Object of the Week, March 6, 2022 – NGC 2736 = Pencil Nebula = Herschel's Ray = ESO 260-N14 = RCW 37

[Paul Alsing]

Object of the Week, March 6, 2022 – NGC 2736 = Pencil Nebula = Herschel's Ray = ESO 260-N14 = RCW 37 in VELA

R.A.: 09h00m24.0s
Dec.: -45°54'00"
Size: 30'x7'; Magnitude: 12.0?

NGC 2736 is pretty low for most of us northern hemisphere observers… but at least it is 2° higher than Omega Centauri…:D On a decent night, I can get pretty good views from my local desert observing location near San Diego, California, when the Pencil Nebula culminates at about 13° above my southern horizon.

The emission nebula NGC 2736 is the brightest part of the 11,000-year-old Vela Supernova Remnant (https://en.wikipedia.org/wiki/Vela_Supernova_Remnant), which is one of the largest and brightest features in the X-ray sky, being about 8° across… about the same size as the constellation Crux!

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The Hubble can’t fit the whole 30’ length thing in…

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Of course, one of the APOD photos of NGC 2736 is over-the-top… and one isn't...

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On 1 March 1835, John Herschel discovered this object on March 1st, 1835 at the Cape of Good Hope and described it as "eeF, L, vvmE; an extraordinary long narrow ray of excessively feeble light; position 19 ±. At least 20' long, extending much beyond the limits of the field..."

The length of the Pencil Nebula is about the same as the diameter of the full moon, so a low-power eyepiece is the way to start when observing it. A 31mm Nagler with an NPB filter in my 25” f/5 Obsession Classic yields about a 45’ FOV and is a good starting point for me. It was easily picked up as a long and ghostly streak, slightly warped at each end. Increasing the power shows that there is some vague structure to be teased out and some variability in brightness along the length, with the northern portion being brighter than the southern, which just seems to fade away into nothingness.

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

[Raul Leon]

Hi, here's my observation from 2/20/2020: ngc 2736 is a nebula in Vela; magnitude 12 ; size:30' x 7' ; aka Herschel's ray after it's discoverer, it's an extraordinary long ,narrow ray of light, not very high in my sky, on a night of good transparency and superb seeing I caught a good glimpse of this elusive target. For many years I tried but could not see it very well because of it's low location , clouds, etc. I used my DGM filter this time out and there it was! I used a 21mm Ethos at 115x with my 14.5 Starstructure f/4.3 and DGM filter4631

[wvreeven]

I observed this nebula from my very light polluted backyard in La Serena, Chile, last year with my 12" dob. My notes read:

At 43x with UHC seen as a very faint, straight and thin glow. OIII gives the best view but still barely visible. H-Beta kills the nebula.

[Steve Gottlieb]

Hard to believe this hasn’t been an OOTW before as it’s such a cool object.

One of several observations:

13.1" (2/18/04 - Costa Rica): Herschel's Ray was easily picked up at 105x using a UHC filter. It extended well over 1/2 of the 38' field, at least 20'x2', oriented SSW-NNE. This prominent Vela Supernova filament is brightest towards the NNE end near a mag 8.3 star which is just following the NNE edge. It appears like a thin splinter of light through the field with a weak filamentary structure and variations in brightness, similar to one of the fainter filaments in the Veil nebula. Several stars are very close to the edge including a mag 11 star near the middle. I was impressed the appearance was very comparable to the view I had through an 18-inch in Australia.

[Uwe Glahn]

Fascinating field Paul.

While the "Pencil" was an easy catch, I suspected some structure with the smaller 12-inch within. These structure was nicely visible in the larger 28-inch on the Gamsberg during Bortle 1 skies.

sketch: 12", 63x, [OIII], NELM 7m0+
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home (http://www.deepsky-visuell.de/Zeichnungen/NGC2736.htm)

[akarsh]

Finally got to look at the Pencil from humid but dark skies at a star party in Coorg in South India (13°N latitude). The conditions were around Bortle 3, with M33 visible to naked eye as an elongated patch, I was using a GSO 16" Dob and a 1.25" Orion Ultrablock filter. The extinction in south India can generally be high because of high humidity, which can make the views mushy and dim especially at low altitudes, but I did not have luck so far catching the Pencil from the USA so I decided to deal with this.

17.5mm Baader Morpheus (104x):
A very weak (although not as bad as Sh2-91, but waaaay fainter than Veil) filament amorphously extends roughly N-S in the eyepiece. The brightest part of the filament that is consistently detected lies around 09h 00m 17s -45° 56' 53" J2000. The full filament could not be discerned and concrete details were difficult to infer.

25mm Super Plössl (73x):
Much better view. More of the filament can be seen, and its elongation can be also detected as being towards the double star to its NE. The brightest part remains to be the aforementioned region, but the extensions on either side appear vaguely whereas the brighter part is more concrete at this lower power.

Clear Skies
Akarsh