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Monday, December 3, 2018

The Giant Cosmic Squid Nebula, Au4, new compositions

I have published my photo of the Giant Squid Nebula. Au4, earlier at November 28. I made a new composition out of the same material, it's little more dynamic now, I think.

I started this imaging project at this autumn season and after a several months I got it ready!
This is a dimmest target I have shot so far! Total exposure time for the light from an ionized oxygen (O-III) alone was around 35h. Most of the data was shot at binned down to 4x4! For some details I shot about ten hours of 2x2 binned data. H-a is brighter but not bright either. There is about ten hours of H-alpha light exposed. There is very little light from an ionized sulfur, I shot bin 4x4 data about three hours for S-II. Total exposure time used is around 48h

The Celestron Edge 11" telescope with a 0.7 focal reducer has a perfect field of view for this object. This combo delivers a very high quality image from edge to edge. The Apogee U16 can be very challenging to have a good orthogonality and collimation due to very large CCD-shell. 

Ou4, the Giant Squid (Giant indeed, it's 50 light years across)
Please, click for a large image

Natural color scheme from the emission of an ionized elements, H-a, S-II and O-III. This is a very large nebula, this image spans vertically about 1.5 degrees = three full Moons side by side in a sky.

Ou4 in light of an ionized oxygen alone, O-III
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This photo shows only the O-III channel. The Squid Nebula is visible only at light of an ionized oxygen, O-III

Wider field of views, Ou4 inside the Sharpless 129
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An older photo of Sharpless 129 is combined with a new data. Image is in natural color palette.
This photo of Sharpless 129 was taken with Tokina AT-X 300mm f2.8 camera optics, QHY9 astrocam and the Baader narrowband filter set, H-alpha, S-II and O-III.

Even wider field of view shows the IC 1396

Note, there is a white circle at lower right corner showing an apparent size of the full moon at same scale. (Moon has an angular diameter of 0,5 degrees.) Ou4 and companions are very large objects!
This is a four panel mosaic image of constellation kepheus, taken with Canon EF 200mm f1.8 camera optics, QHY9 astronomical camera and the Baader narrowband filter set, H-alpha, S-II and O-III.

Ou4, the Giant Squid in mapped colors
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Image is in mapped colours, from the emission of ionized elements, R=Sulphur, G=Hydrogen and B=Oxygen.


The giant Squid Nebula cataloged as Ou4. Nebula was discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula's alluring bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. The true distance and nature of the Squid Nebula have been difficult to determine. Still, a recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. The truly giant Squid Nebula would physically be nearly 50 light-years across.

Technical details

Processing workflow

Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 33 iterations, added at 50% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Celestron Edge HD 1100 @ f10 with 0,7 focal reducer for Edge HD 1100 telescope

10-micron 1000

Cameras and filters
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x 2 and SXV-AOL

Astrodon filters,
5nm H-alpha 3nm S-II and 3nm O-III

Exposure times

H-alpha, 30 x 1200 s, binned 2x2 = 10 h
O-III, 105 x 1200 s, binned 4x4 = 35 h.
S-II, 9 x 1200 s. binned 4x4 = 3 h
Total exposure time, 48h

A single 20 min. calibrated and stretched 4x4 binned O-III exposure 
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4x4 binned O-III frame is divided with a bias corrected master flat and subtracted with a master dark. Even after a heavy stretching, very little can be seen in this single 20 min. 4x4 binned  light frame.

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