I can see a few images of Landolt fields being taken when I’m next back in La Palma. Let’s see, I’ve RGB&Luminance filters, pretty pictures for the taking of (and which I’ve used precisely once, on M57, just to see whether they work); Johnson-V which is by far the most used for VS work; Sloan g, r and i (only ever used the second for production work, though i was once used as an experiment to see whether it improved contrast of Jovian surface features). A “H-alpha + continuum” is in there too, but it’s never been used because I’m not interested in either visual work or in taking pretty pictures of H-II regions. Two slots are empty — one will remain that way and I’m tempted to get a Star Analyser SA200 to play with.
Any suggestions as to what other photometric filters may be worth purchasing, possibly part-funded by selling off the ones I don’t use?