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Carbon star T-Lyr and saturation

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#1 bill w

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Posted 10 September 2007 - 12:33 AM

here's a quick study in color saturation for me
was checking out a few carbon stars the other night
T-Lyr looked metallic red in my 8" SCT

here's a very conservative linear process of T-Lyr
attempting to recreate the color:

Posted Image
here it is stretched with an aggressive increase in saturation using a layer mask, and a slight hue shift:
Posted Image


FS102, IDAS LPR, SX-AO, H9C; 60x15 sec.
Los Alamitos, CA 9/2/07.

unfortunately all my attempts to stretch the image and bring out some of the background stars
rendered the star orange as the red level was maxed, and the only way it can be brightened above the background stars is to bring up the blue and green levels.

#2 ayiomamitis

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Posted 10 September 2007 - 04:20 AM

Hi Bill,

The thread brought an immediate smile to my face since I also have a little ongoing project surrounding carbon stars: http://www.perseus.g...Star-Carbon.htm ... and which includes T-Lyr.

After a non-linear stretch, one must indeed saturate to bring up the proper colour since the Lum during layering will wash out the RGB layer. I usually go for around +30 on the saturation and which provides me with a good net result.

#3 chrysalis

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Posted 10 September 2007 - 04:24 AM

Bill, I like the processed version, even if it is a bit more orange than you would like....the soft glow is just wonderful.

:question: ... if it's not heresy, can you keep the second (processed version, cut out ONLY T Lyrae, fix it, and then paste it back where it belongs :question: ?

#4 nik hodges

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Posted 10 September 2007 - 05:00 AM

very cool image

#5 EricCCD

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Posted 10 September 2007 - 07:25 AM

Very nice, Bill! You can always use layer masks in PS to bring out the very red star among the dimmer background stars. Of course, you'll need to be careful to make sure it still looks natural among the other stars.

Eric

#6 bill w

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Posted 10 September 2007 - 12:03 PM

thanks for the comments all

mark, it is heresy! but i'll give it a try, or i can do it with layer masks so we avoid the ugly paste word ;)

eric i tried boosting the saturation with a layer mask, and using a layer mask for the color, but not in normal mode. i'll see if i can get it a bit more red that way.

anthony, that is funny. i had observed most of the stars you imaged when i took the T LYR shot. the thing is that to my eye, T-LYR, and a few of the others are really a very deep, almost stoplight, red. even with your saturation boost, T-LYR comes out very orange. tell me what you think visually.

#7 bill w

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Posted 10 September 2007 - 02:13 PM

ok here's a composite
using a layer mask to bring the linear on to the composite
then selective curve to the star and saturation
trying to preserve the color i see in the eyepiece
thanks for the suggestions
Posted Image

#8 jgraham

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Posted 10 September 2007 - 03:12 PM

Excellent! I've tried off'n on to image colorful doubles, but the saturation problem has been tough to deal with. I can get bright or colorful, but not both.

#9 chrysalis

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Posted 11 September 2007 - 04:49 AM

Still a standout image and the beginning of a compendium of images of these types of objects ;) !


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