Something really odd is going on with the dataset. I cannot get it to open to show anything useful on any of the applications (OS image viewers, The GIMP) I have here. It's a good demonstration of why TIFF (aka "Thousands of Incompatible File Formats") support is so hard to nail down. Only ImageMagick's display utility showed something recognisable. I can see it's a 32-bit TIFF though with an alpha channel (for some reason). Is this output, straight from DSS?
When I load it into StarTools, the image is entirely black and I cannot see any highlights (e.g. over exposing stars). This is likely the cause of our problems. It could be I have a bug in StarTools. I will investigate.
For the time being, I converted the dataset into a 16-bit TIFF;
Code: Select all
convert Test.TIF -depth 16 +compress Test16.TIF
Opening this gave me something more recognisable that is congruent with a linear dataset. However, unless you imaged under exceptionally dark skies, the dataset's background levels seem to have already been calibrated by something. I cannot see any background bias levels, as usually caused by the various sources of skyglow.
Nevertheless, processing from there was reasonably straightforward. Below is an extremely simple flow that you will recognise as similar to most flows in tutorials, videos, etc.;
--- Auto Develop
Default settings. To see what we're working with.
We can see some stacking artifacts, a defective sensor row, noise, a gradient, oversampling and tracking error.
Trading "useless" resolution for a better signal.
Parameter [Scale] set to [(scale/noise reduction 25.00%)/(1600.00%)/(+4.00 bits)]
Image size is 1300 x 866
Getting rid of stacking artefacts.
Parameter [X1] set to [3 pixels]
Parameter [Y1] set to [17 pixels]
Parameter [X2] set to [1295 pixels (-5)]
Parameter [Y2] set to [862 pixels (-4)]
Image size is 1292 x 845
Get rid of Gradient. Default settings, except parameter [Dark Anomaly Filter] set to [5 pixels] just in case to make sure dark anomalies (e.g. the defective sensor row and any dark noise) is disregarded as representative of the real background level.
--- Auto Develop
Now that the gradient is gone and no longer requires dynamic range to describe it, we can do the final stretch.
Default parameters works ok, with two tweaks.
Parameter [Ignore Fine Detail <] set to [6.0 pixels] to make the detail detector blind to fainter fine noise.
Parameter [Shadow Linearity] set to [8 %] to allocate less dynamic range to the background.
You should - hopefully - notice Alnitak is kept under control very well, while still allocating plenty of dynamic range for the other detail.
Usually worth a try. StarTools - thanks to signal evolution Tracking - tends to have a good handle on how far it can go without the signal falling apart. The earlier binning will have increased the signal-to-noise ratio sufficiently to recover some detail.
The auto mask generator is not working perfectly here, possibly because of the pre-calibration.
I semi-auto generated one like so; Mask > Auto > FatStars preset, set Fiter Sensitivity to ~ 5. > Do. Now click "Grow" three times. Finally click Invert to create "gaps" where stars are that need ignoring.
Back in the Decon module, I just used the default parameters.
... more to taste ...
You can use the HDR module, the Contrast module, the Sharp module, etc. to taste as well
Final color calibration. As you're used to DSS, I chose the Legacy preset. Which emulates the way "classic" application desaturate the highlights.
The default color balance StarTools came up with was sufficient. But you can make sure in the MaxRGB mode that any dominant green can be ascribed to noise and is not readily visible. There are exceptions of course (e.g. O-III dominant emissions such as M42's core). Once you are satisified that any spurious green is not due to an incorrect color balance, you can set [Cap Green] set to [100 %] to enforce the removal of any spurious green.
--- Wavelet De-Noise
Switching Tracking off. StarTools has now had the longest time to monitor signal evolution, including its noise component.
Parameter [Grain Dispersion] set to [15.0 pixels]
Parameter [Smoothness] set to [70 %]
You should end up with something like this;
Hope this helps!