Fighting Dragons of Ara

[timc]

Attached is a narrowband image of the emission nebula NGC 6188 – the ‘Fighting Dragons of Ara’ in the southern constellation of Ara.  The nebula lies approximately 4,000 light years from us and the open cluster NGC 6193 is responsible for a region of reflection nebulosity within NGC 6188.  The nebula is a star forming region and is sculpted by the massive, young stars that have recently formed there, some being only a few million years old.  The setup was widefield, capturing a full 3 degrees of sky, although the final image has been cropped slightly.

 

I used a remote robotic telescope in Siding Spring Observatory, Australia, operated by itelescope.net on 28 April, 7 May and 12 June 2020 to capture the data for the image.  The image consists of the following exposures: Ha 300s x 19 unbinned, OIII 600s x 18 binnedx2 and SII 600s x19 binned x2, giving a total of 7 hours and 55 minutes imaging time. The telescope I used was a Televue NP 127mm Apo refractor at f/5.3 mounted on a 10 Micron 2000 HPS mount with a FLI Proline 16803 CCD camera.  I processed the downloaded calibrated sub-exposures in CCD Stack2 with further processing in Photoshop CS5 using the Hubble palette (ie Ha channel mapped to green, SII to Red and OIII to blue). Thanks for looking.

 

[JR]

That's a stunningly great image Tim.  There's so much crisp detail.  I don't know how the colours map to the narrowband sources but the effect is as art like as it is physics or chemistry.  It could be a storm by J M W Turner.  Once again the Universe amazes.

Very well done

James

Sent from my iPad

On 13 Dec 2020, at 20:50, timc <tcos...@gmail.com> wrote:



Attached is a narrowband image of the emission nebula NGC 6188 – the ‘Fighting Dragons of Ara’ in the southern constellation of Ara.  The nebula lies approximately 4,000 light years from us and the open cluster NGC 6193 is responsible for a region of reflection nebulosity within NGC 6188.  The nebula is a star forming region and is sculpted by the massive, young stars that have recently formed there, some being only a few million years old.  The setup was widefield, capturing a full 3 degrees of sky, although the final image has been cropped slightly.

 

I used a remote robotic telescope in Siding Spring Observatory, Australia, operated by itelescope.net on 28 April, 7 May and 12 June 2020 to capture the data for the image.  The image consists of the following exposures: Ha 300s x 19 unbinned, OIII 600s x 18 binnedx2 and SII 600s x19 binned x2, giving a total of 7 hours and 55 minutes imaging time. The telescope I used was a Televue NP 127mm Apo refractor at f/5.3 mounted on a 10 Micron 2000 HPS mount with a FLI Proline 16803 CCD camera.  I processed the downloaded calibrated sub-exposures in CCD Stack2 with further processing in Photoshop CS5 using the Hubble palette (ie Ha channel mapped to green, SII to Red and OIII to blue). Thanks for looking.

 

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<NGC6188 Fighting Dragons of Ara NB T9 December 2020.jpg>

[tcos...@gmail.com]

Thank you for your kind comments James - they are much appreciated. NGC 6188 is a terrific target for narrowband imaging and having seen a few images posted on another astro-imaging forum, I thought I’d have a go at imaging it. The sheer size and scale of this area is breath-taking - roughly 5 or 6 full Moon diameters and the wealth of detail and colour captured by the imaging setup surprised me. It’s been a pleasure to process and I hope others enjoy it too.

Kind regards

Tim C

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[Trev S]

Tim, That is an incredible image.  Using remote telescopes for southern objects makes complete sense for us northern hemisphere dwellers. There seems to be a lot of data in all three bands that you imaged. I assume the skies were exceedingly clear in Siding Spring?

Out of interest, do you have an idea of the approximate cost of nearly 8 hours of imaging time with iTelescope.net?

[William Bottaci]

Hello Tim, excellent image, and taken with just a 5-inch (127 mm). I
do like the wider angle views, when the region of interest is large;
there is of course finer detail in there but other telescopes can take
care of them, and there's plenty of detail here.
Dark skies, top quality telescope, Hubble palette filters and your
processing, incredible what can be done.

A few questions if I may...
- Do you know the band range of the filters, as in nanometres - broad
or narrow band? You mention narrowband but just wondering if you're
using that expression as a general term...

- It's a good quality mount and they're bound to have it well
aligned, but is any guiding involved? If so what involvement is
required by you?

- It'll be interesting to know why you don’t bin the Ha (or why you
bin the others). For extra information: the focal length is 670 mm and
the camera pixel size is 9 μm.
From a quick measurement I get an estimate that a typical star in this
image spans 2 to 3 pixels, given that you've cropped a little. If the
seeing was steady then that's optimal sampling.

Many thanks for sharing.
William

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I hope the following explains a few things, as background information
and for those unfamiliar to this extent:

It's not a straightforward case of putting any camera on any
telescope, unless the object is bright and has very small detail - the
Sun, Moon and planets are good examples. For stars, galaxies and
nebulae there is an optimised match between length of telescope and
pixel size of camera, called sampling.

Sampling: the image of the star should cover a few pixels on the
camera, no more or less (of course with different brightness of stars
- good luck on that one). Go for the faintest, as there are more of
them, and the brighter ones are going to be bloated anyway.

There are several online calculators to tell you an optimised setup
regarding sampling of stars, but in terms of control from the imagers'
point of view, the focal length would be choice of telescope and/or
reducer, but more conveniently: binning of the cameras sensor.

Binning: several pixels can be combined, to make a larger one. You end
up with less definition, but clearly more sensitivity. If the object
of interest in your image is one where definition is not so important
e.g. nebulae, then there's little to lose, and you do need the extra
light.
Long focal lengths and/or small pixels leads to over-sampling of
stars, so binning is appropriate in this case, and as that combination
of equipment produces fainter images the extra light from the sensor's
point of view is beneficial. If the atmospheric seeing is poor, a
point from the object is likely to be smeared out over many pixels
anyway, so that needs to be taken into account.
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