I’m moving on these filters bought recently second hand. They are all Astronomik 2” 6nm narrowband filters from 2008 and do show halos around bright stars (see image below). This image shows what I think is one of the more extreme cases in which halos occur (the brightness of the hot blue star Nair Al Saif, the image was taken under a very full moon with a ZWO ASI1600MM-Pro which is not known for its anti-reflection coatings, it was taken with a fast(ish) f4 8” Newtonian, and I have not done any post-processing of the halos). While the halos are certainly the result of the filters (these filters are no longer under any kind of warranty from Astronomik) you can still capture quite stunning detail and can crop as required (see cropped M42). Under better conditions, or some post-processing, I’m sure you could achieve better results. The filters are priced accordingly. The cheaper 2” narrowband filters (with slight higher 7mm bandpasses) sell for around $320 a filter and I’m selling these Astronomik’s for $120 each or $350 for the full set. Postage at buyers expense or pickup in Moorooka, Brisbane.
