ZWO OIII 7nm Filter - 1.25" Mounted

ZWO OIII 7nm 1.25-inch Filter is a budget-friendly OIII narrowband filter (1.25"). Passbands: OIII 500.7 nm (7 nm).

Best for isolating emission lines with a mono camera and filter wheel.

Choose filter size around the sensor diagonal, telescope speed, and filter-wheel or drawer geometry. Flats are still required; a filter can improve contrast, but it will not rescue tilt, bad focus, or poor calibration.