A German company developed a new generation of higher quality Nebulae filters.
The Filters known on the market using cheap not polished glas, showing as result stars not as pin point stars, but more a bit astigmatic and the coatings are not live time durable and can be scratched during uncarefull cleaning.
In germany now such filters produced which using high quality polished optical quality showing stars pion point and using durable di-electric coatings which cannot be damaged.
Also the transmissions at the peaks are typical higher between 96% and 98%
UHC and O III , 1.25" Modells each $ 99
UHC and O III, 22 Modells each $ 199