Advice wanted on my ST attempt at M51

[gminder]

I began my AP addiction a few weeks ago and am trying to settle on primary processing software. I'm on a trial of PhotoShop CC and PixInsight and I have purchased StarTools. Photoshop is well documented and there's no shortage of tutorials. I find PixInsight to be very complex and the developers seem to take pride in maximum complexity and minimal documentation.

I bought ST because the thought of not having to worry about histograms and curves is very appealing. I am struggling though. The attached photo is my best attempt with ST with my M51 data. It's not bad and I'd be happy with it if I hadn't done better with PixInsight. My PixInsight M51 image can be seen at http://www.astrobin.com/full/48539/?mod=none

I think it has more detail and the color is better than what I could accomplish in StarTools. I am posting the ST workflow below. After the de-noise I was flailing about trying to find a tool that would get me what I know is in the data.

I'd welcome any hints to get the most out of my data. If anyone wants to take a crack at it, the FITS file is at https://www.dropbox.com/s/xe8c70bk6xsc2 ... 0Stack.fit

PI Cal Reg Stack_ST Processing.jpg (325.01 KiB) Viewed 8633 times

M51 data details:

C8/AVX
Orion mini 50 guide scope w/ SSAG
Unmodded Canon 450D
37 120s subs calibrated, registered and stacked in DSS with darks only

ST Workflow

File loaded [C:\Users\Gary\Pictures\Astrophotography\M51\12 Jul 13\PI Cal Reg Stack.fit].
---
--- Crop
Parameter [X1] set to [47 pixels]
Parameter [Y1] set to [43 pixels]
Parameter [X2] set to [4240 pixels (-50)]
Parameter [Y2] set to [2814 pixels (-42)]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [0.97]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [94.97 %]
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 [2.0 pixels]
--- Wipe
Parameter [Mode] set to [Correct Color Only]
Parameter [Top End Treatment] set to [Wipe 2.0]
Parameter [Cap Green] set to [To Yellow]
Parameter [Output Gradient Only] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [0 %]
Parameter [Dark Anomaly Headroom] set to [10 %]
--- Wipe
Parameter [Mode] set to [Correct Brightness Only]
Parameter [Top End Treatment] set to [Wipe 2.0]
Parameter [Cap Green] set to [No]
Parameter [Output Gradient Only] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
Parameter [Dark Anomaly Headroom] set to [10 %]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [Top End Treatment] set to [Wipe 2.0]
Parameter [Cap Green] set to [No]
Parameter [Output Gradient Only] set to [No]
Parameter [Precision] set to [128 x 128 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
Parameter [Dark Anomaly Headroom] set to [10 %]
File saved [C:\Users\Gary\Pictures\Astrophotography\M51\12 Jul 13\PI Cal Reg Stack_ST Crop_Dev_3Wipe.tiff].
--- HDR
Parameter [UNKNOWN] set to [Low]
Parameter [Channels] set to [Brightness & Color]
Parameter [Algorithm] set to [Optimize Hard]
Parameter [Dark/Bright Response] set to [1.52]
Parameter [Detail Size Range] set to [18 pixels]
Parameter [Noise Suppression] set to [10 %]
File saved [C:\Users\Gary\Pictures\Astrophotography\M51\12 Jul 13\PI Cal Reg Stack_ST Crop_Dev_3Wipe_HDR.tiff].
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bottom End Saturation] set to [1.00]
Parameter [Top End Saturation] set to [2.80]
Parameter [Saturation] set to [205 %]
Parameter [Blue Ratio] set to [1.00]
Parameter [Green Ratio] set to [1.09]
Parameter [Red Ratio] set to [1.02]
Parameter [Mask Fuzz] set to [1.0 pixels]
File saved [C:\Users\Gary\Pictures\Astrophotography\M51\12 Jul 13\PI Cal Reg Stack_ST Crop_Dev_3Wipe_HDR_Color.tiff].
--- Wavelet Sharpen
Parameter [Channels] set to [Brightness Only]
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 [Brightness Mask Power] set to [0.00]
Parameter [Amount] set to [100 %]
Parameter [Small Detail Bias] set to [80 %]
File saved [C:\Users\Gary\Pictures\Astrophotography\M51\12 Jul 13\PI Cal Reg Stack_ST Crop_Dev_3Wipe_HDR_Color_Sharpen.tiff].
--- HDR
Parameter [UNKNOWN] set to [Medium]
Parameter [Channels] set to [Brightness & Color]
Parameter [Algorithm] set to [Reveal DSO Core]
Parameter [Dark/Bright Response] set to [1.00]
Parameter [Detail Size Range] set to [12 pixels]
Parameter [Noise Suppression] set to [Off]
--- Wavelet De-Noise
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [75 %]
Parameter [Scale 3] set to [50 %]
Parameter [Scale 4] set to [25 %]
Parameter [Scale 5] set to [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Brightness Mask Power] set to [0.00]
Parameter [Color Detail Loss] set to [50 %]
Parameter [Brightness Detail Loss] set to [25 %]
Parameter [Structural Emphasis] set to [0 pixels]
Parameter [Edge Repair Strength] set to [15 %]
Parameter [Noise Tracking Influence] set to [100 %]
Parameter [Intelligent Despeckle] set to [0 %]
--- Magic
Parameter [Mode] set to [Shrink]
Parameter [Mask Grow] set to [1 pixels]
Parameter [Iterations] set to [0 pixels]
--- Color
Parameter [Cap Green] set to [No]
Parameter [Bottom End Saturation] set to [Full]
Parameter [Top End Saturation] set to [Full]
Parameter [Saturation] set to [116 %]
Parameter [Blue Ratio] set to [1.00]
Parameter [Green Ratio] set to [1.01]
Parameter [Red Ratio] set to [1.01]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Life
Parameter [Detail Preservation] set to [Min Distance to 1/2 Unity]
Parameter [Compositing Algorithm] set to [Screen]
Parameter [Inherit Brightness, Color] set to [Off]
Parameter [Output Glow Only] set to [No]
Parameter [Airy Disk Sampling] set to [128 x 128 pixels]
Parameter [Airy Disk Radius] set to [8 pixels]
Parameter [Glow Threshold] set to [5 %]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [50 %]
Parameter [Strength] set to [100 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- HDR
Parameter [UNKNOWN] set to [Medium]
Parameter [Channels] set to [Brightness & Color]
Parameter [Algorithm] set to [Reveal DSO Core]
Parameter [Dark/Bright Response] set to [Full]
Parameter [Detail Size Range] set to [64 pixels]
Parameter [Noise Suppression] set to [100 %]
--- Wavelet Sharpen
Parameter [Channels] set to [Brightness Only]
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 [1.0 pixels]
Parameter [Brightness Mask Power] set to [0.00]
Parameter [Amount] set to [100 %]
Parameter [Small Detail Bias] set to [75 %]
--- Crop
Parameter [X1] set to [416 pixels]
Parameter [Y1] set to [100 pixels]
Parameter [X2] set to [4096 pixels (-97)]
Parameter [Y2] set to [2117 pixels (-654)]

