ORIGINAL DATE: 2021 August 29 UPDATE 1 Aug 2023. Removed UVR Optics NIR-Block because not strong enough at OD2 in some regions. Replaced with reccie for BG39. UPDATE: 22 May 2023. Added suggestion for finding Schott/Hoya UV dual bandpass glass now that UVIR*Optics has gone out of business. UPDATE: 22 May 2023. Added AndreaU MK II and UVBplus to Name Brand Filter list.\ UPDATE: 9 April 2024:  Added warning about Tangsinuo not providing the filter thickness requested by the cus