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Thread: Which DSS Stretching Formulas are good for What??

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    Default Which DSS Stretching Formulas are good for What??



    I know that DSS is far from being the best Image Processing App out there, but there are times when the Imaging Laptop is the only one with me for a 2-3 day Imaging Weekend and I don't have the CPU Power to run PixInsight against the previous nights haul.
    Which of the several offered DSS Stretching Formulae are best for What types of Results??

    I see nowhere that this is covered in the DSS Wiki...
    But surely the group here has used DSS enough to form opinions and experiences...
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    Default Re: Which DSS Stretching Formulas are good for What??

    To clarify:
    I'm asking about the list of formulas on the left-hand side of each RGB line on the RGB/K Tab of the Image Processing Screen (once a Stack has been Registered and Calibrated and Stacked), which are represented by vertical Math Symbols that you click in order to see the rest of the list of selections.
    The selections are "linear", "Cube Root", "Square Root", "Logarithm", "Log(Log)", "Log(Square Root)", "ASinH".

    I've used Log(Square Root) for my Quick-and-Dirty Stacking Efforts for so long that I can't remember if that formula isn't the Default.

    I've found that while I can Stretch the original Image far enough in DSS to show decent Color and Structure in a Galaxy or Nebula, but only at the expense of totally blown-out Stars. I've seen others Images who list DSS and then CS3 (or other PS version) as their sole Image Processing Tools.
    I'm hoping that there is a "trick" to pulling "decent" images out of DSS, so that I can at least preview and assess the basic quality of my Exposures while still at the Dark Site. Sleeping past Noon leaves only a few Daylight Hours to use for this processing before the next Dusk brings more Imaging, and I'm often quite curious to know whether I captured "Enough" before making that 4-8 hr drive home at the end of the weekend.
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    Default Re: Which DSS Stretching Formulas are good for What??

    DSS is the only stacking program that I use but I do not do any adjustments to the image at all with DSS. I use the autosave tif function except that for me it is the autosave fits file that I load in to Star Tools for post processing. I may do some final tweaks to the image with CS6. The link has a good deal of info on why you should not use the adjustments in DSS.

    How to use the DSS Autosave.tif for best possible image quality

    Edit: I think I may have misunderstood your question, try this link.

    http://asignobservatoryii.webs.com/tutorials.htm
    Last edited by Hondo; 05-09-2014 at 06:34 PM. Reason: Added new link.
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    Default Re: Which DSS Stretching Formulas are good for What??

    Thanks Scott read all 7 pages a good thread started by Phil
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    Default Re: Which DSS Stretching Formulas are good for What??

    Quote Originally Posted by Hondo View Post
    DSS is the only stacking program that I use but I do not do any adjustments to the image at all with DSS. I use the autosave tif function except that for me it is the autosave fits file that I load in to Star Tools for post processing. I may do some final tweaks to the image with CS6. The link has a good deal of info on why you should not use the adjustments in DSS.

    Edit: I think I may have misunderstood your question, try this link.
    I'm familiar with both those resources, and am about as familiar with DSS as the Authors (no digs intended).
    I'm also working up a decent user-level knowledge of PixInsight, and have test-run StarTools. I simply want a lower-impact alternative while In-the-Field with my Imaging Laptop, as I don't want to burn it down simply to see for myself or to show others the "potential" of the previous Night's Imaging.

    My inquiry is specifically about the RGB Formula Options available on the Stretching Tool.
    ES AR152 / ES 80ED Apo / Orion 8in F/3.9 / C9.25-SCT / C6-SCT / C10-NGT / AT6RC / ST-80 / AstroView 90 / Meade 6000 APO 115mm
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    Default Re: Which DSS Stretching Formulas are good for What??

    Hi Siegell it is a pity that what Scott posted was not what you were looking for I hope someone chimes in soon with some insight. I am at a very basic level and found Scott's post very helpful
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    Default Re: Which DSS Stretching Formulas are good for What??

    I can't help answer your main questions as I was never able to figure how not get all my colors washed out so I've just used the autosave file like the rest. I didn't know those options were even there. since that curve couldn't be adjusted I thought moving back/forth would just end up like a hue/tint change and ended up doing everything on the Lum tab since I could modify its curve. i think the stack options kept the channels aligned which is all i thought i needed. Just went in to see if I could find what you were referring to.

    To answer one of your questions it does look like the log sqrt is the default (what mine's set to and I had never changed it). it also appears to reset back to that each time I open it even when I just played around with some of the other options.

    To my non-science eyes it looks like those just change how it calculates the slope of the curve so some are more compressed than others. maybe just looking at the resulting histogram it can be considered something like small stretch vs large stretch? although not sure how to really try to translate that to 'did I get enough data'. Maybe somewhere on the interwebs someone knows what method photoshop uses to create its curve? wouldn't help determine which works better than others but would be something to compare to.

    I ended up opening a final/stretched image just to get the rgb tab to show up and when I went through the options most did havoc. the bottom one -ASin I think was the only one that seemed to keep the colors similar. but I didn't actually adjust anything, just hit 'apply' and it was already stretched so all that might be irrelevant.
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