M27 test

[puckja]

I was testing a new scope with M27. As usual my shots use only short integration time. It was 7 x 60 sec with Lodestar color. After stacked in DSS, I croped the edges, Wipe with Aggressiveness of 91% and some normal flow, then I got the results below.

Wipe aggressiveness 91%

m27_f4_60s_cal_16b_stack7_ST2.jpg (129.98 KiB) Viewed 7512 times

Or link to Astrobin: http://www.astrobin.com/60802/B/


Initial look seems to show some shadow feature that I normally didn't see with my short-time shots. However, by comparing with some other longer shots at Astrobin, I confirmed that those feature inside M27 are valid:
http://www.astrobin.com/18127/


If I did wipe with less agressiveness (50%) and did not stretch too hard under Develop, then I got a different results, which is much smoother inside M27 and it is more "traditional" look.

Wipe aggressiveness 50%

m27_f4_60s_cal_16b_stack7_ST3.jpg (128.84 KiB) Viewed 7512 times

Or link to Astrobin: http://www.astrobin.com/60802/0/

It seems there is quite a bit play and range on the wipe setting which may either smear or stress the brightness transition features in a DSO. I would like to see what do you think about 1)which one is better and 2)your experience on using wipe. Thanks!

[admin]

It seems there is quite a bit play and range on the wipe setting which may either smear or stress the brightness transition features in a DSO.
I would like to see what do you think about 1)which one is better and 2)your experience on using wipe.

You've just discovered why (and how) the Wipe and Contrast modules are closely related!
And you've also discovered why you'd want to mask out any DSOs (depending on their size and the aggressiveness used) when using Wipe (see last two tutorials) so they *don't* get affected like that in the Wipe module.

Wipe's primary purpose is to look for gradients and color bias. For rapidly changing gradients a high aggressiveness may be required, so that Wipe can detect this localized rapid increase/decrease - the aggressiveness parameter governs a window around each pixel, within which Wipe looks gradients. In well calibrated data typically no gradients are detected and a very low aggressiveness suffices, which just removes color bias.

The Contrast module's workings are closely related to that of Wipe's and here its workings are actually used to perform the effect that you describe - local contrast optimization. If you want to achieve this 'side effect' of Wipe and use it to full effect, it is highly recommended to use the Contrast module instead. It leaves color alone and yields more accurate data for the Tracking feature to base its decisions off (this is because different assumptions are used on why you use either module - Wipe is assumes its job is *recovering* the true data that lies underneath gradients and light pollution, whereas Contrast assumes it is *manipulating* the true data).

To answer your question about 'which one is better', I would have say #2, not because it's looks better (noone can be the final judge of that), but because the tools were used as intended according to your personal artisitc vision.

As a side note, have you tried the Read Noise compensation parameter in order to reduce the slightly mottled look of the background?

When all is said and done though, this is a respectable M27 by any standards!

[puckja]

Thanks a lot for your in-depth explanation and your opinion on the results. I used to mask out the DSO at center as you have done in the M33 tutorial. However, in on of my shots with large ccd chip and heavy vignetting, I found that WIPE always leave some residual "vignetting" (some circular gradient from center if "Temporary AutoDev" is on. In that dataset (alibi small DSO at center), I got flattened result only if I use full mask.

That was the reason why I didn't use mask on this M27 data. However, I re-do it with your advice by masking out M27. The brightness undulation inside M27 was reduced and render smoother look. This is the newer version with 75% WIPE:

m27_f4_60s_cal_16b_stack7_ST4.jpg (67.72 KiB) Viewed 7499 times

I was pretty amazed on how much detail this Lodestar color cam can acquire in only 7 minutes AND how much StarTools can help to present the details effortlessly. In my other cam, I need to use 3X more time to get close.

One more question: I found out after WIPE with high %, the background is a little bit "too dark" (the shadow was set too high). And no matter how much I add "Skyglow" there wasn't much change at all. Also, CONTRAST didn't make any change at all. I wonder if that was the sign to indicate too aggression wipe?

Thanks a lot for your time and reply!

[admin]

Wow, nice work! That background looks better too!

One more question: I found out after WIPE with high %, the background is a little bit "too dark" (the shadow was set too high). And no matter how much I add "Skyglow" there wasn't much change at all. Also, CONTRAST didn't make any change at all. I wonder if that was the sign to indicate too aggression wipe?

