H-alpha filters are essential for imaging nebulae and other objects which are rich in ionized hydrogen. At 656.3nm, a narrow-band emission filter is required to separate H-Alpha from the SII doublet (671.6nm and 673.1nm).
- Parfocal for systems f/4.0 or slower
- Transmitted wavefront better than 0.25 waves/inch
- Parallelism: less than 30 arcsec
- Made in America