StarWipe User Manual
Contents
1. e g Gegenschein etc in favour of using the freed up dynamic range for bringing out detail The resulting image may be considered by purists as unnatural However if desired the natural background level may be reintroduced quite easily in Photoshop The Gimp or similar software StarWipe User Manual www siliconfields net Test Cases The following test cases demonstrate StarWipe s potential to enhance images and bring out detail using the various methods at its disposal Circumpolar Star Trails The following test case demonstrates StarWipe s effectiveness in getting rid of extremely severe light pollution Circumpolar Star Trails by Nick Ares source http www flickr com photos aresauburnphotos 2714286479 under Creative Commons 2 0 license Original StarWipe User Manual www siliconfields net Processed by StarWipe The image was processed in 2 passes using the following very aggressive setting mode global window 1 StarWipe has completely eliminated the light pollution and cloud interference StarWipe User Manual www siliconfields net M8 Core The following test case demonstrates StarWipe s effectiveness in bringing out hidden detail M8 Core by Marc Aragnou StarWipe User Manual www siliconfields net Processed by StarWipe The image was processed in 2 passes using the following setting mode global scale 10 window 50 and mode local scale 10 window 2 The first2. e window percentage e evmode channellpixel e nonormalize e maponly e preblur StarWipe only requires the in and mode parameters to be set but experimenting with other values is highly recommended and often necessary An example of usage would be StarWipe in myinfile omp out myoutfile tiff scale 10 window 8 maponly mode global This would tell StarWipe to read myinfile omp process it in global mode and use 10 for the scale value and 8 of the window value The maponly flag tells StarWipe to only output the light pollution map and not the corrected image It also tells StarWipe to write the light pollution map to myoutfile tiff In The in parameter specifies the input file The file should either be a 24 bit or 32 bit RGB BMP file or a 24 bit or 48 bit TIFF file The input image should be uncompressed StarWipe currently does not support any other fileformats A single asterisk may be used as a wildcard to put StarWipe into batch processing mode In batch processing mode output files are written to a file with the same file name but with _wiped appended to it StarWipe User Manual wwwsiliconfields net Out The out parameter specifies the output file The output file is a 48 bit uncompressed TIFF file StarWipe currently does not support any other output formats In case batch processing mode is engaged the out parameter is ignored Mode StarWipe can operate in two main modes gl
3. pass using global mode removes overall light pollution and normalises the image s contrast The very conservative 50 value for window leaves virtually all local contrast unchanged The second pass uses an aggressive window size in local mode to bring out small detail Note in particular the detail in the core 10 StarWipe User Manual www siliconfields net M8 Core The following test case demonstrates StarWipe s effectiveness in reducing light pollution and vignetting M101 by Charles Kuehne 11 StarWipe User Manual www siliconfields net Processed by StarWipe The image was processed in 2 passes using the following setting mode global scale 15 window 5 and mode local scale 10 window 2 The first pass using global mode removes the heavy light pollution and vignetting For global mode a rather aggressive 5 window is used Even more aggressive settings start bringing out details in the arms but also start peeling away the dust The second pass uses an aggressive window size in local mode to bring out smaller detail in the core and arms Glare from the bright core is also noticeably reduced 12 StarWipe User Manual wwwsiliconfields net Acknowledgements The following people have been helpful in assessing StarWipe s usefulness and have kindly donated some of their images to help evaluate StarWipe s effectiveness and illustrate its use e Alan Mehan Australia e Marc Aragnou Aus
4. StarWipe User Manual www siliconfields net StarWipe User Manual Introduction StarWipe is a tool for astrophotographers Its main uses are negating the effects of light pollution and the removal of vignetting It can also be used to enhance contrast locally in images or revealing previously hidden detail it can be used to reduce glare caused by light diffusion in deep space objects or to counter the effects caused by other types of light scattering such as haze terrestrial or non terrestrial StarWipe also enables further processing to extract even more detail from an image making curve manipulation and sharpening algorithms like Unsharp Mask more effective StarWipe can be used as one of the very first tool in the processing chain that is before any stacking aligning or other processing is performed It ensures that all images to be stacked are uniformly lit and there are minimal brightness variations caused by objects drifting into vignetted areas or other light level altering events haze or an inconsiderate neighbour or spouse This should help the stacking and aligning process StarWipe can also be used in a variety of ways as a post processing tool to bring out more detail in a finalised picture or unlocking an end of the road scenario opening up an image to further processing and detail extraction StarWipe is part SiliconFields bigger ever evolving suite of image processing tools plans and schematics for astrophotograp
5. er pixel produces slightly softer results which depending on your preference may be more pleasing NoNormalize Since the lightpollution map is subtracted form the original image the result is a dimmer image StarWipe restores the brightness to its original value by default The nonormalize flag tells StarWipe not to normalize the output This can be useful if the user wishes to restore or enhance brightness by other means such as a photo editing suite image stacker or Siliconfield s StarSqueeze This parameter is ignored when the maponly flag is specified StarWipe User Manual wwwsiliconfields net MapOnly The maponly flag tells StarWipe to output the light pollution map instead of the corrected image This light pollution map image is normally subtracted from the input image to obtain the corrected image and then discarded It directly represents the light that is removed from the image In combination with the inmap parameter see below this may be useful for fast processing of multiple images that were shot under the same conditions It may also be useful to examine or correct the areas that are affected by StarWipe or for other post processing purposes Light pollution map for the M101 image by Charles Kuehne see test cases exported by using the maponly flag InMap Using the inmap parameter StarWipe can be told to use a pre computed light pollution map in an image file instead of calculating a new one If for
