Baader or Astronomik RGB filters

[MartinB]

I believe the halos with the astronomic type II filters is related to the fact that they reflect unwanted parts of the spectrum rather than absorbing. The glass cover of the slip reflects light back to the filter which reflects light back on to the chip. Features of this type of reflection are that they are quite big and that they appear to be slightly off the optical axis, giving the appearance of a collimation issue. The problem is spacing specific which is why some people get them and not others.

The type II dichroic filters are supposed to have better transmission of light than absorptive filters but this benefit is probably quite small. Much is madel of the spectrum cut of points for each of the 3 colour filters. There is a lot of manufacturer hype here and colour is a very subjective thing at the best of times. The astronomic filters are bomb proof, you wont rub off the coatings when you clean them.

I think the Baader absorptive filters represent great value. Dichroic may have some advantages but these are likely to be small. Whether the antireflective claims for the Baader filters stands up to scrutiny will be interesting to see.