IC 410 and IC 405: Tadpoles and the Flaming Star...

IC 410 and IC 405...

Object(s): IC 410 and IC 405
Type: Emission nebulae
Constellation: Auriga
Distance: 12,000 light years (IC 410) and 1500 light years (IC 405)
Equipment: Atik 460/EFW 2, Samyang 135mm lens@ F2, Vixen GPDX mount, guiding with Lodestar X2/PHD
Date: January 21st. 2023
Subframes: 18 x 300s each for Ha (1x1 binned) and OIII (2x2 binned), 12 x 200s (2x2 binned) for RGB: flats, bias as dark frames.

Location of the field of view in the night sky...

This particular area of the Orion Milky Way, beneath the constellation of Auriga, offers a rich zone of targets for any astrophotographer.  It is an area that I have visited several times before, but the 5 degree field of the Samyang f2 lens offers a chance to place many targets in the same field of view, to show their proximity to each other.

At the top left of the field of view lie the two open clusters, M38 and NGC 1907. I imaged these back in 2010: these clusters lie at around 4500 light years away, in between IC 410 and IC 405. 

Below these clusters lie "The Spider and the Fly", IC 417 and NGC 1931. I imaged these nearly three years ago . 

Discovered by Max Wolf on September 25th 1892, IC 417 ("the Spider") is a star cluster with an associated emission nebula, and lies about 7500 light years away. A wider area of hydrogen alpha emission extends from it and is classified as Sharpless 2-234. The smaller but brighter NGC 1931 was discovered by William Herschel on February 4th 1793, and is also an emission nebula with an associated cluster, as well as an element of reflection nebula. It, too, has a Sharpless designation (Sh2-237) and lies at a similar distance to IC 417.

Designations of the objects in the image field of view...

IC 410 is very much a background object, lying over 12,000 light years away. It is often called the "Tadpoles" nebula, after the two blobs of star-forming dust and gas within it, designated as Simeis 129 and 130 respectively, and which just about show up on the main wide field image above. I pictured these back in January 2019. The nebula IC 410 was discovered by Max Wolf on September 25th. 1892, and strictly speaking the IC 410 designation refers to the brightest area of nebulosity surrounding open cluster NGC 1983, an earlier John Herschel discovery from January 22nd 1827. These days, IC 410 is taken to be the entire nebula, which also has the Sharpless designation Sh2-236.

IC 405 (also designated Caldwell 31 by Sir Patrick Moore in his own catalogue of deep sky objects) is the "Flaming Star" nebula, which I pictured back in December 2019.  It was discovered on March 21st. 1892 by John Schaeberle. IC 405 also has a wider area of H-alpha nebulosity associated with it, designated as Sh2-229, although they all tend to be regarded as "IC 405" these days. At a mere 1,500 light year distant, it is a foreground object compared to the others in this field of view.

The whole area is designated as Sharpless 2-230.  I did take a wide field image of Sh2-230 back in January 2009, but since then both my equipment, software and processing techniques have improved (though the mount is still the same!)

In terms of processing, the biggest problem is that the nebulae are overwhelmed by a blizzard of the Milky Way stars. The magic of the "Starnet" software was used to "de-star" the various narrowband and colour image stacks, allowing me to replace just the brighter stars and clusters back into the image at a more visually aesthetic level.

IC 410: The "Tadpoles" Nebula...

IC 410 and NGC 1893... 

Object: IC 410 (nebula), with NGC 1893 (star cluster)
Type: Emission nebula with open cluster
Constellation: Auriga
Distance: 12000 light years

Date: January 29th. 2019
Equipment: ATIK 460EX, Vixen 114mm f5.3 ED114 refractor, NEQ6 mount, guiding with Lodestar X2/PHD

Subframes: 16 x 600s H-alpha, 10 x 600s OIII, 6 x 150s each for RGB (2x2 binned), no flats, hot pixel removal in Astroart (no main frame darks).

IC 410 is an emission nebula partly obscured by dark, dense molecular clouds, and forms part of a larger star forming region that also contains the Flaming Star Nebula (IC 405, which lies approximately 1.5 degrees to the west of IC 410).  The cluster within, NGC 1893, was discovered in 1827 by John Herschel, but the surrounding nebula IC 410 was not detected until 1892, by German astronomer and astrophotographer Max Wolf.

The nebula occupies an area in the sky approximately 40 arc-minutes in diameter (a bit larger than the full moon). In reality, the nebula is approximately 100 light years across. Visually,I was once lucky enough to just about make out the brightest areas of IC 410 in an 9.25-inch SCT on a night of excellent transparency from a suburban sky. The cluster NGC 1893 appeared to be enmeshed in a faint haze of nebulosity, with fainter lobes to the west and south of the cluster that required a low power (40mm) eyepiece and an OIII filter to provide the necessary contrast. It is not surprising that John Herschel missed it visually.  

IC410 is illuminated by fluorescence caused by the excitation of its gaseous atoms by radiation from the hot stars of the open star cluster (NGC1893) that lies in the centre of the nebula that gave birth to it.  This star cluster is about 4 million years old, but in astronomical terms it is still very young. 

The "tadpoles" of IC 410 (detail from main image)

At the top-left of the star cluster in the image, two columns of dust and gas left over from the formation of the star cluster can be seen.  These objects are designated as Simeis 130 – the lower of the two – and Simeis 129 (the rather obscure Simeis catalogue of nebulae arises from the Crimean Astrophysical Observatory, which has a facility in the town of Simeis in the Ukraine) and are popularly referred to as “the tadpoles”. These structures are thought to contain embryonic stars hidden in the dust and gas that enshrouds them.  As can be seen in the image, the heads of the “tadpoles” are outlined by bright ridges of ionised gas, while their tails trail away from the cluster's central region, evidence of the stellar winds and intense radiation pressure from the stars of NGC 1893.

IC 410 can be found high in the Orion Milky Way in the constellation Auriga, as indicated in the Stellarium sky chart below:

The striking green/blue colour visible in the main image arises from the fluorescence of triply-ionised oxygen atoms (OIII) which seems to be unusually strong in this particular nebula (the orange/red is from ionised hydrogen – Hydrogen alpha emission – which is the principle light given off by most emission nebulae).

Atmospheric stability and clarity were rather poor when I acquired data for the image, but this was the first clear spell that I had been able to make use of in the last six weeks, so beggars can’t be choosers.  The guiding wasn’t brilliant (about 1.2 arc-seconds RMS) and the resultant sub-frames were also very “noisy” due to a high haze of moisture that cut my gathering of OIII subframes short.

Fortunately, the signal was pretty strong in both Ha and OIII and the image stacks, although few in number, did not require much of a stretch.  

The narrowband colour data was RGB combined in Astroart (red = Ha, green =70/30 OIII/Ha, blue = OIII).  The RGB frames were also RGB combined and the result blended with the narrowband stack in PSP to give star colours.