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Old 29-01-2019, 03:03 PM
Startrek (Martin)
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Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,027
Hi JA
Thanks for replying
Yes Ive watched the Tony Hallas video a few times but apparently he was incorrect on a number of points as mentioned by Ivo Jager ( Creator of Startools ) on his Startools forum in 2014


Quote / un quotes



1/ "Colour Mottle" is not a physical phenonenon or an attribute of a CCD chip. Colour Mottle is introduced into the image by the use of Adobe Camera Raw and its debayering algorithm and noise reduction filters


2/ Dithering is only effective in reducing "fixed Pattern noise" . Tony's colour mottle is simply the result of transformed ( By Debayering ) random shot noise , the colour mottle is never in the same place , so dithering isnt required to fix that
3/ Tony solution to use dithering is just a roundabout way of fixing up his initial error of debayering his frames using Adobe camera raw
4/ Tonys pre processing starts messing with his data in Adobe camera raw which is already debayered and colour balanced, which increases noise,causing his colour mottle
5/ Then he applies chromatic aberration making the data useless for deconvolution

6/ He doing everything on a per frame basis which is worse than if you stacked the image resulting in a higher SNR and smarter noise reduction
7/ He mentions his data is 16 bit but in fact it is 14 bit because it hasn't been stacked yet
8/ At this stage he basically shooting in Jpeg



Ivo Jager final message on this video is Tony is doing a lot of budding astronomers a great disservice here !


JA
I'm still a bit lost with whether to dither or not , basically I prefer to listen and take notice of IIS members ( maybe yourself ) who have had first hand experience with dithering using their DSLRs in the telescope and comparing before and after results in various conditions ( Seeing conditions, Higher outside air temperatures which is the enemy of DSLR's , various degees of guiding error etc..... )


Welcome any further advice and comments on dithering using DSLR's



Cheers
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