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PostPosted: Wed May 23, 2012 8:15 pm 
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Hi folks,

Globular clusters have always seemed romantic objects to me. As many will remember at one point not too many years ago they were even embroiled in a controversy as it seemed that they were older than the best estimate, using other criteria, of the age of the Universe, a paradox which was resolved after the age of the Universe was more accurately calculated.

The Hercules Globular Cluster is well placed at the moment so I took the opportunity to grab 5 x 200 second subs at each of red, green and blue (Astrodon Tru-Balance filters) while waiting for NGC 7000 to rise. I wasn't expecting too much because even M13 is quite small on my camera's sensor at the prime focus of my TEC 140. Here's the full frame resized to a more forum friendly 1024 x 1024 pixels but you can click the image for a full sized version:

    Image
    M13 - The Hercules Globular Cluster

I rather like this rendition precisely because it does cover such a wide field of view (about 2°) and so serves to emphasise what a jewel M13 is. M13 is described in detail in the Wiki entry here. With due apologies to experienced egg-sucking Grannies the headline features are: 145 light-years in diameter, it is composed of several hundred thousand stars and is about 25,100 light-years away from Earth.

For the extreme pixel peepers here's a central crop at 100%:

    Image
    M13 - The Hercules Globular Cluster

Not as good as this Hubble Space Telescope image, of course!

As globular clusters formed so early in the history of the universe they are poor in elements heavier than hydrogen and helium but it's nice to think that just maybe one or two stars with planetary systems might have got captured as M13 orbits the galaxy. What a spectacular place to live - or visit! 8)

Bob.

Processing notes, executive summary: The 5 x 200 second R, G and B subs were all combined to produce a luminance image. That was combined with the separate R, G and B stacks to produce a colour version to be added back to the luminance version later. Those two images were then stretched and exported from PixInsight to Photoshop as 16 bit TIFFs. Photoshop's Shadows/Highlights tool was used to tweak the brightness near the centre of M13 and then the Topaz Labs InFocus tool was used to increase the micro-contrast. It's the second time I've used this tool on an astro image and it really does a fantastic job provided one takes care not to abuse it. A spot of noise reduction was applied and then the colour image was added as a "Color" layer. A vibrance clipping layer was applied to the colour layer and a few more cosmetic tweaks were applied.

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PostPosted: Thu May 24, 2012 12:38 pm 
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Hi folks,

Sleep deprivation is very much with me after three 4 am finishes on the trot but I couldn't resist trying to find out whether the micro-contrast adjustment in Topaz Labs' InFocus Photoshop plug-in was creating false detail or not. My first issue was trying to match some features as the Hubble image is only about 2.5 arcminutes across. I got there in the end and by dint of downsizing the whole Hubble image and upsizing a 95 pixel square tiny crop from the centre of my own image and applying a very extreme curve I got this result:

    Image

Very rough and ready manual image registration - I'll leave you to work out which image is from Hubble! :lol:

But I do take comfort from the fact that there is a reasonable correlation (might have been slightly better if I wasn't so knackered that I took my crop from the published JPEG rather than the original Photoshop PSD). On this evidence that InFocus is not inventing (a lot of) false detail that plug-in, together with their DeNoise plug-in which I find indispensable, is very definitely a permanent part of my image processing tool-kit from now on. 8)

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
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PostPosted: Thu May 24, 2012 1:18 pm 
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Great job on your pictures, that's really amazing.

One note about the Hubble: the original WFPC2 had 4 CCD sensors of 800x800 each, giving 1600x1600 images, or 2.56 megapixels.

The ACS installed in 2002 has two CCD sensors of 2048 x 4096 each, so it gives 16 megapixel images.

The WFC3 installed in 2009 has two CCD sensors of 2048 x 4096 each, for 16 megapixels, and an IR sensor of 1024 x 1024 for incredible 1 megapixel images.

The largest advantages that Hubble has over even a T2i is the lens itself, and the fact that it is outside the atmosphere (which can refract light).

That being said, if you used a longer focal length, and did a panorama, you could probably achieve very similar results (at least in the visible field ranges).

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PostPosted: Wed May 30, 2012 9:30 am 
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Hi Bob,
That's a nice one!
This object is one that I visit every time I'm out there in the field. I think that I distinguish the "propellor" too in the cropped frame. I hope that I'll soon have one too curtesy my new Orion-UK 10" reflector. This one and Omega Centauri, that is quite low at my latitude, but doable.

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PostPosted: Wed May 30, 2012 10:08 am 
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Bob, that looks absolutely sublime! Well done!

