Having recently moved back to OSC I have a set of 2inch 7nm Optolong Narrowband filters in very good condition. These currently go for somewhere around $1000 for the set new.
These are a good set of filters but you will get some halos on bigger stars which can be fixed if you know how to process out. A great set to get started in the world of Narrowband.
Image of Rosette nebula taken with these:
https://www.astrobin.com/rm7gtj/
$500 posted in Australia
