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Messages - ChoJin

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1
Gallery / Re: Cygnus Bubble & Crescent Nebula
« on: 2018 August 01 00:24:33 »
stunning!

2
General / Re: Star problem: colors and appearance
« on: 2018 April 05 04:25:27 »
did you try using arcsinh instead of the histogram transform?

3
General / Re: getting L* back into RGB- failing
« on: 2018 March 18 12:35:16 »
Juan said you shouldn't use LRGBCombination on linear data in general.

4
General / Re: getting L* back into RGB- failing
« on: 2018 March 17 13:50:27 »
I agree with you, and the only explanation I could come up with is that LRGBCombine is not doing the same thing than ChannelCombine, but I didn't take the time to read the code to figure out exactly how they differ

Hopefully someone will explain further, Juan? Vicent?

5
General / Re: getting L* back into RGB- failing
« on: 2018 March 17 10:18:14 »
This is not what Juan and Vicent said though. I know authority arguments aren't really good arguments, but I haven't seen detailed arguments from them, but considering the source, I'd tend to listen to them ^^

6
General / Re: getting L* back into RGB- failing
« on: 2018 March 17 04:31:56 »
The original flow was correct:
- stretch L
- stretch rgb
- extract L* from the stretched RGB and linearfit it to fit the Stretched L
- ChannelCombine the fitted L* back to RGB (you unselect all channel but the L and drop the icon to the stretched RGB image)
- use LRGBCombine to merge the stretched L with the (fitted) RGB image

The idea is to match the Stretched RGB with the Stretched L before LRGBCombine.
From what I gathered from this forum (from' Juan), it is important to do so to prevent from noise issues.

7
Gallery / Re: M31 DSLR
« on: 2018 March 12 22:41:54 »
thanks!

8
Gallery / M31 DSLR
« on: 2018 March 12 04:52:00 »
Yet another M31 photo. My childhood dream.

This is the first light of my Skywatcher Quattro 250mm/1000mm f4 with my unmodded Canon 6D.
This is also my first astrophotography with my own gear.

Taken from the Aubrac region in France on August 2016, which has a lovely dark sky. No pollution filter.

It took me forever to process, starting over from scratch 3 times. I spent so many hours on it, I only see the flaws... I guess it's time to stop and let it go ;-)

1h59 with 2 and 5min subs.

All the details can be seen on the description from my flickr.

https://www.flickr.com/photos/-chojin-/38946513840/

9
General / Re: Dark frames and DSLR's
« on: 2018 March 10 11:41:50 »
Thx!
this gives me a pretty good picture of the setup.

10
Image Processing Challenges / Re: Yet another m42 image
« on: 2018 March 08 01:25:46 »
are you sure you didnt push the denoise too much and lost details?

11
General / Re: ArcsinhStretch and White Center in Stars
« on: 2018 March 05 02:29:37 »
this is what I eventually did: I masked the inner core of the stars during deconvolution and that fixed it. I used STF with modified sliders to focus on highlights when experimenting with my core mask.

12
thanks, I'll try the global bright.
NB: funny coincidence, I had your book at my 2nd place and I just got it back today. I'll read again that part, it's been a while  O:)

13
General / Re: Processing Question: Where did the color go?
« on: 2018 March 04 06:07:28 »
@dpaul I'm currently experimenting with combining the arcsinh and HT stretches with a (star)mask and some pixel math magics (ideas taken from https://pixinsight.com/tutorials/NGC7023-HDR/index.html , the "High-Contrast, Small-Scale Structures" part). It seems to work great to get my star's shapes and colours back. They don't look like flat discs anymore.

I've also seen in another topic someone doing RGB stretch with arcsinh and L stretch with HT and LRGB combination to combine them. I haven't tried that yet.

14
General / Re: Processing Question: Where did the color go?
« on: 2018 March 02 15:55:04 »
arcsinh is indeed great for color preservation, but unfortunately like maskedstretch you lose contrast compared to a HT stretch

15
General / Re: ArcsinhStretch and White Center in Stars
« on: 2018 March 01 00:04:25 »
I get white centers too on my image i'm currently processing, but only with the version I have applied deconvolution to the L channel. With my data the stars looks fantastic when stretching the data without prior deconvolution.

I'm going to try doing the stretch in multiple passes (with a mild first stretch, and non-linear stretch afterward, possibly with a mask on those later stretches).

Otherwise I guess I'll go with the PixelMath-way, to combine the "with deconvolution" and "without deconvolution" versions.

I'll see how it goes...

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