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- H-alpha 7nm 1.25" Filter
- A very narrow emission-line filter
- Permits a 7nm bandwidth of light (focused on the 656nm wavelength) through
- Blocks transmission of contrast-killing light pollution wavelengths
Main Use and Performance
- Suitable for viewing on faint emission nebula of H-alpha line in full moonlight or in severe light pollution.
- Hubble look of images can be made by the combination of H-alpha, OIII-CCD and SII-CCD, such as the famous “Pillars of Creation” (M16 Eagle Nebula).
- Narrowband imaging with SHO set (H-alpha, OIII-CCD, and SII-CCD) can be done with the moon up in heavy light pollution, so your equipment is not sitting dormant for several weeks.
- H-alpha filter is the first narrowband addition to LRGB set for most imagers who blend a black-and-white Ha image into RGB data to enhance structural detail while maintaining natural look.
- Narrowband filter do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, but do not brighten the nebula.
This ultra narrowband 7 nm H-alpha filter is intended to be utilized in color filter wheels that accept 1.25" filter sizes.
- Surface Quality: 60/40
- Transmitted Wavefront RMS: λ/4
- Parallelism (arcsec): 30s
- Schott substrate material
- Thickness 2mm
- Surface Quality: 60/40 (Refer to MIL-O-13830)
- Optically polished to ensure accurate 1/4 wavefront and <30 seconds parallelism over both surfaces
- 80-percent transmission at the h-alpha line 656 nm infrared wavelength 700 to 1100 nm cut-off
- 0.1-percent transmission of off-band, specifically major emission lines artificial light pollution (i.e. Na 589 nm, Hg 435 nm, and 578 nm). Transmission of 0.1-percent is equivalent to OD3 (Optical Density), where high optical density value indicates very low transmission, and low optical density indicates high transmission
- CWL(centre wavelength): 656.3nm
- Fwhm: 7nm
- Tpeak: <85%
- Coating Wavelength: 300-1100nm
- Optical Denisity: OD3
- Non-cemented optical substrate coating
- Electron-beam gun evaporation with low Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL (central wavelength); no deviation affected by temperature change
- Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band
- Ultra-thin filter cell minimizes vignetting by maximizing possible clear aperture (clear aperture is 26mm on the 1.25"; 45mm on the 2")
- Aero-metal Material
- Precise CNC Machining
- Sand Blasting Process
- Black Anodized Finish
- Extinction Treatment to Prevent Reflection
- Laser Engraving No Fading