6. example you have a lot of files that need to be stacked but they all have the same lightpollution or vignetting problem then it is much quicker to calculate the light pollution map only once and output it with the maponly flag see above Then for every file you can StarWipe User Manual wwwsiliconfields net import that same light pollution map using inmap instead of having to calculate it for every file The inmap maponly combination can also be useful if you feel StarWipe s calculations just can t quite get it right In that case you can export StarWipe s lightpollution map using the maponly flag see where StarWipe went wrong modify it Photoshop or The GIMP etc and reapply it to the image using the inmap parameter One last way the inmap maponly combination may be useful is when you re trying to apply StarWipe to an excessively noisy image and the preblur functionality is unsatisfactory see below In this case take the original image then blur it or use noise removal plug in in Photshop or The GIMP etc until the noise is gone Then feed this image to StarWipe and output the light pollution map using the maponly flag Then feed the original noisy image to StarWipe but using the inmap parameter tell it to use the lightpollution map we just computed using the blurred version StarWipe will now output a properly corrected image PreBlur The preblur parameter blurs the input image before passing it on to the light pol
7. hers on a sub shoestring budget While it also holds potential for more professional users as demonstrated in the test cases it s main purpose is to take advantage of the ever increasing computing and resolving power of consumer personal computers and digital compact cameras and put it to use for the sidewalk asrtonomer While there is no substitute for quality optics professional build quality mounts and dark sky sites some of the problems stemming from a lack of high standard hardware or optimal seeing conditions can now be overcome by software running on comparatively cheap hardware StarWipe was written in too much of the author s spare time and is made available free of charge for personal use If you find this program useful please consider making a donation by PayPal to ivo jager silconfields net Any feedback comments and or feature requests are also welcome at ivo jager siliconfields net and www siliconfields net as well as interesting job and or contracting opportunities StarWipe may be used free of charge for personal use Please contact the author for commercial and or institutional use Lastly please do not redistribute StarWipe without prior consent from the author StarWipe User Manual wwwsiliconfields net Usage StarWipe is a command line tool and takes the following parameters note the double dashes mode globalllocal e in infile e out outfile inmap infile e scale percentage
8. lution detection algorithm Because StarWipe does not deal well with excessively noisy images dead pixels and or other anomalies blurring the image can help smoothen out the unnatural data and keep StarWipe on track The parameter passed is used to define a window size in pixels over which the input will be averaged A small value should suffice to smoothen out noise or other anomalies Because light pollution and contrast differences tend to occur over large areas blurring should not have a great impact on StarWipe s accuracy StarWipe User Manual wwwsiliconfields net Limitations and areas of improvements StarWipe is as of May 2010 a command line tool for Linux and Windows operating systems It does not have a graphical user interface Input and output formats are limited to uncompressed either 24 bit or 32 bit BMP or 24 bit or 48 bit TIFF Depending on settings StarWipe s lightpollution detection algorithm can be very sensitive to bad pixel data such as dead pixels JPEG artefacts or other non natural anomalies in the image StarWipe is most suitable for Deep Space Objects generic wide angle views and screen filling lunar images StarWipe is less suited to other types of astrophotography images and even less so for other types of photography with the possible exception of medical imaging such as X ray and MRI imaging StarWipe especially in global mode sometimes has the tendency to remove natural background light levels
9. obal and local They both employ different algorithms to determine the areas that benefit from contrast improvement Global mode affects large areas of the image and is most suitable for removing light pollution vignetting glare and aggressive detail enhancing Local mode affects smaller areas of the image and is most suitable for bringing out small detail and localised contrast enhancement Local mode is best used with small values for the window and scale parameters Scale The scale parameter specifies a scaling percentage that is applied to the input image before it is processed by StarWipe The scaling down eliminates noise and mitigates artificial irregularities which can confuse StarWipe Depending on preference smaller values can produce a softer effect Additionally smaller values greatly reduce computing times Depending on the application larger or smaller values may be more effective in achieving the desired result Window The window parameter specifies the overall strength of local contrast enhancement versus the rest of the image Smaller values have a greater effect on local contrast In Global mode smaller values may introduce artefacts in the form of fuzzy circles In this case it is best to choose a less aggressive value or it may be appropriate to switch to local mode EvMode The evmode parameter specifies the valuation method StarWipe uses to determine contrast Per channel is the most effective while p
10. tralia e Charles Kuehne United States 13 StarWipe User Manual wwwsiliconfields net Changelog 0 5 e Initial release 0 6 Enhanced lightmap scaler bicubic e Added preblur functionality e Fixed manual e Deprecated excolor functionality Added uncompressed 24 bit and 48 bit TIFF import e Output format now 48 bit TIFF instead of 24 bit BMP e Changed internal processing to 64 bit 14
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