SHO filters set is matched with astronomical monochrome CCD, DSLR(digital camera) to shoot astronomy objects with single channel. These filters set are commonly used by Astrophotographers to present their photos in Hubble Palette. This filter set includes H-Alpha 7nm, SII 6.5nm, OIII 6.5nm cover the lines of emission 656.3nm, 671.6nm, 500.7nm high transmittance so that to obtain the maximum contrast of nebulae while cutting out background emission and suppressing star lights. 

Manufacturing Technique
Fine-optically polishing for double-sides—— Ensure accurate &#955;/4 wave front and <30 seconds Parallalism over the both surfaces
Ultrasonic wave cleaning substrate with purified water—— Clean up by 13 purified water tank to remove impurities and dust effectively
Iron source assisted coating—— For durability and resistance to scratching, as well as stability on CWL (central wavelength) no deviation affected by temperature change.
Constantly stringent quality testing processes—— Each filter was tested by spectrophotometer and laser interferometer testing spectrum and wave front to ensure market filter is qualified product

Specifications
CWL(centre of wavelength): H-Alpha 656.3nm/SII 671.6nm/OIII 500.7nm
Fwhm: H-Alpha7nm/SII 6.5nm/OIII6.5nm
Tpeak: <85%
Optical Density: OD 3
Surface Quality: 60/40
Transmitted Wave front RMS: &#955;/4
Parallelism(arcsec): 30s