StarTools

Posted: **Mon Jun 16, 2014 5:59 pm**

Capturing my second ever DSO, I've done (at least) this much wrong:

- Subs taken in June, 53 degrees North
- lots of light pollution
- F/10 scope (brought to f/7 with a focal reducer)
- no guiding
- unmodified DSLR
- I didn't think to centre the target before capturing it

On the bright side, I chose what I think is a relatively bright target (M51), used a light pollution filter, and took dark, flat and bias images.

I had low expectations. Doing the stacking and postprocessing in Nebulosity, I clipped the black a lot. I know it's wrong, and the result is no masterpiece, but it's mine. I was thrilled with the resulting image (export below, you may need to scroll down to see it).

: m51_neb.png (463.15 KiB) Viewed 10052 times

I'm now trying the demo of Star Tools. I'm sure with this dedicated prosprocessing tool it's possible to equal if not improve these results starting with the unprocessed stacked image. Cropping is fine. Autodevelop makes a mess - I'm sure magnifying my imaging mistakes! Using Develop instead and then Wipe, M51 is recognisable, and the background quite dark, but the target is still very faint (sample below).

: M51_startools.png (434.02 KiB) Viewed 10052 times

How can I stretch the histogram? I think only then can I play with sharpening etc. I've tried copying other people's workflows, but I can't seem to make the galaxy look any more substantial. But those other workflows start with better source material.

Thanks.

Posted: **Mon Jun 16, 2014 10:49 pm**

Hi!

From my experience I suggest redoing the Develop after the Wipe. Once I've done this I get a much better image to take further down the processing stream...

Cheers,
Mario

Posted: **Tue Jun 17, 2014 2:15 am**

Hi Animaal
could you post us a link to your data in maybe dropbox so some of us could take a try at processing it to see what we come up with
Che

Posted: **Tue Jun 17, 2014 6:50 am**

Thanks for the replies. I tried performing an Autodevelop after the wipe, but it magnified the noise in the image too much. A manual Develop made very little difference, although it may be just that I didn't hit the sliders' sweet spot.

The stacked file I used is here (warning: 62MB):

https://dl.dropboxusercontent.com/u/349 ... ed_neb.fit

It's a low quality image, Nebulosity needed help to locate the alignment stars.

Thanks.

Posted: **Tue Jun 17, 2014 1:50 pm**

Animaal
I couldn't open the linked file. Actually, it opened, but not as a pic
Che

Posted: **Tue Jun 17, 2014 2:27 pm**

Apologies, I'm not sure why Dropbox is interpreting a FIT file as text.

Here's a link to Skydrive, with the same file.

https://onedrive.live.com/redir?resid=F ... ile%2c.fit

Thanks.

Posted: **Tue Jun 17, 2014 3:44 pm**

I wont be able to look at it until this evening(PDT). Maybe Ivo or someone else can in the meantime
Che

Posted: **Tue Jun 17, 2014 5:47 pm**

Thanks, there's no rush - I won't be able to capture any new images until the skies darken later in the year anyway.

Posted: **Tue Jun 17, 2014 10:17 pm**

Hi, I gave it a shot and this is what I came up with:

: m51_BJD.png (448.29 KiB) Viewed 10010 times

Here is what I did:

Code: Select all

--- Auto Develop
Parameter [Ignore Fine Detail <] set to [4.0 pixels]
Parameter [Outside ROI Influence] set to [5 %]
--- Crop
Parameter [X1] set to [143 pixels]
Parameter [Y1] set to [121 pixels]
Parameter [X2] set to [3794 pixels (-189)]
Parameter [Y2] set to [2588 pixels (-109)]
--- Bin
Parameter [Scale] set to [(scale/noise reduction 70.71%)/(200.00%)/(+1.00 bits)]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [7.5 pixels]
Parameter [Outside ROI Influence] set to [5 %]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [Yes]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [8 pixels]
Parameter [Drop Off Point] set to [85 %]
Parameter [Corner Aggressiveness] set to [75 %]
Parameter [Aggressiveness] set to [65 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.40]
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 [4.0 pixels]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Compensate Gamma] set to [No]
Parameter [Precision] set to [512 x 512 pixels]
Parameter [Dark Anomaly Filter] set to [10 pixels]
Parameter [Aggressiveness] set to [65 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Mask Behavior] set to [De-ring Mask Gaps, Hide Result]
Parameter [Radius] set to [3.0 pixels]
Parameter [Iterations] set to [8]
Parameter [Regularization] set to [2.00 (smoother, less detail)]
Parameter [Mask Fuzz] set to [5.0 pixels]
--- Wavelet Sharpen
Parameter [Intelligent Enhance] set to [Yes]
Parameter [Scale 1] set to [5 %]
Parameter [Scale 2] set to [85 %]
Parameter [Scale 3] set to [95 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [15.0 pixels]
Parameter [Amount] set to [250 %]
Parameter [Small Detail Bias] set to [70 %]
--- Life
Parameter [Detail Preservation] set to [Linear Brightness Mask]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Inherit Brightness, Color] set to [Off]
Parameter [Output Glow Only] set to [No]
Parameter [Airy Disk Sampling] set to [256 x 256 pixels]
Parameter [Airy Disk Radius] set to [32 pixels]
Parameter [Glow Threshold] set to [0 %]
Parameter [Detail Preservation Radius] set to [25.0 pixels]
Parameter [Saturation] set to [150 %]
Parameter [Strength] set to [80 %]
Parameter [Mask Fuzz] set to [25.0 pixels]
--- Wavelet De-Noise
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [95 %]
Parameter [Scale 3] set to [85 %]
Parameter [Scale 4] set to [35 %]
Parameter [Scale 5] set to [2 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [3]
Parameter [Color Detail Loss] set to [25 %]
Parameter [Brightness Detail Loss] set to [11 %]
Parameter [Grain Size] set to [4.0 pixels]
Parameter [Read Noise Compensation] set to [0.05 %]
Parameter [Smoothness] set to [80 %]
--- Magic
Parameter [Mode] set to [Shrink]
Parameter [Mask Grow] set to [3 pixels]
Parameter [Iterations] set to [4 pixels]
--- Magic
Parameter [Mode] set to [Tighten]
Parameter [Mask Grow] set to [1 pixels]
Parameter [Iterations] set to [1 pixels]
--- Magic
Parameter [Mode] set to [Tighten]
Parameter [Mask Grow] set to [5 pixels]
Parameter [Iterations] set to [4 pixels]
--- Color
Parameter [Cap Green] set to [To Brown]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Dark Saturation] set to [4.00]
Parameter [Bright Saturation] set to [8.50]
Parameter [Saturation Amount] set to [200 %]
Parameter [Blue Bias Reduce] set to [1.60]
Parameter [Green Bias Reduce] set to [1.00]
Parameter [Red Bias Reduce] set to [1.47]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Life
Parameter [Detail Preservation] set to [Linear Brightness Mask]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Inherit Brightness, Color] set to [Off]
Parameter [Output Glow Only] set to [No]
Parameter [Airy Disk Sampling] set to [256 x 256 pixels]
Parameter [Airy Disk Radius] set to [48 pixels]
Parameter [Glow Threshold] set to [0 %]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [200 %]
Parameter [Strength] set to [40 %]
Parameter [Mask Fuzz] set to [10.0 pixels]

