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ASTRO: NGC 4449 colour



 
 
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  #1  
Old June 5th 07, 08:18 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Posts: 2,269
Default ASTRO: NGC 4449 colour

This is the colour version of my NGC 4449 shot. The RGB still had strong
blue parts, but when I did the LRGB combine the blue almost vanished. At
least I can't blame my city skies for any deficencies here as NGC 4449 (at
least the "main" part) is bright enough to give good signal even under city
skies.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 25x5 minutes for L, 3x5 each at 2xbinning for RGB and Ha.

The picture can also be found at
http://ccd-astronomy.de/temp/4449colourgut.jpg

Stefan

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  #2  
Old June 5th 07, 10:24 PM posted to alt.binaries.pictures.astro
Richard Crisp[_1_]
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Posts: 985
Default ASTRO: NGC 4449 colour

when ever you apply luminance it tends to desaturate the color

so the trick is to make the color super saturated when processing before you
apply the luminance.

that's one of the reasons I prefer to avoid luminance

besides it is only a hack to save time. you can get a better image by taking
unbinned RGB and skipping the luminance but it takes more time than shooing
a lot of unbinned luminance and adding binned color to it.


"Stefan Lilge" wrote in message
...
This is the colour version of my NGC 4449 shot. The RGB still had strong
blue parts, but when I did the LRGB combine the blue almost vanished. At
least I can't blame my city skies for any deficencies here as NGC 4449 (at
least the "main" part) is bright enough to give good signal even under
city
skies.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 25x5 minutes for L, 3x5 each at 2xbinning for RGB and Ha.

The picture can also be found at
http://ccd-astronomy.de/temp/4449colourgut.jpg

Stefan



  #3  
Old June 5th 07, 11:35 PM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 4449 colour



Stefan Lilge wrote:
This is the colour version of my NGC 4449 shot. The RGB still had strong
blue parts, but when I did the LRGB combine the blue almost vanished. At
least I can't blame my city skies for any deficencies here as NGC 4449
(at least the "main" part) is bright enough to give good signal even
under city skies.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 25x5 minutes for L, 3x5 each at 2xbinning for RGB and Ha.

The picture can also be found at
http://ccd-astronomy.de/temp/4449colourgut.jpg

Stefan

------------------------------------------------------------------------


Very nice!
Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

  #4  
Old June 6th 07, 12:13 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: NGC 4449 colour



Richard Crisp wrote:

when ever you apply luminance it tends to desaturate the color

so the trick is to make the color super saturated when processing before you
apply the luminance.

that's one of the reasons I prefer to avoid luminance

besides it is only a hack to save time. you can get a better image by taking
unbinned RGB and skipping the luminance but it takes more time than shooing
a lot of unbinned luminance and adding binned color to it.


"Stefan Lilge" wrote in message
...

This is the colour version of my NGC 4449 shot. The RGB still had strong
blue parts, but when I did the LRGB combine the blue almost vanished. At
least I can't blame my city skies for any deficencies here as NGC 4449 (at
least the "main" part) is bright enough to give good signal even under
city
skies.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 25x5 minutes for L, 3x5 each at 2xbinning for RGB and Ha.

The picture can also be found at
http://ccd-astronomy.de/temp/4449colourgut.jpg

Stefan


In theory I agree. But under my skies that's just not the case. I
usually take 8 to 10 lum images but only 3 or 4 are used. Seeing is
just too rotten for the rest. It takes me two to three nights an object
right now as I have only a couple hours of dark a night. I'd need 20
minute sub frames to go as deep with filters as without. That would
mean many more nights than three with seeing very different each night.

When I started color I was having a lot of trouble with LRGB with the
RGB looking a lot better for the color, and for open clusters it is
still the best if the stars are rather bright as they tend to be in most
open clusters. But for everything else I'm getting a much better
looking final image by going the LRGB route. Color actually is better
in the LRGB than RGB though a lot of that is due to the far less time on
color. It might change if I were to spend a week per image. With my
weather of late that would mean no imaging. With LRGB I can take the L
images with the object nearest the meridian and thus best seeing then
take the color frames when it is lower without loss of detail. With
objects much below -10 declination this is about the only way I get
anything useful.

So to me while time is one reason it isn't the only one for going LRGB.

For instance, I've attached the RGB used for the image of NGC 5033 with
the saturation right where it was for the posted image. The color of
stars is deeper, mainly because they aren't overexposed as they are on
the L image without the filter. As they near saturation color does
fade, RGB or LRGB. But then there are far fewer stars in the RGB image.
Mainly though notice the tremendous loss of detail as these were taken
much lower in the sky where seeing is awful.

Of course for narrow band it is the only way that would work at all and
one reason I've not looked into filters other than H-alpha. Now if I
had better seeing and less extinction when low it would be a different
story.

Rick


--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

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  #5  
Old June 6th 07, 02:38 AM posted to alt.binaries.pictures.astro
Doug W.
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Posts: 264
Default ASTRO: NGC 4449 colour

Both versions look great Stefan... Detail is impressive.

--
Regards, Doug W.
www.photonsfate.com
"Stefan Lilge" wrote in message
...
This is the colour version of my NGC 4449 shot. The RGB still had strong
blue parts, but when I did the LRGB combine the blue almost vanished. At
least I can't blame my city skies for any deficencies here as NGC 4449 (at
least the "main" part) is bright enough to give good signal even under
city
skies.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 25x5 minutes for L, 3x5 each at 2xbinning for RGB and Ha.

The picture can also be found at
http://ccd-astronomy.de/temp/4449colourgut.jpg

Stefan



 




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