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  1. #1
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    Default NGC 3628 w/full moon

    Hi guys,

    I'm posting this for one reason. This was imaged last night with the full moon only about 20 degrees away. I know a lot of us image under less than ideal conditions from the 'burbs and/or city with really bright skys. Well, if you pick a relatively bright target and take enough exposures (5.5 hrs in this case), you can get fairly decent results. It's awfully difficult to do color under these conditions, so just stick with B&W. For reference, the background level for each exposure is about 9800 adu with a 10" LX200 OTA and ST8e (not a particularly sensitive camera). It would definitely benefit from more exposures, but it started snowing this afternoon, so I guess that's not likely to happen any time soon. (Star spikes added w/software.)

    Anyway, don't let mediocre conditions or a bright moon keep you from imaging!

    [edit 3/1/11] - I added 6 more hours of data last night. It significantly improves the SNR in the dimmer areas and allows a bit more aggressive processing in the bright areas. "Significant improvement" is probably in the eye of the beholder ;~) My experience is going much beyond this amount (11.5 hrs) adds very little to my eye. The black point has been set on a laptop, so no guarantees it's right.


    Jim
    Attached Images Attached Images
    Last edited by Jim McMillan; Mar 1, 2011 at 20:55.

  2. #2
    Join Date
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    Default

    This is very pretty, Jim. I like B&W imaging myself, probably because that's all I remember ever seeing in S&T from (many) years ago and when roaming around the Adler Planetarium as a kid.

    I hurriedly read your line about mediocre conditions as "medicare conditions," which I thought was perfectly appropriate! Good thing I read the line a second time.
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    H-alpha, BVRI, RGB & Clear filters
    FOV ~15’ x 10’



  3. #3
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    Default

    Jim,

    I've been playing a bit with star spikes using the "star diffraction spikes medium stars" using the Astronomy Tools plugin for Photoshop (v.6).

    Yours are pretty. Mine are pretty ugly.

    How do you fine tune how much spike you want to create? When I run the script, there's no interrupting at any place - it runs to completion and creates a mess, even for just the bright stars, which I would expect to have had very appropriate and very modest spikes. Mine are too ugly to even show here!

    And how do you exclude a spike being produced on a central galaxy core?
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    H-alpha, BVRI, RGB & Clear filters
    FOV ~15’ x 10’



  4. #4

    Default

    Dick

    You asked the very question I was about to ask - I see the exact same thing.
    Rather than the tasteful diffraction spikes that Jim has in his images, I get big, fat, unrealstic (think "magic fairy dust") spikes.

    Hopefully Jim will tell us the secret

    Russ
    Russell Archer
    LX200 ACF 12in, SXVR-H9, SX AO-LF, SX Lodestar, SX FW

  5. #5
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    Default

    Hi Russ, Dick.

    I don't think I do anything particularly unique. As Dick says, the script just runs to completion with no input from me. I use it because I don't like the look of my big stars - particularly in color. To me, the spikes "cover up" the ugliness of the big stars.

    I use the "fat" stars option to add spikes...the "medium" one tends to put spikes on too many stars for my taste.

    If there is a secret, it might be this: what you do to the stars before you add spikes affects the results. Here's a couple of observations:

    1) I use Ron Wodaski's debloomer (it's a MaxIm plug-in) versus MaxIm's built-in debloomer. I find the stars hold up much better to additional processing - although you still have to be careful.

    2) I generally avoid using any of ddp's sharpening processes. It tends to do bad things to the stars - particularly if they bloomed. I might selectively sharpen the main target while avoiding the stars, (generally unsharp mask) in PhotoShop Elements.

    3) I usually use Astronomy Tools "make stars smaller" before adding the spikes.

    4) To "selectively" add spikes, Astronomy Tools has a "=per selection only" tool. The way you use it is to select what you want to add spikes to (usually by selecting the galaxy, then doing an inverse), run the "star spikes fat stars" tool. This will put spikes on everything. Then run the "=per selection only" tool, which will remove any spikes in the unselected area.

    5) If you're getting spikes that are too fat, maybe try the "medium" one, but select only the stars you want using the technique above. That may tone down the spikes a little.

    Hope that helps.

    Jim

  6. #6
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    Default

    Thanks, Jim, for these hints. I'll try them. Do you do the work on your FITS image or on a JPG version (which is what I'm trying)? Maybe that's my problem.
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    H-alpha, BVRI, RGB & Clear filters
    FOV ~15’ x 10’



  7. #7
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    Hi Dick,

    PhotoShop Elements will load 16-bit images, but requires converting to 8-bit to process. So, I load the .fits into Elements, convert it to 8-bit and process from there. I do save it in .tiff format until I'm completely through with processing so there is no data compressing. Converting to .jpg is the last step before posting.

    Alternately, you can convert to .tiff in MaxIm to load into PhotoShop. I don't think it makes any difference which way you do it. I would stay away from .jpg until the last step.

    Jim

  8. #8
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    Thanks, Jim
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    H-alpha, BVRI, RGB & Clear filters
    FOV ~15’ x 10’



 

 

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