Welcome, PixInsight users!

Guides, tutorials, tips & tricks.

Welcome, PixInsight users!

Postby admin » Sun Nov 10, 2013 4:14 am

Hi all,
Over the past year or so, we've been seeing an increasing number of PixInsight users move to StarTools for their post-processing. :text-welcomewave:
Thank you all! It's a big endorsement of StarTools' philosophy on signal processing, signal fidelity, data/input mining and its approach to user interfaces. :D

For you newcomers as a quick-start, I thought I'd try to 'translate' to the best of my abilities PixInsight's modules into their StarTools equivalents. You may also find this useful if you're contemplating going the other way and you're curious about PixInsight and wish to give their 45-day trial a spin. While I (and as it seems many others) have strong views on their ageing linear engine/algorithm design and object oriented UI, PI's excellent pre-processing (stacking) capabilities are still one of the best around and worth the price alone.

As opposed to the moderators of the PI forums, we encourage discussing or even trying other software and how it relates to what we know and use today; it helps us learn and relate to all the different facets of processing, which can only be a good thing.

If you're coming from post-processing in PixInsight, then there are a number of important things that are different/new in StarTools;
  • 'Tracking' plays a very large role in StarTools. This makes workflows much less linear and allows for StarTools' engine to "time travel" between different versions of the data as needed, so that it can insert modifications or consult the data in different points in time as needed ('change the past for a new present and future'). It's the primary reason why there is no difference between linear and non-linear data in StarTools, and you can do things in StarTools that would've otherwise been nonsensical (like deconvolution after stretching your data) in PixInsight. If you're not familiar with Tracking and what it means for your images, signal fidelity and simplification of the workflow & UI, please do read up on it!
  • Tracking how you process your data also allows the noise reduction routines in StarTools to achieve superior results. By the time you get to your end result, the Tracking feature will have data-mined/pin-pointed exactly where the noise is in your image and apply noise reduction only in those areas. Therefore noise reduction is applied at the very end, as you switch Tracking off. This means that StarTools has had the longest possible amount of time to build and refine its knowledge of where the noise is in your image. This is different from other software, such as PixInsight, which allow you to reduce noise at any stage, since such software does not track signal evolution and its noise component.
  • Tracking how you processed your data also allows the color module to calculate and reverse how the stretching of the luminance information has distorted the color information (such as hue and saturation) in your image, without having to resort to 'hacks' like the 'Repaired HSV Separation' script in PixInsight. For more information see here. Due to this capability, color calibration is best done at the end as well, before switching Tracking off. This too is different from other software, such as PixInsight, which wants you to do your color calibration before doing any stretching, since it cannot deal with color correction after the signal has been non-linearly transformed like StarTools can.
  • Traditional histogram stretching and white/black point setting is completely abstracted away. StarTools considers such tools sub-optimal and archaic approaches to image processing.
  • Many tools seems simpler but, in reality, are more powerful. Data mining and analysis does away with parameters that can be objectively determined, or (derivatives of) parameters that you already specified in other modules earlier. As such, truly destructive settings are neigh-impossible to achieve (for example StarTools refuses to clip your data) and objectively optimal constraints are automatically determined from prior input. Luminance masks or local supports are automatically generated and updated as needed without user intervention.
  • StarTools does not treat processing as a linear, object-oriented process (e.g. an implied collection of independent processes), because real image processing carried out by a human emphatically isn't a linear process. In StarTools, as long as Tracking is on, processing steps depend on each other and reuse each other's data, findings and previous user settings. StarTools is all about refinement and shaping of data, where you revisit, rather than reapply modules. A linear, object oriented approach is therefore not possible or even desirable if signal fidelity, noise mitigation and ease of use are paramount. As such you will not find the equivalent of 'process containers', undo histories or similar in StarTools. Instead you'll find a single undo buffer and a 'Restore' button, which will let you negate the contributions that certain operations made to the currently visible end result, regardless of sequence.
  • While some prefer scientific purity of an image (the author included), others like to emphasize aesthetics. StarTools does not try to prescribe what's right and what's wrong in this regard. As such StarTools contains tools like the Heal Module, the Synth module, the Life module (and others) that can be (ab)used to help the user make educated guesses about what plausible data would look like, based on what is already in the image and based on what the user knows is definitely not in the image. Contrary to PixInsight, we take no stance in what should or should not be allowed by including or excluding these tools in the software. Some people like diffraction spikes on their stars, some people don't like stars at all. Some people like to be able to remove dust donuts or fix CCD blooming issues. You decide.