Could you explain a little about what you mean by 'the shadow was set too high'? Indeed, if Contrast doesn't do much with the default values then that means local contrast in the larger structures is already optimal (for that particular Aggressiveness setting).

[puckja]

Sorry for my vague/wrong language. I meant that when the minimum threshold setting on the histogram normal stretch was too high, the background looks "too black" and flat. I cannot add back more brightness to the background easily. If I use more "Digital Development", then the bright part in M27 is over exposed. If I use "Skyglow", it does not have any effect even with slider to the max. So I wonder if that was the consequence if I WIPE too aggressive.

Here is my raw data if you would like to see what I meant:
https://dl.dropboxusercontent.com/u/554 ... stack7.tif

Here is log. You can see that I came back several time playing with Digital Development setting...
--- Crop
Parameter [X1] set to [6 pixels]
Parameter [Y1] set to [6 pixels]
Parameter [X2] set to [746 pixels (-6)]
Parameter [Y2] set to [574 pixels (-6)]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [50 %]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [Yes]
Parameter [Precision] set to [512 x 512 pixels]
Parameter [Dark Anomaly Filter] set to [10 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [80.28 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [76.34 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Wavelet Sharpen
Parameter [Intelligent Enhance] set to [Yes]
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [8.0 pixels]
Parameter [Amount] set to [100 %]
Parameter [Small Detail Bias] set to [75 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [80.00 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Compensate Gamma] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Aggressiveness] set to [75 %]
Parameter [Dark Anomaly Headroom] set to [15 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [74.37 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [StarTools True Color Constancy]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Dark Saturation] set to [4.50]
Parameter [Bright Saturation] set to [3.60]
Parameter [Saturation Amount] set to [122 %]
Parameter [Blue Bias Reduce] set to [1.00]
Parameter [Green Bias Reduce] set to [1.00]
Parameter [Red Bias Reduce] set to [1.00]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Wavelet De-Noise
Parameter [Scale 1] set to [90 %]
Parameter [Scale 2] set to [90 %]
Parameter [Scale 3] set to [91 %]
Parameter [Scale 4] set to [0 %]
Parameter [Scale 5] set to [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [3]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Redistribution Kernel] set to [4.5 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [75 %]
--- Repair
Parameter [Radial Samples] set to [32]
Parameter [Sub Sampling] set to [4x]
Parameter [Algorithm] set to [Warp]
Parameter [Grow Mask] set to [0 pixels]
---
Parameter [UNKNOWN] set to [Hybrid, Keep Stars]
Parameter [UNKNOWN] set to [0 pixels]
Parameter [UNKNOWN] set to [15 %]
Parameter [UNKNOWN] set to [0 %]
Parameter [UNKNOWN] set to [70 Arc Minutes (55' x 42')]
Parameter [UNKNOWN] set to [9]
Parameter [UNKNOWN] set to [1.0 pixels]
Parameter [UNKNOWN] set to [67 %]
Parameter [UNKNOWN] set to [1.00]
Parameter [UNKNOWN] set to [0 %]
File saved [C:\Lodestar\2013_1016\m27_f4_60s_cal_16b_stack7_ST4.jpg].

[admin]

Puck,

Any chance you could upload a single sub?
I'm detecting some odd things in your data (halos around stars, the data seems stretched, a noiseless blotchy background). I'm wondering what's causing this...

[puckja]

Ivo:

You had a great eye! The color undulation may came from the acquisition software for Lodestar color (lodestarc_usb.exe from SXCCD). I also find out there seemed to be some color artifact if I save it as 16-bit TIF. My problem is that I cannot find other software that can correctly debayer this CGYM secondary-color pattern. AstroArt 5 works if you use "CGYM Saturation" mode and (0,2) in the offset. (BTW, AA5 will vertical flip the data) However, AA5 also left some color noise like hot pixels so I didn't use it.

The single frame is here:
https://dl.dropboxusercontent.com/u/554 ... 60s_07.FIT

Defect map instead of dark frame subtraction was used to remove hot pixel. It is because other quirk of this software so that defect map works for me. After defect map fixing, it was debayered and I move up the minimum threshold of the histogram up slightly. I assumed that the data was still linear.

Thank you for looking into my data. Your time is precious and I appreciate it.

Puck