Optolong SII-CCD 12nm Deep Sky Imaging Filter 1.25" for CCD Astro Photography
This premium Optolong Narrowband SII filter (Sulphur II for CCD) is designed for CCD imaging of deep sky objects and nebulosity allowing 12nm bandwidth of light centered on a wavelength of 672nm through, which corresponds to SII emission lines, and reducing the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). SII emits at 672nm (to be precise: at 671.6nm and 673.1nm) and it is a red colored filter. Many images of planetary nebulae and supernova remnants are taken with H-alpha, OIII and SII filters (such as the famous “Pillars of Creation” or M16, Eagle Nebula) They show great structural details, but have natural colors, looking like an RGB image.
Main Use and Performance
Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants when used with large telescope with low focal ratio. Suitable for viewing or imaging of bright nebulae like M42 Orion Nebula in heavy light pollution. When using visually, use it with a large aperture telescope under clear and dark viewing conditions with good seeing.
Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. In most cases, they increase the contrast between nebula and night sky, not brightening the nebula.
Optolong filters are not designed for solar observation. DO NOT LOOK AT THE SUN WITH ANY OPTOLONG FILTER as permanent eye damage will be the result.
- Schott substrate material
- Glass thickness 2.0 mm (1.25”/2”/36mm)
- Surface Quality: 60/40 (Refer to MIL-O-13830)
- Fine-optically polished to ensure accurate 1/4 wavefront and < 30 seconds parallelism over both surfaces
- 90% transmission at major OIII line 495.9nm and 500.7nm
- Precision off-band blocking, specifically the major emission lines of artificial light pollution (i.e. Na 589nm, Hg 435nm and 578nm).
- Ultra-thin filter cell minimise vignetting by maximising possible clear aperture (clear aperture is 26mm for 1.25” size and 45mm for 2” size)
- Aerometal Material
- Precise CNC Machining
- Sand Blasting Process
- Black Anodized Finish
- Extinction Treatment to Prevent Reflection
- Laser Engraving No Fading
- Standard 1.25” & 2”
- Round 36mm Unmounted
- Plastic PP Case
- Imported High Pressure EVA Case Lining
- Silver Cardboard Box
- High Density Sponge Carton Lining
- Multi-layer anti-reflection coating
- Non-cementing optical substrate coating
- Electron-beam gun evaporation with 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. (Please note, "planetary rotation system" is a type of optical coating process and does not refer to the astronomical system describing the motion of the planets in our solar system.)
The Major Emission Lines of Nebulae: H-α 656.3nm, H-β486.1nm, OIII 495.9nm, OIII 500.7nm, SII 671.6 and SII 673.1 nm
The Major Emission Lines of Artificial Light Pollution: Hg 435.8nm, 546.1nm, 577nm, 578.1nm, Na 598nm, 589.6nm, 615.4nm, 616.1nm