ASTRO: M51 colour

Back in April I got some colour data for my M51 image. The luminance has
only a bit more than 2 hours exposure time and sharpened quite strong, which
is more obvious in the colour version. Somehow the noise is less
objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5 minutes each
for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan

Stefan Lilge wrote:
Back in April I got some colour data for my M51 image. The luminance has
only a bit more than 2 hours exposure time and sharpened quite strong,
which is more obvious in the colour version. Somehow the noise is less
objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5
minutes each for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan

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

Much improved over the previous color version you posted a few years
ago. I don't see the noise in my news program but it does show slightly
in my JPG viewer. When the noise in the black and white version gets
colorized it shows up more I have found. My way of dealing with it is
to first use several Astronomy Tools on the color after I run up the
color saturation to horrid op art levels. I run it up at least 50%,
sometimes 75%. Way too high. Then I run "Space noise" and "Color
blotch" removal tools then the light pollution filter to really darken
the background to only 4 or 5 counts. Faint detail in the color image
will seem to vanish but it will reappear when I use it to color the
Luminosity image. Then, before coloring the lum image I do a 1.5 to 2
pixel Gaussian blur of the color data to further reduce noise. Again,
the blurring vanishes when used to color the lum image. This still
gives me the noise from the Lum image but it isn't colorized by the
color image as that is black in the dark part of the image and blurred
out in the brighter parts. Finally, after colorizing the lum image I
bring the saturation down to normal levels. This last step then hides
any remaining colorized noise. This is how I save some images with very
little color data. Without these steps the color image would be horrid.
I don't know how successful it is with your much brighter skies
however. You are in a very different environment than I am!

Once I get a couple "Honey-do" projects out of the way I'll be posting a
color image of NGC 5033 that really used these steps as this is one
faint, and therefore, noisy galaxy. My preliminary run came out far far
better than I ever expected. I need to fine tune the parameters by
running the process a couple more times with tweaks then should have it
ready for posting. Probably tomorrow as it looks like the weather is
not raining today and outside projects have to be finished.

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".

I have now exchanged the version at the website for one that has additional
smoothing both for the lum and the RGB frames.
As usual when I do colour I come up with dozens of versions and the one I
like best changes every few minutes...

http://ccd-astronomy.de/temp/M51colourgut.jpg

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...


Stefan Lilge wrote:
Back in April I got some colour data for my M51 image. The luminance has
only a bit more than 2 hours exposure time and sharpened quite strong,
which is more obvious in the colour version. Somehow the noise is less
objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5
minutes each for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan

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

Much improved over the previous color version you posted a few years ago.
I don't see the noise in my news program but it does show slightly in my
JPG viewer. When the noise in the black and white version gets colorized
it shows up more I have found. My way of dealing with it is to first use
several Astronomy Tools on the color after I run up the color saturation
to horrid op art levels. I run it up at least 50%, sometimes 75%. Way
too high. Then I run "Space noise" and "Color blotch" removal tools then
the light pollution filter to really darken the background to only 4 or 5
counts. Faint detail in the color image will seem to vanish but it will
reappear when I use it to color the Luminosity image. Then, before
coloring the lum image I do a 1.5 to 2 pixel Gaussian blur of the color
data to further reduce noise. Again, the blurring vanishes when used to
color the lum image. This still gives me the noise from the Lum image but
it isn't colorized by the color image as that is black in the dark part of
the image and blurred out in the brighter parts. Finally, after colorizing
the lum image I bring the saturation down to normal levels. This last
step then hides any remaining colorized noise. This is how I save some
images with very little color data. Without these steps the color image
would be horrid. I don't know how successful it is with your much brighter
skies however. You are in a very different environment than I am!

Once I get a couple "Honey-do" projects out of the way I'll be posting a
color image of NGC 5033 that really used these steps as this is one faint,
and therefore, noisy galaxy. My preliminary run came out far far better
than I ever expected. I need to fine tune the parameters by running the
process a couple more times with tweaks then should have it ready for
posting. Probably tomorrow as it looks like the weather is not raining
today and outside projects have to be finished.