Regarding workflows;
Consult the YouTube videos (particularly the last two) for some standard workflows. However, you'll notice that they all follow the following general order;

  • Load the data (using Open or LRGB), indicate it is still linear (this switches Tracking On).
  • Develop or AutoDev to see what we have got.
  • Fix stacking artifacts with Crop
  • Fractionally Bin the data with Bin if 1 unit of detail does not fit in 1 pixel until it does (or leave some oversampled data for deconvolution if desired and noise levels allow).
  • Wipe away light pollution gradients and signal bias.
  • Redo Develop or AutoDev for final global stretch.
  • Deconvolution
  • Use Contrast (for medium-large) and HDR for (medium-small) local dynamic range optimization
  • Use Sharp (with mask that Deconvolution made) for detail enhancement
  • Color calibration with the Color module
  • Switch tracking off for final noise reduction.

The following table will hopefully serve a quick 'dictionary' to translate PixInsight terminology into StarTools terminology;






















PixInsightStarToolsNotes
ABEWipeUsing Wipe without a mask functions similar to ABE - a gradient/bias model is created based on all pixels in the image.
DBEWipeUsing Wipe with a mask functions similar to DBE. If a large area of the image is covered by a DSO or nebulosity, it is recommended to mask out this DSO or nebulosity, as Wipe may include aspects of the DSO or nebulosity in the background/bias model.
BackgroundNeutralizationWipeAt the same time Wipe flattens the field and removes gradients, Wipe also calibrates the background and removes bias in the color channels. Note that this does not necessarily mean that the background becomes a nice neutral grey. Rather it makes sure that the background is luminance bias-free across all color channels. Subsequent color calibration will modify and neutralize the chrominance (color) information.
AssistedColorCalibrationColorWhile in PixInsight it is mandatory that color calibration is performed on the linear data at the start, color calibration in StarTools may be performed at any time, preferrably closer to the end of your workflow. This is to achieve pure, more scientifically correct color constancy (a more 'compromised' PixInsight style of coloring is also selectable if you're feeling nostalgic). White point references may be selected with a mask or through clicking on the image.
ColorCalibrationColorsee above
Repaired HSV SeparationColorsee above, (StarTools retains color information, rather than trying to recover it from neighboring pixels)
AutoHistogramDevelopDevelop automatically sets the white and black point.
AdaptiveStretch, MaskedStretchAutoDevStarTools employs an enhanced (and much faster) algorithm that yields optimal global dynamic range assignment (without masking artifacts), while being easier to control. Noise may be rejected for optimisation and a Region Of Interest may also be specified.
HistogramTransformationosbsoleteIn StarTools histogram transformations for global dynamic range assignment are considered obsolete and sub-optimal tools. Use AutoDev and Develop instead and optimize local dynamic range subsequently with Contrast, HDR and Sharp.
ScreenTransferFunctionosbsoleteIn StarTools the distinction between linear and non-linear data does not exist. Use Develop or AutoDev to redo your stretch as many times as you like.
LocalHistogramEqualizationHDR, Contrast, SharpLocalHistogramEqualization results can be approximated with the more flexible HDR, Contrast and Wavelet Sharpen modules.
ATrousWaveletTransformSharpIn StarTools Sharp does not clip, allows control over interscale-fighting and is noise-aware.
HDRWaveletTransformContrast, HDRIn StarTools, Contrast nor HDR clip the image and work locally instead of globally, leading to more optimised results.
GradientHDRCompressionHDR
GradientHDRCompositionLayerThe Min Distance to 1/2 Unity and Max Contrast filters in the Layer module will create High Dynamic Range composites from 2 images with different exposure lenghts.
RangeSelectionMask (Auto)In StarTools the Mask editor's 'auto' feature allows for a great variety of automated ways of selecting pixels, including range selection and multi-step mask addition/overlaying.
ChannelExtractionLRGB
ChannelCombinationLRGB
Morphological FiltersLayerSee 'filter type' parameter for a large selection of different filters.
PixelMathLayerIn StarTools, pixel math is performed in the Layer module by means of graphical user interface. A huge range of operations is selectable, while multiple operations can be chained by means of a buffer.
DeconvolutionDeconIn StarTools, deconvolution is noise-aware and is able to generate its own de-ringing mask. De-ringing will still try to coealesce singularities. Deconvolution is StarTools is geared towards dealing with atmospheric seeing-related issues only.
ACDNR, TGVDenoiseDenoiseIn StarTools, noise reduction is applied at the very end when Tracking is switched off. Due to StarTools' noise evolution Tracking noise reduction will much more targeted and no (sub-optimal) luminance masks or local supports are required.


Welcome to the StarTools community and I hope you find this useful in your quest for a better image! Do let me know if anyone would like to see more/different info here. This post will be updated as required.

Clear skies!
Ivo Jager
StarTools creator and astronomy enthusiast
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Re: Welcome, PixInsight users!

Postby torsinadoc » Mon Dec 02, 2013 4:44 pm

Thanks. The table is golden!
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