If I started over again, I would probably bin it to 50% - and use the color module before turning tracking off.
What helped pulling M51 from the noise is the life module with the "isolate" preset.

BTW, in my (also rather limited) experience, light pollution filters do more harm than good when it comes to galaxies (and star clusters, basically any sources that show more or less continuous spectra), especially with an unguided setup (i.e. rather short exposure times) when you want as many photons reaching the sensor as possible. Unless your target already starts disappearing in the sky background - but if light pollution is that bad, you should probably go find a better place or switch to narrow band imaging...

I'm curious to see other users' results, as I did find the data to be rather challenging and think you already did a pretty good job.
Thanks for sharing your data with us!

Benedikt

Posted: **Tue Jun 17, 2014 11:31 pm**

Thanks Che, Benedikt and Mario.

Animaal, if this were my second DSO ever, i'd be well stoked!

Sure, there's things to improve on (tracking is one of them), but, man, you got a galaxy here!

: m51_20140604_235900.jpg (36.42 KiB) Viewed 10002 times

Benedikt is right when he says that LP filters do some harm - mostly with regards to your colour balance (you're then missing a part of the spectrum and no amount of color balancing is going to get it back). That said, I know Mario here images quite successfully with LP filters. Then, there is also the technique of gather luminance signal with a LP filter, and gathering some color information without the LP filter. Combining them at the end should yield (almost) 'correct' coloring.

Regardless, you should be able to still gather decent data on the brighter objects under LP, as you did here.

This is how I processed our image. I guess the biggest difference with Benedikt's version is that I (as he also mentioned) used the Color module at towards the end of the processing.

--- Auto Develop
To see what we got. I can see a blue bias, stacking artifacts, signs of heavy noise, oversampling and tracking issues.
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
To make use of the oversampling/poor tracking. As Benedikt already indicated, we could/should probably bin more.
--- Crop
To frame the galaxy a bit better.
Parameter [X1] set to [477 pixels]
Parameter [Y1] set to [742 pixels]
Parameter [X2] set to [1416 pixels (-575)]
Parameter [Y2] set to [1302 pixels (-46)]
--- Wipe
To get rid of the blue bias and gradients.
I used the vignetting preset.
Parameter [Temporary AutoDev] set to [Yes] so we can better see what the freed up dynamic range lets us do later on.
Parameter [Dark Anomaly Filter] set to [7 pixels] to make sure the noisiness doesn't create 'false' background calibration points for Wipe to latch on to.
--- Auto Develop
The 'real'/final global stretch (you can also use a manual Develop for this).
I created an ROI (click & drag) over M51A and M51B.
Parameter [Ignore Fine Detail <] set to [5.2 pixels] to make AutoDev ignore noise (otherwise it will optimise the stretch to also show the fine noise).
Parameter [Outside ROI Influence] set to [5 %] to make AutoDev ignore anything outside the ROI more.
--- HDR
Reveal preset.
--- Wavelet Sharpen
To taste.
Parameter [Amount] set to [300 %]
Parameter [Small Detail Bias] set to [95 %]
--- Life
Good call by Benedikt to use the Life Isolate preset. It really helps pushing the noise back.
--- Color
Had to reduce the green a little. A good color balance shows the full range of star temperatures, blue/purple outer rims in the galaxy and a yellow core.
Parameter [Blue Bias Reduce] set to [1.49]
Parameter [Green Bias Reduce] set to [1.23]
Parameter [Red Bias Reduce] set to [1.06]
I set Parameter [Cap Green] to [To Yellow] to kill any remaing green color noise.
--- Wavelet De-Noise
Took a bit of tweaking, but the result was much helped by the Isolate preset in the Life module. I settled for the following;
Parameter [Scale 5] set to [90 %]
Parameter [Scale Correlation] set to [4]
Parameter [Color Detail Loss] set to [7 %]
Parameter [Grain Size] set to [11.2 pixels]
Parameter [Read Noise Compensation] set to [8.42 %]
Parameter [Smoothness] set to [71 %]

Hope this helps!

StarTools

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