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".

the result is quite good

it is always hard to get good results with broadband RGB in bright skies:
the green always seems to get a gradient

that was always the hard thing for me: controlling the gradients in the
green channel


"Stefan Lilge" wrote in message
...
Back in April I got some colour data for my M51 image. The luminance has
only a bit more than 2 hours exposure time and sharpened quite strong,
which
is more obvious in the colour version. Somehow the noise is less
objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5 minutes each
for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan

I have exactly the same problem. I think I did about 10 versions of the
NGC 4647 image I posted yesterday. I change one thing for the better
and something else goes south. Like choosing a telescopes, image
processing seems to be a compromise.

I do agree the new image is better. Gets rid of the color cast that was
in the image as well as noise.

Rick

Stefan Lilge wrote:
I have now exchanged the version at the website for one that has
additional smoothing both for the lum and the RGB frames.
As usual when I do colour I come up with dozens of versions and the one
I like best changes every few minutes...

http://ccd-astronomy.de/temp/M51colourgut.jpg

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...



Stefan Lilge wrote:

Back in April I got some colour data for my M51 image. The luminance
has only a bit more than 2 hours exposure time and sharpened quite
strong, which is more obvious in the colour version. Somehow the
noise is less objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5
minutes each for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan

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


Much improved over the previous color version you posted a few years
ago. I don't see the noise in my news program but it does show
slightly in my JPG viewer. When the noise in the black and white
version gets colorized it shows up more I have found. My way of
dealing with it is to first use several Astronomy Tools on the color
after I run up the color saturation to horrid op art levels. I run it
up at least 50%, sometimes 75%. Way too high. Then I run "Space
noise" and "Color blotch" removal tools then the light pollution
filter to really darken the background to only 4 or 5 counts. Faint
detail in the color image will seem to vanish but it will reappear
when I use it to color the Luminosity image. Then, before coloring
the lum image I do a 1.5 to 2 pixel Gaussian blur of the color data to
further reduce noise. Again, the blurring vanishes when used to color
the lum image. This still gives me the noise from the Lum image but
it isn't colorized by the color image as that is black in the dark
part of the image and blurred out in the brighter parts. Finally,
after colorizing the lum image I bring the saturation down to normal
levels. This last step then hides any remaining colorized noise. This
is how I save some images with very little color data. Without these
steps the color image would be horrid. I don't know how successful it
is with your much brighter skies however. You are in a very different
environment than I am!

Once I get a couple "Honey-do" projects out of the way I'll be posting
a color image of NGC 5033 that really used these steps as this is one
faint, and therefore, noisy galaxy. My preliminary run came out far
far better than I ever expected. I need to fine tune the parameters
by running the process a couple more times with tweaks then should
have it ready for posting. Probably tomorrow as it looks like the
weather is not raining today and outside projects have to be finished.

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".

"Stefan Lilge" wrote

Back in April I got some colour data for my M51 image.......

Great image Stefan!

Reminds me of my recent visual observation at CSSP. Not only could I see the
spiral arms and bridge, but I could see the dim light around the smaller
galaxy. It's surprising what a really dark sky can do!

George N

"Stefan Lilge" wrote in message
...
I have now exchanged the version at the website for one that has
additional smoothing both for the lum and the RGB frames.
As usual when I do colour I come up with dozens of versions and the one I
like best changes every few minutes...

http://ccd-astronomy.de/temp/M51colourgut.jpg

Stefan

That's beautiful, Stefan. Great work.

George

That's a good one... I love the detail you are recording in these shots....
color is okay too... hehe

--
Regards, Doug W.
www.photonsfate.com
"Stefan Lilge" wrote in message
...
Back in April I got some colour data for my M51 image. The luminance has
only a bit more than 2 hours exposure time and sharpened quite strong,
which
is more obvious in the colour version. Somehow the noise is less
objectionable in the b/w version.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 26x5 minutes for L, 8x5 minutes each for G and B, 5x5 minutes each
for R and Ha..

The picture can also be found at
http://ccd-astronomy.de/temp/M51colourgut.jpg
The b/w version is at http://ccd-astronomy.de/temp/m51-26x5gut.jpg

Stefan