Object of the Week - January 22nd, 2017 – IC 423/424/426 "The Forgotten Nebulae in Orion"

[Uwe Glahn]

IC 423 (LBN 913, DG 58, “Teardrop Nebula”)
RA: 5h 33,4’
DEC: -00° 38’
Size: ~6’x3’

IC 424 (LBN 914, DG 59)
RA: 5h 33,6’
DEC: -00° 25’
Size: ~2’x1’

IC 426 (LBN 914, DG 59)
RA: 5h 36,5’
DEC: -00° 17’
Size: ~7’x6’

Next to the prominent (M 78, NGC 2024…) and very prominent (M42/43) nebulae in Orion there are some forgotten and often overlooked but very nice objects in the direct neighborhood.

In 1888 Williamina Fleming found three new nebulae on a photographic plate of the 8-inch “Bache refractor” at Harvard College Observatory. They found no entry in the already completed NGC, but in the IC I as IC 423, IC 424 and IC 426.

These reflection nebulae seem to be shaped from stellar winds and a resulting “shock front“ away from the bright star Alnilam. Alnilam, the middle star of the belt of Orion and around 1500ly away could be the illuminating star.

IC 423 and IC 426 could easily be detected with an 8-inch telescope. Bigger apertures gave astonishing details in these nebulae. Beside the interesting shape the three fainter following refection nebulae in the neighborhood of IC 426 could be an interesting and challenging task.

75'x75' DSS blue
2455


sketch IC 423:
27", 172x, NELM 6m5+
2456


sketch IC 426:
27", 172x, NELM 6m5+
2457

As always, give it a go and let us know

[Daniel_Sp]

Hi Uwe,
really hot objects... I've already seen your sketches on your homepage, since I check your site pretty often to get inspired for my own upcoming observations.
I'm not sure if I might see them under my local conditions, even with 24"... The nights thursday/friday and friday/saturday shall be clear in the far western germany. So I'll give it a try.

Viele Grüße + CS
Daniel

PS: viele Grüße = best regards :)

[Howard B]

Hi Uwe, I agree with Daniel - these look like great objects! I've never given them a try but now they're at the top of my observing list.

[Robin]

Hi Uwe,

That's an interesting selection of nebulae! Actually, I've never been aware of their existance at all...
Last night I gave it a try with my 12-inch Dobsonian.



IC 423
With 47x magnification I couldn't see the nebula at all. Then I experimented with different eyepieces and figured out that the view was best at 84x magnification. Seems to depend a lot on exit pupil. I saw a small and diffuse cloud that was only slightly brighter that the sky background.


IC 424
I couldn't see this nebula at all.



IC 426
This nebula was larger than IC 423 and I could see more structures. At 84x magnification I saw a crescent-shaped nebula around a triangle of 11-12 mag stars with a small appendage at its Northern part and a bulge opposite to this triangle.


DG 62
Questionable sighting. At some times I thought I could see a litte elongated patch at 168x magnification.
If there are any other sightings of this nebula with 12" aperture, I'd be more confident. Otherwise, I'll probably conclude that I didn't see this object.
Anyway, I'm curious about the smallest aperture that could pick up this nebula.


DG 63, [OS98] 37
I couldn't see these nebulae at all.


Please find attached my sketches.



By the way, which catalogs do the abbreviations DG and [OS98] stand for?



Clear skies

Robin

[Jim Chandler]

We took a look at these last night in the 30", as the transparency was excellent, using 226x. IC 424 is best described as "subtle"; just a faint background glow around the stars. IC 426 was the favorite, with that intriguing plume coming off to the southeast. Topknot of an exotic bird or perhaps a whale spouting? The kidney bean shape of IC 423 with the bright-rimmed horseshoe shaped lobe extending to the south was impressive.

While we were in the area, we revisited the NGC 1973/1975/1977 nebula complex, then dropped southeast to Sh 2-308, which usually is frustratingly dim. Last night it showed surprisingly well at 94x using an O-III filter. I was able to trace the edge of the bubble around a full semicircle, and the brightest portion showed filamentary detail similar to the Veil.

[Uwe Glahn]

Nice, some observation come along. I must confess that the beauty started with bigger aperture like Jim wrote but the pure visibility started much smaller. The exciting point is, that there are some overlooked RN in this well known region in the sky.


By the way, which catalogs do the abbreviations DG and [OS98] stand for?
- DG stands for "Dorschner + Gürtler" - two German astronomers (concerning paper: 1963AN....287..257D)
- [OS98] stands for a paper from "Ogura + Sugitani" in 1998 (concerning paper: 1998PASA...15...91O)

[Robin]

Hi Uwe,

Thank you for the paper references. I guess observing all the possible nebulae from those lists must be an interesting observing project for large apertures, if someone has enough time to do it!

Clear skies

Robin

[wvreeven]

My observations of Saturday night (25 Feb) from SQM 21.4 skies with excellent seeing:

IC 423: At 83x and 151x visible as an elongated patch of light. Best at 83x because it is compacter then though at 151x I see it to be hamburger shaped. Two bright edges with a darker lane in between them. I cannot make out the horse shoe shape.

IC 424: At 83x and 151x visible as an oval patch of light with two faint stars in it. Best at 151x.

IC 426: At 83x and 151x triangular. Best at 151x. The nebula looks triangular with one side running along a string of stars from west to north east and another side due east. At the east another faint patch runs south but this is very hard to see. East of that lies another elongated patch running more or less nort south (DG 62) and even further east another small oval path (DG 63). I am not sure if I saw a third patch ([OS98]37) running away from a bright star between IC 426 and the first patch to the east. I suspect the bright star to be a bit nebulous but I am not sure.


Clear skies, Wouter