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ASTRO: ST4000 First Light, Comments & Advise ..TIA



 
 
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  #1  
Old October 19th 09, 07:14 PM posted to alt.binaries.pictures.astro
Joseph Schmosovich
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Posts: 52
Default ASTRO: ST4000 First Light, Comments & Advise ..TIA

ASTRO: ST4000 First Light, Comments & Advise ..TIA
..
....This is my official first light image from my st4000 with
the AO8, coupled to TV-Pronto @f6.8, Mounted on a LX200-Mak,
this is 1ea image of 480sec.. i think the greyscale image looks
ok, but the color is definitly lacking, i am having trouble
squeezing the detail that i see in the greyscale out of the
color image, i have CCDops,a have a demo version of CCD stack
and PhotoShop CS3, i did aquire 8ea @480sec, over the light
dome Dallas and thru my neighbor's (church) resently installed
Polutonium Plasma Arc Parking Lot Warming Lights, i do plan
on getting the Astronomik CLS-CCD to 'help', every attempt i
make at stacking in either CCDops or CCD-Stack turn the color
into real garbage, i must be doing something wrong.. would
appreciate any and all help i could get from you guys, i am
not asking for a tutor, just a start, a boost, TIA...
..
IIIDaemon
www.GasRecovery.net
..
  #2  
Old October 19th 09, 09:06 PM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: ST4000 First Light, Comments & Advise ..TIA

Joseph Schmosovich wrote:
ASTRO: ST4000 First Light, Comments & Advise ..TIA
.
...This is my official first light image from my st4000 with
the AO8, coupled to TV-Pronto @f6.8, Mounted on a LX200-Mak,
this is 1ea image of 480sec.. i think the greyscale image looks
ok, but the color is definitly lacking, i am having trouble
squeezing the detail that i see in the greyscale out of the
color image, i have CCDops,a have a demo version of CCD stack
and PhotoShop CS3, i did aquire 8ea @480sec, over the light
dome Dallas and thru my neighbor's (church) resently installed
Polutonium Plasma Arc Parking Lot Warming Lights, i do plan
on getting the Astronomik CLS-CCD to 'help', every attempt i
make at stacking in either CCDops or CCD-Stack turn the color
into real garbage, i must be doing something wrong.. would
appreciate any and all help i could get from you guys, i am
not asking for a tutor, just a start, a boost, TIA...
.
IIIDaemon
www.GasRecovery.net
.

M42 is about the most difficult target a beginner could pick. M31 is
the other nasty one. It's dynamic range exceeds that of a CCD meaning
you can't use one exposure to get both the core and the faintest
regions. So the best images are made by using say 30 second images for
the core and 5 or 10 minute ones for the rest. You need to check your
raw data to determine the exposure needed that won't saturate the parts
that exposure is to bring out. Then in Photoshop you can combine these
using fuzzy masks into one finished image. Due to your light pollution
levels going for the faint parts may be impossible. So expose for as
long as possible without saturating the core region. Say no more than
50K. Then using masks in Photoshop you can process the core separately
from the rest and merge the two for a final image. In an LRGB image you
will take more L frames than any one color. I usually use 2 L to each
color frame so one round would be 2L and 1 each RGB. Though I may run
10 or more L for a faint object usually 3 of each color is sufficient,
depends on noise however. You can blur the color data quite a bit to
hide noise without harming the final image. I usually use a 1.8 pixel
Gaussian blur to the RGB image before combining with the L.

It appears your core was saturated in the raw luminosity image. At
least the intensity over that region is constant which shouldn't be the
case. There's a lot of detail in that region. Though in the L image it
isn't saturated in the final result it was somewhere along the line.
The LRGB is severely saturated and the black point needs to be raised
considerably as the background is very bright. I shoot for a background
in the 10 to 15 range, it is more like 50 in your image. That totally
wasts the levels between 10 and 50. You want to use as much of the 256
levels you have as possible. Of course the saturation makes that moot
in this case. I don't know what you did that caused the saturation in
the color image.

You need to learn how to use Curves in Photoshop. This is where 90% of
the work is done. Though for a beginner Shadow and highlights will
often give a starting point. These tools are non linear allowing you to
compress the data to shoehorn in the wide brightness range into the 256
levels a computer monitor can display. I use levels (linear tool) only
to set the black point after it has been raised by the other tools and
needs to be reduced again.

Always watch your histogram as you stretch an image to be sure you don't
saturate the bright region of clip the black. Used properly neither
curves nor shadow and highlight tools will do either but watch at every
step anyway as it is a good guide once you learn to read it. When the L
and RGB images are free of saturation and clipping combining won't
change that. The combine will also be free of both.

CCDStack is a highly respected program but one I've not used so can't
comment on it. I'm still learning Photoshop.

The learning curve for image processing is very steep and will take a
while to climb. Except for the dynamic range problem you are off to a
good start.

When dealing with a light dome many resort to narrow band work as it
allows you to go much fainter with emission nebula than LRGB does. For
LRGB lots of subs helps greatly to reduce the noise level caused by the
light pollution. Use of GradientXterminator an inexpensive plug in will
make dealing with the gradients of urban skies rather easy. It is a
powerful yet easy to use tool for dealing with all types of gradients.

Search the websites of the imagers you see in the magazines all the
time. Many have a lot of information on image processing methods.

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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