There are least 4 Ha filter manufacturers: Coronado, Thousand Oaks, DayStar and Lumicon. Which product depends on what you want to see on the sun, and that depends on the bandpass of the filter. In a nutshell the narrower the bandpass, the more surface detail viewable.
Coronado and DayStar make narrower bandpass filters (less than 1 angstrom). Both prominences and fine surface detail (filaments, plages, sunspots) are viewable.
Thousand Oaks and Lumicon make wider bandpass filters (typically 1.5 angstroms). Only prominences on the sun's limb, and some of the larger surface sunspots are visible.
Coronado and DayStar make narrower bandpass filters (less than 1 angstrom). Both prominences and fine surface detail (filaments, plages, sunspots) are viewable.
Thousand Oaks and Lumicon make wider bandpass filters (typically 1.5 angstroms). Only prominences on the sun's limb, and some of the larger surface sunspots are visible.
