AstroCoto

I'm using the ultra-narrowband f/10 to f/3.5 set in 1.25" size mounted on a QHYCFW3S-SR. Certainly I wasn't expecting those results but as it is the first time that I use a reducer + FW etc maybe I got something wrong (distance to the reducer maybe?) that might be contributing to the halos . I don't know, I will try different configurations though to see if I can get rid of or at least reduce the halos somehow and report back here. Cheers

Thank you for sharing yours. And yes, you're absolutely right, but it's not as obvious and once you combine the OIII with the H-alpha is barely noticeable if at all while the halo from the SII stays in the final image and is really annoying. But again yes, the halo in OIII is kind of in the limit and surely a problem with brighter stars.

Hi, I'm getting halos as well with the new Baader Ultra-Narrowband filters but in my case is even worse with the SII one. Below a side by side of 450s subs taken with an Evostar 72ED with flattener-reducer and a QHY183m. From left to right, SII, H, OIII. And integrations of NGC 7000, the only operations performed are a linear fit referenced to SII and auto-stretch. The brightest star is 3.70 magnitude and the SII filter is already showing a halo. No halo with the OIII though. From top to bottom, SII, H, OIII.