing for the first time in a long time for 3 nights during the last new-moon window in mid-October. Both the weather and the pandemic had kept me home for many months. I had no observing program planned, so I just whipped up a couple of observing lists using the Data Power Search Tool in SkyTools. One of these lists was for planetary nebulae, and my wife Debbie and I just cruised from one to the next to the next, having a great time in the local Anza-Borrego Desert, and our telescope that night was our 25” f/5 Obsession classic. In the back of my mind, I was looking for a good candidate for my upcoming OOTW post. I found a good one in IC 5148!

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Since I observe from about +33° latitude, IC 5148/50 rises to about 18° above my southern horizon when it transits, which give me a pretty good look when conditions are good. On this particular night, conditions were more-or-less average, but Deb and I got a pretty good look anyhow. IC 5148 presented itself as an exquisite and nearly perfect and fairly thick ring, looking almost exactly like what they call it in Australia, a “Spare Tyre”. On this night there was not much detail to be seen, but I’m pretty sure that I could glimpse the central star, which leads me to think that perhaps the stated magnitude of 16.5 might be understated. The eastern half looked a little brighter to me, but not by much.

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IC 5150 was discovered by Australian amateur astronomer Walter Gale (from Sydney) in 1894… but was subsequently re-discovered in 1897 by Lewis Swift as IC 1848. There is some confusion here regarding position, with Swift’s position differing by about 30” of arc. In any case, the IC 5148 designation is apparently the most accepted one, even if it was discovered 3 years later. I’ll bet that Steve G. can shed light on this issue and set us all straight.

IC 5148/50 is about 3000 light-years away and is a couple of light-years across. It is expanding at a rate of about 30 miles per second, one of the fastest expansion rates of all planetary nebulae.

This guy was the highlight of our observing that night, and for good reason!

As always, give it a go and let us know.

[Raul Leon]

Hi,here's my observation from 9/22/2017: IC 5148 is a planetary nebula in Grus ; magnitude:11 ; size:2' ; large ; annular with dark central area ;I did not observe the 16.5 mag central star ; left side of ring seemed brighter than right side; OIII filter with my 14.5 Starstructure Dob f/4.3. I used a 17mm Ethos at 93x 4064

[Steve Gottlieb]

What a beautiful planetary! Gale discovered it outside Sydney (in Paddington) in 1894 with an 8.5-inch reflector and mentioned it was just visible in his 6-inch reflector, as well as a 5-inch refractor. Gale obviously owned several telescopes, and stated that in his new 10-inch reflector it spanned 45"x35" N-S, with the central vacancy less than half the diameter and not entirely dark.

Gale announced the discovery in 1895 in the Journal of the British Astronomical Association, but Swift still thought it was new when he found it again in 1897 at Echo Mountain in the San Gabriel mountains (southern California) above Altadena.

I agree the central star is brighter than mag 16.5 -- I've seen it from Australia with an 18-inch. In fact, here's the full observation...

18" (7/6/02): at 171x and UHC filter, this beautiful planetary appears as a large round ring, nearly 2' diameter, with a bright, thick annulus that is irregularly lit. The rim is slightly brighter and thicker along the SE side and also appeared slightly enhanced on the NW side. The central hole appears 25"-30" diameter and is dark except for a central star that was intermittently visible at 228x unfiltered (supposedly magnitude 16.5). Good contrast enhancement with a UHC filter. A mag 10.5 is off the SSW side, 1.8' from the center.

If anyone's interested, here is Gale's discovery announcement (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?journal=JBAA.&year=%3f%3f%3f%3f&volume=...6&letter=.&db_key=AST&page_ind=218&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES) (page 218 and 219)

[akarsh]

I have a log of this object through my 18" f/4.5 on 2015/10/13 from near Pontotoc, TX (~Bortle 2). Below is my rough sketch and notes:
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Looks like I missed the central star :D

[KidOrion]

An old observation from south of Carbondale, IL. I often observed objects as close to the southern horizon as I could, even when they were diminished by the low altitude. I also saw this one in a 70mm TeleVue Pronto from a different site just west of the one in the notes below. Scope was a 12.5" f/5 Discovery Dob.

7/24-25/14
GIANT CITY STATE PARK VISITOR CENTER PARKING LOT
MOON: 27 days, absent
SEEING: 7 (4 at horizon)
TRANSPARENCY: 7 (horizons 6) MW brilliant and rather detailed; temporary cirrus influx
NELM: 6.1
WEATHER CONDITIONS: good; temps in 70s, somewhat humid
many sporadic meteors
With RM

1:57 AM
IC 5148/50 (Gru)—w/UHC (better than OIII?)—found with 24mm SWA—14mm best view—1.75’ diam—to S edge a bright field star touching edge—averted extends to 2’—V. round—suspected annularity; ring thick—V low in sky—to F side is a bit of brightening of ring—w/OIII, biggest brightening is on P side [?!]—no central star with or w/o filter—definitely annular w/averted—ring 0.75’ thick, central opening V. small

[Ciel Extreme]

From home, this planetary scrapes along my southern horizon, but in October 2014 I made a trip down to Marathon Tx where I observed 122 objects over three nights; 121 of them were galaxies and IC5148 was the odd man out. My notes: “Although faint this PN is pretty large and well seen as a well defined disk, quite circular and a little brighter and more strongly defined along the eastern rim. The OIII filter brings out the annularity somewhat; the central region appears a little darker; no central star seen.”

[Bertrand Laville]

Hi All,

Here are two drawings of this beautiful target, seen from Namibian sky, through a T280, C11 Celestron, and a 20" dobson Obsession.
Report here, with a 80 mm added.
http://www.deepsky-drawings.com/ic-51548-t280/dsdlang/fr


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

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[Uwe Glahn]

Not visible from Central Europe I can contribute one result from Namibia.

With 17" and 182x I wrote: very large, bright, nearly circular ring; brighter arcs to the east and west; estern arc with a stellar peak; western arc with spots at its end; CS visible without filter; good and positive reaction to [OIII] filter, but best view without filter

sketch: 17", 182x, without filter, NELM 7m0+
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home (http://www.deepsky-visuell.de/Zeichnungen/IC5148.htm)

[Bill Weir]

From my latitude it culminates right now at < 4° from the theoretical horizon and the Olympic Mountains in Washington State Across the water bite into my horizon from the observatory. I’ll be going out there Saturday night. If I can manage to be setup before 1900hrs I might give it a go to start. I’m always up to a good challenge.

Bill