Recently saw reviews of the Antlia dual band filter (
https://www.testar.com.au/products/a...SABEgJOa_D_BwE) at $599 from Testar and wondered how users had found it compared with other choices. With a 5nm bandpass in both OIII and Ha, the Antlia certainly seems like a good choice for mid-level light polluted areas such as mine.
But I have also read some interesting discussions about the effect of focal ratios on the bandpass shift issue. I will be imaging mainly at F5 or F6 so I expect the impact to be minor. But, I’d appreciate any suggestions for alternatives that are perhaps not so bloody expensive.