The Optolong Clear Focusing Filter is designed to pass the visible spectral region (420nm-680nm) with 98.5% transmission
Use of astrophotography filters, especially narrowband filters, often results in dim images which can be difficult to focus. Clear focusing filters can be used first to clearly focus the image.
Acts as an outstanding dust shield, which prevents the possibility of dust settling on the lens during long time exposure.
WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.