Comparing it to the Hubble shot just makes it more impressive if you ask me! =)

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PostPosted: Wed May 30, 2012 10:23 am 
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@Radu: Congratulations on the new 'scope. I hadn't even heard of the "propellor" until after I processed the image but I wouldn't have processed any differently. Asterisms are fun but an anthropomorphic world view is a bad world view, rather like the inverted logic (IMHO) which allows the anthropic principle to gain credence! Phew, did I just write that? :lol:

@Lorride: Thank you, Ma'am. That Hubble image is misleading, though, as the whole image takes up just the tiniest fraction of the smallest part of the center of my own. :oops: But they do have a bigger budget. :lol:

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Wed May 30, 2012 10:30 am 
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Ma'am? First time I have been mistaken for being female on the Internets :p

How many extra mm in focal length can you extend to optically though? Without losing too much detail nor light.

Tiny difference in budget, you're skills seems to fill out the gap though ;)

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PostPosted: Wed May 30, 2012 11:03 am 
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Hi Lorride,

Whoops, sorry. I've been running on empty so far as sleep is concerned for well over a week with a succession of imaging sessions extending right through to dawn. :oops: At least the combination of a full Moon and cloud will allow me to catch up over the next couple of weeks!

I could probably see slightly better detail with smaller pixels or a 2x corrector but, from what I read on the Net, my 140mm aperture isn't enough to resolve the core even with the best of seeing. That said, I really do prefer the wide view. Maybe my fatigued brain is stalled but to me M13 has an almost 3D look with the tight central core of stars surrounded by the outliers, almost like a swarm of bees around a honey-pot. Good grief, I do need sleep after writing stuff like that!!! :shock:

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Wed May 30, 2012 11:25 am 
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No worries ;)

I see, nothing wrong with wide field, gives an amazing overview!

Sleep tight! =)

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PostPosted: Thu May 31, 2012 10:13 am 
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Hi Bob, thanks. I cannot wait to put the scope to work, I have high hopes for it although many think that a 10" is a tad too heavy( about 12 kg) for the NEQ 6 . I've seen 12" reflectors mounted on it and I hope that it won't struggle too hard. I still have no guiding solution, I hope to get by using shorter exposures, we'll see.
And about anthropomorphic asterisms, well, you have a point, but I cannot call that apparent feature by the name used by the dolphins, because, although they can thank us for all the fish, they didn't divulge us their name for the propellor.:-). I'm not quite happy with inverted logic either, although I should be used to it by now, being exposed to political speeches for so may years :-)

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PostPosted: Sat Dec 08, 2012 6:19 pm 
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Hi folks,

Decided to put my new processing tricks to works. Here's a reworking of the original data used above. From the full 4096 x 4096 pixel image (here) a 1024 x 1024 pixel version:

    Image

      M13 - The Hercules Globular Cluster

and here's a 100% crop:

    Image

Improved star colour and sizes from my previous attempt although at 100% I'm seeing too many ringing artefacts for comfort, generated during a very light deconvolution step in PI. But then I won't be sharing at 100%. :P Whoops, warts and all, I just did. It looks better from a distance. ;-)

Bob.

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Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sat Dec 08, 2012 7:00 pm 
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The 100% looks rather too harsh for my tastes, would a lower level of deconvolution been an option? Appying a blur helps even if it takes away the sharpness.

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PostPosted: Sat Dec 08, 2012 7:30 pm 
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Hi popo,

Difficult to have applied a much lower level. Three passes with a StdDev of only 0.7 in PI's Deconvolution tool. I judged it worthwhile because the image really wasn't processed with the intent to offer anything like a 100% view. I did actually use a very light Gaussian blur on the 100% crop. Deconvolution was the right decision, however, as it significantly improves the image at 50% (or smaller) by which time the ringing artefacts have largely disappeared into the ether. 8)

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sat Dec 08, 2012 7:32 pm 
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Hi popo,

Difficult to have applied a much lower level. Three passes with a StdDev of only 0.7 in PI's Deconvolution tool. I judged it worthwhile because the image really wasn't processed with the intent to offer anything like a 100% view. I did actually use a very light Gaussian blur on the 100% crop. Deconvolution was the right decision, however, as it significantly improves the image at 50% (or smaller) by which time the ringing artefacts have largely disappeared into the ether. 8)

Bob.

P.S. Tonight's another bust, with the forecast cloud rolling in. Aargh!

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sat Dec 08, 2012 8:15 pm 
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I haven't seriously played with the deconvolution tool in PI yet...

It's clear for now... noting nearby on satellite images so should be good for several hours. I feel guilty as I didn't put anything out to cool, and it'll take forever before it's really ready. Forecast suggests clouds wont be until after midnight...

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