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NGC 6888 - Crescent Nebula in Cygnus
Dear group,
I have spent the past couple of evenings pursuing the stunning emission nebula NGC 6888 in Cygnus with mixed results. Although successful at capturing the plethora of stars in the region (nearly 8000 stars in my image), I was partially successful in acquiring the dim portions of the Crescent Nebula. For last night's result based on just under five hours total exposure, please see http://www.perseus.gr/Astro-DSO-NGC-6888.htm .... all comments and suggestions welcome! Anthony. |
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NGC 6888 - Crescent Nebula in Cygnus
Anthony Ayiomamitis wrote in news:f7qfn2$as$1
@mouse.otenet.gr: Dear group, I have spent the past couple of evenings pursuing the stunning emission nebula NGC 6888 in Cygnus with mixed results. Although successful at capturing the plethora of stars in the region (nearly 8000 stars in my image), I was partially successful in acquiring the dim portions of the Crescent Nebula. For last night's result based on just under five hours total exposure, please see http://www.perseus.gr/Astro-DSO-NGC-6888.htm .... all comments and suggestions welcome! Its nice looking as usual, but I believe you could do much better on that one, including catching the nebular ghosts around NGC 6888 itself, if you used a H-Alpha filter and used that as luminance. I got a higher level of signal from a an 10x10min exposure in a poorly collimated 200SS under mag 2.5 skies in Belgium. Give it a try, the area doesn't lack bright guide stars anyway. -- Pierre Vandevenne - DataRescue sa/nv - www.datarescue.com The IDA Pro Disassembler & Debugger - world leader in hostile code analysis PhotoRescue - advanced data recovery for digital photographic media latest review: http://www.pcmag.com/article2/0,1759,1590497,00.asp |
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NGC 6888 - Crescent Nebula in Cygnus
Pierre Vandevenne wrote:
Anthony Ayiomamitis wrote in news:f7qfn2$as$1 @mouse.otenet.gr: Dear group, I have spent the past couple of evenings pursuing the stunning emission nebula NGC 6888 in Cygnus with mixed results. Although successful at capturing the plethora of stars in the region (nearly 8000 stars in my image), I was partially successful in acquiring the dim portions of the Crescent Nebula. For last night's result based on just under five hours total exposure, please see http://www.perseus.gr/Astro-DSO-NGC-6888.htm .... all comments and suggestions welcome! Hi Pierre, Its nice looking as usual, but I believe you could do much better on that one, I agree fully there is much more room for improvement. including catching the nebular ghosts around NGC 6888 itself, if you used a H-Alpha filter and used that as luminance. I got a higher level of signal from a an 10x10min exposure in a poorly collimated 200SS under mag 2.5 skies in Belgium. I did try h-alpha the first night out (Astronomik 13nm) and 12x15min exposures but the result was not very much different. Give it a try, the area doesn't lack bright guide stars anyway. This is certainly true and even when imaging in h-alpha. Anthony. |
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NGC 6888 - Crescent Nebula in Cygnus
On Jul 20, 3:09 pm, Anthony Ayiomamitis
wrote: Dear group, I have spent the past couple of evenings pursuing the stunning emission nebula NGC 6888 in Cygnus with mixed results. Although successful at capturing the plethora of stars in the region (nearly 8000 stars in my image), I was partially successful in acquiring the dim portions of the Crescent Nebula. For last night's result based on just under five hours total exposure, please seehttp://www.perseus.gr/Astro-DSO-NGC-6888.htm.... all comments and suggestions welcome! Anthony. Do try it in Hydrogen Alpha - great fun and lots of fine detail to tease out. Martin N http://www.martin-nicholson.info/index.htm |
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NGC 6888 - Crescent Nebula in Cygnus
Anthony,
Well you promised us this one and you certainly made good on your promise. Fine work! Ben |
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NGC 6888 - Crescent Nebula in Cygnus
Ben wrote:
Anthony, Hi Ben, Well you promised us this one and you certainly made good on your promise. Fine work! How about the Iris nebula or the Fireworks Galaxy next? ;-) Anthony. Ben |
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NGC 6888 - Crescent Nebula in Cygnus
How about the Iris nebula or the Fireworks Galaxy next? ;-)
Anthony. Either/or..... How about both? I'm sure they will be as well done as the rest of your captures. Ben |
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NGC 6888 - Crescent Nebula in Cygnus
On Fri, 20 Jul 2007 17:09:07 +0300, Anthony Ayiomamitis
wrote: Dear group, I have spent the past couple of evenings pursuing the stunning emission nebula NGC 6888 in Cygnus with mixed results. Although successful at capturing the plethora of stars in the region (nearly 8000 stars in my image), I was partially successful in acquiring the dim portions of the Crescent Nebula. For last night's result based on just under five hours total exposure, please see http://www.perseus.gr/Astro-DSO-NGC-6888.htm .... all comments and suggestions welcome! Anthony. Wonderful picture. I've been happy with the way this object looks to the eye in my C-11 but of course I don't get the reddish color. I am aware that you defend the ersatz diffraction spikes on the bright stars (I don't remember: do you make them with a software algorithm during processing, or are they acquired by putting threads across your aperture?) But I have two comments: 1. I hope if you are doing the diffraction pattern AFTER the raw data have been acquired, that you are keeping the raw information, sans the artificial artefact. That way, if some day you change your mind, you can redo the picture without the diffraction spike effects. 2. The spikes are rather prominent and cover quite an area. This is sometimes a problem when searching images for latent data in the case of looking for an unknown object or a change in a known one. I have had problems with old film and plate halation patterns -- and diffraction spikes -- covering up areas near bright stars; once I was searching for a change in a faint star near a bright one, and all resources I had at my command had such halation and spikes that it was hopeless to find any old pictures for the purposes of comparison with a newly-acquired one: the artefacts swamped the faint object. Just a thought, in case you want to go searching for things. The other night, in fact, I saw visually a huge, dense pattern of what LOOKED like nebulosity around 4 Cygni, not plotted in the Uranometria. I tested this against other stars of the same magnitude in the region of 10-20 degrees within that star, and none glowed that much. I wrote to Brian Skiff and asked him; he thought there was nothing unusual and suspected merely an instrumental artefact, as I had not - by my admission - been able to measure it instrumentally. I only made visual comparisons, which are notoriously inaccurate. Well, Jaakko Saloranta examined the DSS blue plate after heavy processing, and reports that I probably saw some faint reflection glow that this plate has recorded. The problem is: your diffraction patterns would totally mess that up, so an image done by you in this fashion would not be suitable as a reference for comparison purposes. I've argued this til I am blue in the face, but the advocates of "fake spikes" disagree with me completely, and love 'em. If you want pretty pictures that SEEM to look like ones done years ago by Malin, with heavy unsharp masking, then -- sure -- you can generate this effect to your heart's desire. But, it seems to me tragic that you have a marvelous imaging device that itself creates no spikes or internal reflection artefacts -- and then you ADD them, somehow...why? AstroApp |
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