The market for astro-stuff is kind of a strange place right now. On one hand, new stuff is being snapped up so fast that it seems like everyone is constantly sold out of stuff, and basic items (like a stupid extra counterweight!!!) are months backordered.
On the other hand, people are constantly upgrading to larger chip sizes and selling off pretty decent stuff (though be warned - UPS destroyed a mount that I shipped, and USPS has, for the time being, sent a camera I sold on a wild-excursion to Hawaii which is not even close to on the way from my place to San Diego - but I digress - like a camera travelling from Maryland to California...)....
Anyway, I also grabbed a 294mm a couple months ago. I already had an Astronomik 6nm H-a, and managed to find a set of Astronomik Deep Sky RGBs and an Astronomik L2 UV filter here on the CN classifieds. Digging around, it seemed to me that Astronomik is probably the best value *for my purposes*, but I don't have any data to say whether they are better or worse than Baader or Optolong. I've used both at various points, and I know my experience with the Optolong L-extreme was bad when there were bright stars in frame, and I've also heard people lament halos with Baader, but I also know that I don't want to spend more for Antlia, Chroma, Astrodon, etc. I've had Astrodon in the past, but think it may be one of those things were they are "better", but whether an individual user gets "better" results may depend more on that user's skill than on anything intrinsic to the filter itself?
I'm trying to stay Astronomik also to minimize the filter offsets even if they are designed to be parfocal; I want to eliminate need for larger focus offsets if use different manufacturer's filters.
Finally, I only really shoot at f/5.6, so felt comfortable buying 1.25" filters.