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Old 27-04-2010, 01:11 PM
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Bassnut (Fred)
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Join Date: Nov 2006
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Originally Posted by telecasterguru View Post

Can I just ask, after stacking in DSS (I have CCD stack but haven't come to terms with it yet) I have been processing my images with fits liberator, combining and aligning then doing curves and levels in PS and from what you are saying DL will combine all the colour images in one go and therefore make most of my processing redundant.

Is the stretching of each individual channel automatic?

I like fits liberator because it is free and it is a PS plug in so there is no changing between processing software.

I use Nebulosity as capture software, would you recommend that I switch to DL. It is around $500US I believe.

CCD stack (for mono anyway) is the ducks guts IMO, it can do aligning on the final LRGB subs too. It offers the most contoll of all the apps, but is a bit more manual as a result.

I do all the aligning and deconvolute filtering in it (the decon filter alone is worth buying CCD stack, the single best tool in any app IMO) and then export via fits liberator to PS for combining, levels,curves,sharpening etc .

You can do levels, curves, DPP (some say DPP is best done in astro apps) sharpening etc in most astro apps, but I think PS is the best for these. I dont know what DDS can do.

Importing with fits liberator does most of the streching for you by useing Linear,log or arcsin stretch.

You dont really have to stretch in the astro app, because they offer "screen stretch" to allow you to see what your doing without affecting the original file. I found stretching in DL or CCD stack no where near as good as with fits liberator.

Stretching/scaling via fits liberator is important as it is done in 32bit FITS before converting to 16bit for PS, preserving bit resolution within the reduced dynamic range in 16 bit. If you export each (aligned) LRGB file to PS for combining, then each in turn is stretched seperately by fits liberator, allowing stretch/scaleing tweaking for each. Its an easy proceedure and sort of automatic with a few mouse clicks. There is no manual curveing as such as in PS, the curve shapes are determined by the algorithm selected and histogram end point setting. This fixed stretching is therefore repeatable and you will get a feel after a while which setting work for which images you take.

Stretching only in PS can cause "combing" (spikey histogram and obvious layer transitions due to a compressed dynamic range and then non linear expansion) this is even worse in older 8 bit PS versions.

With carefull algorithim and setup selection of the stretch function in fits liberator, you can avoid the need for much stretching in PS and just do minor adjustment curves.

When you say should you switch to DL, I would say no, not at all, unless you want to do almost all the processing in DL, which I dont recommend, as PS is best suited to processing after aligning IMO (with stretching by fits liberator). PS tools are vastly superior to most comparible processing tools in astro apps (apart from the decon filter).

I use DL for capture but only for capture. Many apps will do capture only.

I then only use CCDstack, fits liberator and PS. These 3 apps give about all the controll you need with ease, albiet a little less automated than DL (but then DL has a bit less control than CCDstack, for stacking/aligning)

Since you already have CCDstack, id be learning that IMO, not buying DL.

Sorry, on a re read, your asking about DL for capture. Well, I recon DL is the best for capture, but it depends on your rig. DL has very a comprehensive Guiding function, automatic unattended multifilter sub capture, dither, auto 1-click scope re-pointing integrated with pinpoint, and a smick AO function and much more.

The built-in processing is very handy during capture actually. You can open a sub you did the night before, click calibrate, and bang, a nice clean pic is right there to align your next imaging run without mucking around finding the right dark, its all automatic.

Last edited by Bassnut; 27-04-2010 at 01:34 PM. Reason: DL for capture
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