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IC 5070
IC 5070
Pelican Nebula
Emission Nebula in Cygnus
Click here for higher-resolution versions: 40% (1638x1638) 65%
(2662x2662) 100% (4096x4096)
Click on image to cycle through the six versions of the image (described below)
IC 5070 is a large emission nebula, visually located in the constellation Cygnus. The name of this nebula is derived from the appearance of the entire nebula, which
strongly resembles a Pelican (to be more accurate, the "pelican" is only a part of a much larger emission nebula, which includes the North American Nebula; this photo shows the head and some
of the beak of the "pelican" (see link below for a photo of the entire Pelican Nebula). One of the more prominent structures in this photo is
Herbig-Haro Object 555, a very active star-forming region; it is the tube-like structure just above the center of the image,
which looks a bit like an elephant's trunk.
The nebula is predominantly red in the true-color version, because (i) ionized hydrogen emits in the red part of the spectrum; (ii) the dominant emissions captured in this photo are from hydrogen
being ionized (stripped of its electron) by the energetic new stars being formed inside the nebula.
The field is thought to be about 1,800 light years from Earth; at that distance, this bit of the nebula would be about 20 light years across. Visually, this field is about the width of a full moon
(although very dim by comparison).
I had imaged this region 20 years earlier, in the very early days of my imaging work, with a small telescope, from my suburban Seattle yard. I was (and still am) quite pleased with the old image.
To see what a bit of acquired skill, much better location and much better equipment/software
can do, compare this current image to my original one here.
I have presented this object in six different formats; I like each one in its own way. This is the order in which they appear as you cycle through (by repeatedly clicking on the photo, waiting for
each to download; each is labeled in the lower left corner), starting with a reddish version:
(i) A true-color version (the top photo in the stack, labeled "LRGBmix"), with the color created by imaging through red, green and blue filters (with a significant amount
of Ha and OIII data blended into various channels, in varying percentages; Ha emissions are in the red spectrum, and OIII emissions are blue-green, so I have blended Ha into the luminance layer and
the red channel, and OIII into the green and blue channels). This is a blend of the second and third images described below; Steve Cannistra suggested I try it, and I like it better than any of the
other "true color" images.
(ii) A true-color version (the second photo in the stack, labeled "LRGB"), with the color created by imaging through red, green and blue filters only (no Ha or OIII data
included). It is interesting to see how much the addition of the Ha and OIII increases the detail, but it's also interesting to note the more vibrant colors--especially star colors--that often appear
in the RGB version (this is the reason for hybridizing (ii) and (iii)--getting some of the detail from (iii) while keeping the more vibrant colors).
(iii)A true-color version (the third photo in the stack, labeled "LRGBNB"), with the color created by imaging through red, green and blue filters (with a significant
amount of Ha and OIII data blended into various channels, in varying percentages; Ha emissions are in the red spectrum, and OIII emissions are blue-green, so I have blended Ha into the luminance
layer and the red channel, and OIII into the green and blue channels).
(iv) A bi-color version (almost true-color version; the fourth photo in the stack, labeled "HOO"), in which "red" is ionized hydrogen emissions (Ha), and the green and blue
channels both are doubly-ionized oxygen emissions (OIII), which are blue-green in color. It's a fair substitute for having red, green and blue channels, but, because the green and blue channels are
the same, there is a lot of blue-green color in the stars (which I have moderated in processing). It's interesting to me how close this came to the much more complex (with much more data) true-color
version above, but with some less color breadth; people who image from badly light-polluted locations often use this method, since narrow-band light is much less affected by the light pollution.
(v) A version in the Hubble palette (the fifth photo in the stack, labeled "SHO"; lot of the Hubble photos, including and especially the famous "Pillars of Creation,"
are made with this set of filters, since it's a useful set for scientists to see what's actually happening), which shows SII emissions as red, Ha emissions as green, and OIII emissions as blue.
Because Ha emissions so dominate this nebula, I have significantly de-emphasized them in this rendering. With that, the OIII emissions show as pure blue (would be a blue-green otherwise), and
the SII emissions show as a ruddy brown/yellow (would really show up much otherwise). This form of combining results in magenta-colored stars, which I have significantly desaturated.
(vi) A pure Ha version (the sixth photo in the stack, labeled "HA"), showing only emissions from the ionized hydrogen atoms in the nebula.
These are the most frequent ways images of emission nebulae are likely to be presented, so I thought it would be fun to include all of them, to be able to compare and contrast the different presentations:
The "true color" version which includes a little of the Ha and OIII data (the first image in the stack) is, to me, the most beautiful of the lot, so I put it at the top; the narrow-band data
adds contrast, depth and detail to the image, and makes the stars smaller, which is pleasing to me, while maintaining the "true color" nature of the data.
The true color without the Ha and OIII data is pretty, to me, though less dramatic than the image with Ha and OII data. I like the subtle changes of colors (and more vibrant colors) as you scan the image.
The bicolor/HOO version is kind of cool, in that it is fairly true to the "true color" versions, but with a lot less data (images taken only through two filters).
The Hubble palette version is interesting, showing the dominance of the Ha emissions, while also showing that there are significant OIII emissions (the blue) and even some SII emissions
(the yellow/orange pieces), and it's nice to include the (relatively sparse) sulfur emissions that I spent a bunch of hours gathering. This one has yellows (a mix of hydrogen and sulfur emissions) that are
a good deal more vibrant than usual.
And the pure-Ha version is always dramatic, to me, showing as it does so much structure.
Technical Information:
Ha:OIII:SII:L:R:G:B: 570:600:660:672:180:210:260 (a total of over 52 hours of light-frame exposure time); luminance was a blend of 15-minute individual exposures and 3-minute individual exposures;
red and green exposures were all 15-minute exposures; blue all 20-minute exposures; Ha, SII and OIII were all 30-minute exposures. The luminance layer is a blend of the images taken through the luminance filter and the
images taken through the Ha filter. The red channel is a blend of the red-filtered data and the Ha-filtered data. The green channel is a blend of the green-filtered data and the OIII-filtered data. The blue channel is
a blend of the blue-filtered data and the OIII-filtered data.
Equipment: RC Optical Systems 14.5 inch Ritchey-Chrétien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with
internal filter wheel (SBIG filter set), guided by an SBIG AO-X, all riding on a Bisque Paramount ME German Equatorial Mount.
Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X.
Processing: All images calibrated (darks, bias and sky flats), aligned, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization,
color calibration, noise reduction with NoiseXTerminator; deconvolution using BlurXterminator) done in Pixinsight; some cleanup finish work was done in Photoshop CC.
Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.
Date: Images taken on many nights in August and September of 2023. Image posted January 28, 2024.
Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.
Seeing: Variable, but generally good
CCD Chip temperature: -25C
Copyright 2023, 2024 Mark de Regt