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By the way, there is a filter that is designed to minimize the CA of a scope or lens, a Lum filter for that purpose, doesn't this help for example to minimize that blue halo or CA then it can be fine?
What iam asking about, if NB with achromatic scopes is just fine and can be done then to my understand that even with NB the colors are also on different bandwidth, i mean it is more apart together than RGB, OIII is in blue region, Ha and SII are almost close to each other, say using N filter which is nearly at green zone, i want to understand more what makes the difference if we neglect color cameras here at all? and if we use the filters separately and re-focusing for each?
Does the mirror then reflect all of them at the same point so that the mirror is doing better than APO top quality optics for example? Say with a mirror scope we don't refocus for all filters?
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