Posted by Richard Miles at 17:47 on 2013 Jul 31
Eliot – Don’t put any other filter like an IR cut-off in front of your V filter.The Astrodon dichroic V filter shouldn’t suffer in damp atmospheres – the problem lies with the Bessell coloured glass version as the BG12 element is hydrolytically unstable. The V filter Norman Walker makes (Nick has referred to this) is an excellent one in that it comprises the standard coloured glass elements sandwiched between 1mm silica plates. I too have one of these as well as the Astrodon dichroic which I have mounted in a Canon 52mm filter holder which drops into a long lens.When I looked on the Baader webpage I couldn’t find the V filter either – Callum’s right though as I have checked out the url he quotes although they are only the 1.25" ones.