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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 .. |
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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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