[admin]

Hi,

Welcome to the hobby!
Whether it be PixInsight, Phtoshop or StarTools - you're showing us that you're off to a flying start and I'm frankly amazed you've been able to process your data to the standard that you have within mere weeks of trying the respective software - nicely done!

Thanks very much for posting your workflow and raw data stack - it's the best way of getting people up to speed with ST quickly.

So here's what I did. Note that I used the latest alpha version for this (there are small differences in the way some modules are operated and the results they give you). I'm also not going to Bin the data (which would've reduced noise considerably and made detail recovery much easier) on purpose, just to make thing a little more challenging.

Load the file, and tell ST it is stil linear. As you may or may not know this is the important bit where StarTools starts to track the evolution of your data (including noise propagation), so that it can make optimal decisions on your behalf later on (such as noise reduction and deconvolution and color correction).

The very first thing I always do after loading data I haven't seen before, is run an AutoDev with default values. AutoDev was built to automatically stretch the image globally (!) in such a way that the maximum amount of detail is visible. This is extremely useful at this stage - it shows us any defects, issues or problems that are latent in the data.

Screenshot-Untitled Window.jpg (79.48 KiB) Viewed 8620 times

Indeed, it's showing us a number of issues;

• light pollution - a green cast and background level is readily visible.
• vignetting - the corners darken slightly - flats have not been applied
• dust donuts - most notable in the upper left corner, but where there's one, there's more! also due to flats not having been applied
• stacking artifacts - visible at the top

All these issues can be fixed by StarTools and we'll tackle them one at a time (note that fixing as many of these problems as possible during data acquisition is ofcourse preferred, but it is not always possible or desireable depending on your time, gear and circumstances).

Just go ahead and 'Keep' the result. The Tracking feature will allow you to redo your global stretching as many times as you like, no matter if you have done all sorts of other operations after (it just travels back in time to apply it, changing the past to affect the present and future).

I crop the image, getting rid of the stacking artefacts and framing the object a bit better. Note that it seems I'm just lazily cropping out the fading corners and dust donut as quick fix, but rest assured that their visibility right now is just the tip of the iceberg and we're bound to find more, similar, issues in our cropped version of the image any way - they will need to be dealt with.

Next, it is time to tackle the light pollution and gradient(s). Wipe is indeed the go-to tool for that. I first try the default setting. It will indeed get rid of the light pollution, but the global stretch was performed doesn't show us much of the result.
I 'Keep' the result and run AutoDev again (choose 'Redo global stretch') to see how Wipe did and if there are any other issues left.

Screenshot-Untitled Window-2.jpg (265.76 KiB) Viewed 8620 times

The result is better, but there are definitely some faint echoes of dust donuts visible and I'm not quite happy with the gradient removal towards the edges. Dark anomalies (like dark pixels or dust donuts) will impact Wipe's effectiveness in determining the 'real' background level (as they cause a local 'dip' where there are pixels that are darker than the real background). While they are faint, I will show you how a mask can keep Wipe from sampling their pixels for background level (just like PI's DBE).

