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Old 06-10-2014, 06:08 AM
hobbit
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Am I stacking correctly?

I am consistently have having issues in all my imaging attempts.

Using pixinsight
1. Use one of my HA images as reference and then register all other images to that one.
2. stack and integrate the HA, O3, S2 separately
3. add the separate integrated files in startools as RGB
4. ???
5. fail. I always end up with stacking artifacts and absolutely crappy looking images.
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  #2  
Old 06-10-2014, 06:54 AM
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lazjen (Chris)
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Are you applying darks (and maybe flats) to each image before stacking?
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Old 06-10-2014, 08:19 AM
hobbit
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yep all calibrated
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Old 06-10-2014, 09:10 AM
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There should be no issue with Startools, but have you tried doing the RGB combine in PI?
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Old 06-10-2014, 09:12 AM
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Unfortunately that's not something i've figured out how to do yet.
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Old 06-10-2014, 12:08 PM
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Narrowband colour combination is easy in PI... Invoke the LRGBCombine process with the narrowband images as the R, G & B (untick L.) Use SII for R, Ha for G and OIII for B if you want Hubble palette. The little round global apply button at the bottom left of the process is the one you have to click on.

A screen stretch (Ctrl-A) will now show you what you have in your colour image. It will probably be very green because the Ha is usually brightest. Bring up the STF process and untick the little chain icon at top left then select your image and type "Ctrl-A" again to do an unlinked stretch. That will show you a result with more balanced colour.

Cheers,
Rick.
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Old 06-10-2014, 12:59 PM
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Thanks Rick. That's worked much better (except for bright purple stars) but when I save it only saves the unstretched version. How do I save the completed image?
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Old 06-10-2014, 01:18 PM
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Magenta star halos are normal, alas It takes some effort to get rid of them.

To apply the screen stretch to the image is pretty easy but complicated to explain... First make sure you have STF set up to track the currently selected image: the tick box at bottom right should be enabled. Now click on your screen stretched image (STF will now reflect the screen stretch parameters.) Bring up the HistogramTransformation process, click and hold the new instance triangle on STF and drag and drop it on the bottom bar of the HT process (the bar with the new instance triangle, apply square, etc.) You should see a stretch appear in the bottom panel of HT. Now apply this stretch to your image by clicking and holding the new instance triangle on HT and drag and drop it on your image. The image will turn completely white because it now has an image stretch and a screen stretch applied to it. Turn off the screen stretch by right clicking on the image and selecting Screen Transfer Functions->Reset STF. Voila!

Cheers,
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Old 06-10-2014, 01:31 PM
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Mucho Gracias.
That just seems unnecessarily complex
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Old 06-10-2014, 01:41 PM
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Normally you would probably have those processes on the workspace and set up, so it's really just a matter of two drag & drop operations and one click to disable the screen stretch. It makes sense once you understand what is going on, but it is a bit scary if you're new to PI.
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Old 06-10-2014, 04:53 PM
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No,no,no. For NB, process each filter masters separately in Startools in isolation. tweak em each how you like with total disregard of final colour balance, that's the beauty of NB, it's all arbitrary. Startools saves them as tiff, s then load the tiffs in PS as LRGB (ha,SII,ha,OIII) and curve to taste. Don't treat NB anywhere as rgb until PS.
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Old 06-10-2014, 08:28 PM
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If it's arbitrary, why the "No, no, no"??

DT
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Old 06-10-2014, 09:23 PM
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Watch the free tutorial on Astrodon site for narrowband processing using Photoshop. That is the best I have used but that is Photoshop based.

Greg.
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Old 06-10-2014, 09:47 PM
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If you've got PixInsight though, I suggest really trying to get to know it. It should be able to do everything you need. Check out the PixInsight forums, plus the tutorials on Harry's Astro Shed (http://www.harrysastroshed.com/pixin...sighthome.html).
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Old 07-10-2014, 12:38 PM
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Hi Hobbit,

Do you have any sample data to show what you mean? Or is this related to my NGC6188 post? I am reading this thread with quite some interest as I also struggle to align images, however +1 for Fred's comment. I find it *much* easier to edit the NB data separately and then RGB combine in PS (along with spot re-touching).

If only I could work out how to align between editing the NB channels and then RGB-combine in PS. Would CCDstack be the best option?
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Old 07-10-2014, 12:52 PM
hobbit
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Hey Meru,
Your 6188 data was just the latest. one, however Ricks advise has set things straight. Well straighter.
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Old 07-10-2014, 04:41 PM
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Quote:
Originally Posted by DavidTrap View Post
If it's arbitrary, why the "No, no, no"??

DT
Well, only because any processing like "RGB" before PS is irrelevant and a pain. The rest (not aligning) is arbitrary. Processing for noise etc is far easier seperately.
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Old 07-10-2014, 04:43 PM
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Quote:
Originally Posted by Meru View Post
Hi Hobbit,

Do you have any sample data to show what you mean? Or is this related to my NGC6188 post? I am reading this thread with quite some interest as I also struggle to align images, however +1 for Fred's comment. I find it *much* easier to edit the NB data separately and then RGB combine in PS (along with spot re-touching).

If only I could work out how to align between editing the NB channels and then RGB-combine in PS. Would CCDstack be the best option?
To align the 3 filter masters, I just align the 3 in CCD stack, align only, nothing else. If Ha is bin 1 and the others bin2, CCD stack fixes that automatically at this final align.
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