IC 405: The Flaming Star Nebula...

IC 405: The Flaming Star Nebula

Object: IC 405 (Caldwell 31, Sharpless 2-229)
Type: Emission and Reflection Nebula 
Constellation: Auriga
Distance: 1500 light years

Dates: 4th. and 9th. December 2019
Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 20 x Red (300s), 20 x Green (300s), 20 x Blue (450s), 40 x 300s H-alpha: no flats/darks (hot pixel removal in Astroart).

IC 405 can be found in the constellation Auriga, high in the Orion Milky way in the south-eastern sky during early winter. It was discovered in 1892 by J.M. Schaeberie, M. Wolf and E. von Gothard on photographic plates while investigating Nova Aurigae 1891.

Stellarium map showing location of IC 405

IC 405 appears as a full-moon-sized glow surrounding the variable star AE Aurigae. It is extremely difficult to see visually from suburban skies with amateur telescopes.

It is located adjacent in the sky to another nebula, IC410, although the connection is merely a line-of-sight effect as IC 410 is a much more distant object.

The variable star AE Aurigae (indicated on the hydrogen alpha image below) is thought to be the source of the energy which illuminates the nebula, whose light is a mixture of fluorescence from ionised gasses (red) and reflected starlight from surrounding dust (blue).

Measurement of the star’s velocity suggests that it was not formed from this material.  Instead, AE Aurigae is believed to have originated in the vicinity of the Trapezium star-forming complex in Orion.  The star is thought to have once been part of a binary star system with a massive companion that went supernova, and whose expiry released it from its gravitational anchor, catapulting it from its birthplace around 2.5 million years ago.

Hydrogen alpha image of IC 405, with AE Aurigae indicated...

Its current velocity of approximately 35 miles per second will carry it through the five light year-wide cloud of gas and dust that forms IC 405 within the next 20,000 years, which will cease to shine once its illuminating star exits the region.

The Ha frames were gathered in the presence of an 80% gibbous moon located just 30° from the target. The RGB frames had been collected earlier without the bleaching effect of a bright moon.  Processing technique is described here.

Some 10 years ago I previously imaged this area with a 135mm camera lens to capture both IC405 and IC 410, and although the image is a low resolution one it does give an indication of their adjacency in the sky.

Sharpless 2-142: The "Wizard" Nebula...

Sh2-142: The "Wizard" Nebula...

Object: Sharpless 2-142 (Sh2-142), with open cluster NGC 7380
Type: Emission Nebula and open cluster
Constellation: Cepheus
Distance: 9700 light years

Dates: 29th November, 2nd and 3rd December 2019
Equipment: ATIK 460EX with EFW2, Skywatcher f5.5 Esprit 100 ED refractor, Avalon Linear mount, guiding with Lodestar X2/PHD

Subframes: 16 x 600s H-alpha, 16 x 600s SII, 16 x 600s OIII, no flats/darks (hot pixel removal in Astroart).

Sharpless 142 is a diffuse emission nebula surrounding the developing open star cluster NGC 7380. NGC 7380 was discovered by Caroline Herschel in 1787. William Herschel included his sister's discovery in his catalogue, and labelled it H VIII.77. The nebula itself is very faint and eluded the eagle-eyed Herschels.

Stellarium map showing location of Sh2-142

It can be found in the constellation of Cepheus, which is virtually overhead during autumn evenings in the UK. The nebula occupies an area approximately equal to that of the full moon, but is very difficult to see visually with telescopes, especially from suburban locations

The nebula spans about 140 × 75 light-years in space and lies within our Milky Way Galaxy.

 

The Sharpless designation comes from the Sharpless catalogue of 312 emission nebulae (H II regions). The first edition was published by Stewart Sharpless in 1953 with 142 objects (Sh1) and the second and final version was published in 1959 with 312 objects (Sh2).

The cluster and nebula are part of an even larger and optically invisible molecular cloud designated NGC 7380E, estimated to contain 6000-15000 solar masses of dust and gas.  It is believed that the star formation that created the stars of NGC 7380 began some 4 million years ago and continued for another 2 million years before it largely ceased, with radiation from the stars dispersing the cloud from which they formed and ionising the remaining gas to produce the emission nebula we see today.

Mist and freezing condensation terminated all three imaging sessions before midnight. Auto-guiding was also a pig, with an RMS of anywhere between 0.7 to 1.2, giving rise to rather poor resolution and bloated stars. I'm not sure whether that's down to the mount (balance seems absolutely critical) or poor seeing. The seeing certainly wasn't good for any of these sessions: I could see the focus star rippling violently whilst trying to get a sharp focus, which in the end just turned out to be a best guess. 

The Ha, SII and OIII frames were stacked in Astroart and then RGB combined in PaintShop Pro. A blend of 50: 50 SII/Ha was used for the red channel, 30:70 Ha/OIII for the green and 100% OIII for the blue, with further curve changes, star reduction and denoising in PSP to give the final image. This was the first time I had tried adding some SII data into the mix, and it certainly seems to add some contrast to the final image.

The colloquial name of “the Wizard” alludes to an apparent figure in a pointy hat that can supposedly be made out in the nebulosity but like so many of these more recent monikers, I’m not sure I can see it myself.  Maybe it looks more like Roy Wood....