Coronado BF5, 5mm 1-1/4" H-Alpha Secondary Blocking Filter for Solar Viewing

The Blocking Filter is the second element in any Coronado H-Alpha system, it is just as crucial to your safety and the system's performance as the front element. Use the following guidelines for selecting which Blocking Filter you need based on the focal length of the telescope being used. If you are switching to a longer focal length telescope your SolarMax system you can purchase blocking filters separately.

There is no advantage for visual use in using a larger blocking filter than required based on the focal length; however, based on customer feedback, we understand that for imaging with telescopes under 500mm fl, the BF10 is easier to use than the BF5. The Blocking Filter is not a stand alone filter. It is an integral part of the Coronado design and cannot be used without a SolarMax series filter on the front of the optical system.

Focal Length <500mm - BF5.
Focal Length <1000mm - BF10.