As a side note, you may also notice some vertical streakiness (read noise) cropping up. Bias frames could help this and failing that, there is the Band module in StarTools.

I keep the AutoDev result and launch the Wipe module again. I'm going to do a second pass to try and correct the outstanding issues. This time I bump up the Dark Anomaly Filter, and create a mask that has the dust donuts masked out, so that Wipe won't sample them (just use the lassoo tool to circle the dust donuts, creating a non-green gap in the mask). I also use the vignetting preset, as I'm not happy with how the gradients were removed going out towards the edges of the image. All the vignetting preset does is set a different (higher) Aggressiveness for gradient removal towards the edges of the the image. Clicking 'Do' yields the following.

Screenshot-Untitled Window-4.jpg (229.44 KiB) Viewed 8620 times

I'm reasonably happy with the result. Notice how the faint 'finger' stretching out from M51B (or NGC 5195) towards the bottom of the image has been left intact. Note that we can actually remove the dust donust in post-processing as well (see this tutorial).

It is now time to do our 'final' global stretch (e.g. the one we'll use to base the rest of our tweaking on). As you may already know, there are two ways to perform a global stretch. One is to use AutoDev, the other is using a manual Develop.
You can use either to taste, but I'm going to use AutoDev once more. This time I'm going to specify a Region of Interest, roughly marking out the galaxies. This tells AutoDev to just optimize the global stretch for that area. I lower the 'Outside ROI influence' to 2%, indicating that pixels outside the ROI influence Autodev's decisions for optimizing the ROI just slightly. I Keep the result.

Screenshot-Untitled Window-5.jpg (174.39 KiB) Viewed 8620 times

Next, I'm going to apply some deconvolution. Your mileage may vary with deconvolution, especially with noisy data like this, but we're free to try!
Decon by default will assume that any mask we have set is a star mask (it needs a star mask to keep overexposed/singularites from ringing). The mask for Wipe obviously isn't suitable (it's not a star mask), so I click 'AutoMask' which typically does a pretty good job creating a star mask for me in a single click. This image is fortunately no exception.

I play around a little with the Radius parameter. As expected the difference is not huge, but Decon manages to dig out some detail in the inner core of M51 that wasn't visible before; again thanks to Tracking, Decon knows exactly how far it can go without introducing (much) noise, and without you having to worry about creating luminance masks or manual painting techniques. What's more, you'll notice we're applying deconvolution *after* we stretched our data which, mathematically speaking, is a big no-no. Again, Tracking handles the mathematical intricacies in the background, so that you don't have to worry about these things - the (normally very important!) notion of processing linear vs non-linear data has been completely abstracted away from the user in StarTools and is taken care of by the engine.

From here you can apply some HDR optimization (I used the Reveal preset) and some Wavelet sharpening of the bigger scales to bring out the arms a bit more.

The image is still noisy, and while the Denoise routine will take care of this shhortly, there is a way to help getting the noise down while 'lifting' the DSO from the background; the Life module's Isolate preset. It works reasonably well by itself, but it works even better with a mask that helps it find the superstructure of the DSO (see also this YouTube video).

Set Mask Fuzz to Max, strength to 50%.

Finally, we do Color calibration. It's quite simple actually most of the time; find a color balance that shows a good range star temperatures using the Red, Green and Blue bias parameters. Your DSLR is unmodded, so it is normal for blue stars to be a bit more prominent than red stars (due to lack of IR/red response). Orange stars should however be in equal abundance to blue stars. The saturation parameters help you control how dark and bright parts gain color. It is usually desirable to keep the (dark) background in a nice neutral grey. The Dark Saturation parameter lets you define this.

I settled on the following;

Screenshot-Untitled Window-8.jpg (76.21 KiB) Viewed 8620 times

Lastly we switch tracking off and avail of ST's best-in-class noise reduction; you'll notice ST will know exactly where to apply noise reduction (e.g. the background) and where it should back off (e.g. the galaxies' details), all thanks to keeping track of how the data evolved over time. The 1.3.5 alpha versions incorporate an even more effective noise reduction module that exploits pshychovisual traits in human detail perception, making use of available noise ('useful noise') to convey detail, instead of smoothing everything (the latter is still totally possible if desired).

Screenshot-Untitled Window-9.jpg (63.58 KiB) Viewed 8620 times

Finally I apply the Life module's Isolate preset one more time, without a mask and overdriving the saturation a little.

Screenshot-Untitled Window-10.jpg (48.71 KiB) Viewed 8620 times

And this is the end result;

PI Cal Reg Stack_ST135.jpg (145.47 KiB) Viewed 8620 times

From here you could round the stars a little. Or you could decide that the resolution is too high for the detail available and reprocess the image with a binned version (I would probably do that).

Hope this helps!

[gminder]

That is stunning! I can't thank you enough. I will be digesting your workflow to understand what you did. I am a "show me" kind of learner and such a tutorial will really jump start my progress with Star Tools. Thanks!!!

[admin]

That is stunning! I can't thank you enough. I will be digesting your workflow to understand what you did. I am a "show me" kind of learner and such a tutorial will really jump start my progress with Star Tools. Thanks!!!

No problem, let us know how you get on!