The Tarantula Nebula - it's not easy being green (Niall MacNeill)

The Tarantula Nebula - it's not easy being green

Each year I come back to this one. It is such an iconic object, nestled in the Large Magellanic Cloud and we in the Southern Hemisphere are so lucky to have access to it.

This is an LRGB (colour) image. The Ha narrowband is shown in Revision B and can be accessed via the mouseover.

When I first imaged this obect 7 years back with a DSLR (see Revision C).....not great I know, but I was just learning this craft!, it showed up as being quite blue/ green. I didn't know it then but clearly there is a lot of OIII emission going on there. Of course, the DSLR's IR filter wiped out most the red Ha emission. However, most of the images we see today have that green suppressed or even largely absent. In fact I was told once that it is a red object and not a lot of green shows up in a "proper" astroimage. Well, here I am 7 years later, with a decent CCD camera and nice filters, having colour calibrated the image in PixInsight with Spectrophotometric Color Calibration and there is a still a lot of green there. Many, including myself, have used the Ha signal to enhance the red signal. Whilst the result can be quite nice, it almost inevitably blows away the green and where the Ha and OIII overlap, the colour becomes a washed out white. To avoid that there is a lot of messing around with masks etc. The Ha image by itself shows tremendous detail, but I think its truest rendition is as a monochrome image. The AstroBin mouseover is a great way of showing the Ha against the colour image and it is interesting to see where the Ha is in the colour image.

And so here is The Tarantula Nebula, in colour, preserving the teal colour coming from the OIII emission, intermingled with the red, coming mostly from the Ha emission line.

Final
Original
B
C

B

Description: Ha

Uploaded: ...

C

Description: A DSLR image from 2016

Uploaded: ...

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Status	Advanced success
Started	...
PixInsight job	O94MJ0OHOIOPTERHX8QJNTHTK38WRPUO
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	05h38m48s.775
RA (top/left)	05h35m13s.749
RA (top/right)	05h35m11s.988
RA (bottom/right)	05h42m29s.519
RA (bottom/left)	05h42m18s.371

Dec (center)	-69°09′56″.64
Dec (top/left)	-68°49′38″.74
Dec (top/right)	-69°30′18″.67
Dec (bottom/right)	-69°29′53″.71
Dec (bottom/left)	-68°49′16″.62

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