I used to have a set of of Schott glass filters that I received from a professor at the Institute For Advanced Study at Princeton University..I gave them to Barlow Bob if I can get them back I will try experimenting with them I am sure that a sample of GG-420 was included in the set
-------------------- Lunt H-alpha LS100THa/B3400
Rockland Astronomy Club
Member BAA Solar Section
Central Appalachian Astronomy Club
Astronomical League
DSPST,PST & 70mm Coronado Cal K telescope.2.2A
Zeiss 2 inch prism diagonal&Zeiss Zoom EP
2inch APM Herschel Wedge in a 94mm F7 Brandon
14.5 inch f4.2 Starmaster Dob(Zambuto mirror)
TeleView Genisis SDF with 1000 Oaks Glass filter
Zeiss 63mm f13.5 refractor 1000 Oaks Glass filter
Itty Bitty Solar Radio Telescope.
LHRIES Lite Solar Spectrometer