So you want to try a triband or quad band filter but the dollars stop you. Well you may be in luck. Overtime I looked at the spectral graphs of these expensive filters and I thought maybe I can combine two filters to produce a similar response.
Well as luck has it I had just what i needed. So I took an Astronomik UHC and stacked an Astronomik IR Block and ended up with a quad band equivalent. This UHC filter has a passband of 480nm>506nm and 640nm>and beyond. The Astronomik IR Block has a passband of 370nm>688nm. Stacking them together I ended up with two passbands of 480nm>506nm (Hb+Oiii) & 640nm>688nm (Ha+Sii) thus yielding a quadband filter combo.
I also tried my Idas LPS D1 with the Astronomik UHC and got similar results with the Sii region possibly being suppressed. Instead of a cut off of 688nm with the IR Block the D1 gave a 673nm cutoff. I noticed a little more red when using the IR filter, but not that much to make much of a difference. Off course these wavelength are approximate and will be slightly different for your optical setup due to incoming angle of the image presented to the filters.
These filter combos may not provide the same passbands as the expensive dedicated filters but they sure provide a lot of fun for no additional cost.
Edited by DonBoy, 20 January 2019 - 06:59 PM.