The Elephant Trunk IC1396A in HOO and with an OSC: color mix variants (Rick Veregin)

The Elephant Trunk IC1396A in HOO and with an OSC: color mix variants

The Elephant Trunk IC1396A is part of a much larger nebulosity and star cluster IC1396 which is more than 100 light years across and about 2500 light-years away. The trunk itself is a dark globule of cold dense gas surrounded by hot ionized gas that has been energized by the very bright massive star HD 206267 to the east (top in my image). The conditions here are ideal for star formation, and indeed there are over 250 young stars that have been identified, some less than 100,000 years old.

This image was taken in with an L-eXtreme Ha/OIII narrow band filter, taken over 14 nights in September, October and November. It was developed in StarTools equally for all channels, with no manipulation of the relative color values.

In Photoshop, the channel mixer was used in different ways. In all cases the OIII from the B channel was ignored, the B was 100% from OIII in the G channel, while the Ha was left in the R channel. The reason for ignoring the B channel is that it has the same information as the G channel (when using a NB OIII filter), but the B channel has only 50% the signal of OIII in the green channel (due to the relatively poor overlap with the B filter, while OIII in the G filter is near the overall peak in the transmission for the camera sensor). Also, there two times more G pixels than B, which helps reduce the noise in the G. This approach is apparently from @Luke Newbould (see Lukomatico on YouTube), though I have not found his discussion of the procedure yet.

Two variants were tried:

In first case the process was as described above except that the G channel was 20% Ha and 80% OIII G channel signal, and the B channel background level was increased for a neutral background. The result retains the HOO look, and the 20% Ha in the G helps with a reasonable match to star colors.

The second case followed the same general procedure, using 60% Ha and 40% OIII for the G channel, which turns the red to a more orange-gold hue. Also, a curves stretch was done on all three channels to better equalize all channel histograms. The result is a sort of SHO look, which I understand was Luke’s intent. Note the stars were treated separately, with the same channel mix in G = 20% Ha = 80% OIII (G), for a natural RGB look.

Personally, I like the color a little better in HOO, but “SHO” provides a bit more contrast. If you have any comments on these approaches, or others for HOO and an OSC camera, I would love to hear them.

Final
Original
B
C
D

B

Description: HOO with no stars

Uploaded: ...

C

Description: HOO as an SHO simulation

Uploaded: ...

D

Description: HOO as SHO simulation, no stars

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	6685169
PixInsight job	Y28F4MJRD5GSFXTOVL532O9ZPDHWYRQ4
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	21h36m02s.34
RA (top/left)	21h39m08s.70
RA (top/right)	21h39m10s.54
RA (bottom/right)	21h32m52s.98
RA (bottom/left)	21h32m56s.92

Dec (center)	+57°29′00″.9
Dec (top/left)	+57°12′10″.9
Dec (top/right)	+57°45′46″.0
Dec (bottom/right)	+57°45′33″.5
Dec (bottom/left)	+57°11′58″.5

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