A 50.8mm Round Narrowband Enforced 3.5nm H-alpha Filter by Baader Planetarium:
This 50.8mm round Enforced-Narrowband filter introduces imagers to the extremely narrow 3.5nm H-alpha realm. Enforced contrast supplies increased signal from even the faintest nebula detail. To make such supremely narrow filters, extreme coating uniformity and very high Center Wavelength Precision are necessary. This filter has been designed with these factors in mind.
OPT Product Number: BA-FHALNE-RD50