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jimao22

20 Oct 2013 22:44



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Am gasit ceva despre motivul aparitiei halourilor (dar la filtrele narrowband) pe site-ul ASTRODON.

 Stars will be smaller with narrower filters, but the effects can be dealt with in processing. Processing will be required even if your bandwidths are the same.  This arises because OIII and SII are much weaker signals than H-a.   OIII and SII data must therefore be stretched during processing to match the intensity of the strong H-a.  Stretching makes those stars larger, often even larger than the H-a stars.  You may have seen magenta halos around bright stars in tricolor narrowband images. This is how they arise, since we often map OIII to blue and SII to red.  Blue + Red = Magenta.   Software methods such as deconvolution prior to color combining can offset some of these effects.  Selective color correction that desaturate magenta is another means to reduce the problem.