BarleyIsCool

I have the Altair Sii/Oiii and I use it along with an L-Ultimate for Ha/Oiii. They do send a spectral response chart with it and it shows the exact mid-band and width. The width is just under 4nm and the midpoint is about 1nm higher than spec. That is my specific filter, your's may be different when you get it. I use a 2600MC-Pro camera and I split off the red from each filter as the Ha and Sii respectively. Then I average the G+B from each filter to create the Oiii. I then process the three images as if they came from a mono camera and three filters. The nice thing is that you get double the Oiii to for improved SNR in that channel which is typically much weaker than the others (depending on target of course). Here is the HorseHead colored as HSO with about 4 hours of exposure on each filter, so 4 hours of Ha and Sii and 8 hours of Oiii. This is with a WO-Z81 scope.