Off Axis H-Alpha Prominence Filter System ST600ERFOA

Your O.D. Measurement: 5 5/8” (143mm) to 5 7/8” (149mm)

ERF Aperture: 1.25”

System does not work for Newtonian reflectors the focus travel is to limited. (Focus is extended out 3 1/8’’) with the minimum is f/15 cannot be achieved. Spectrum Telescope does not offer a system for Newtonian reflectors.