- Parfocal for systems f/4.0 or slower
- Transmitted wavefront better than 0.25 waves/inch
- Parallelism: less than 30 arcsec
- Made in America
- H-Alpha 3nm Narrow Band Filter
Chroma SII 3nm Narrow Band Filters
Chroma SII 3nm Narrow Band Filters are essential for imaging objects, like nebulae, that are rich in ionized sulfur atoms. These line emission filters work extremely well in heavy light polluted areas and allow you image on nights when the moon is up.