Done some reading in the archives. Seems the PST does a reasonable job and the next step is quite expensive - ie adding a second filter (double stacking).I see that HOughy is taking delivery of a Lunt 60mm double pass unit in October. Think I'll wait to see how that goes before investing. I guess with a double pass the amount of light transmitted is very much reduced but there is plenty anyway? I've been trying to find out how this works without success - is it by internal reflection, mirrors or what?
(Might be silly questions but best way to learn).
Rog
