Clear Sky CLS Filter (1.25") by OVL
A good value, quality Light Pollution Deep Sky Visual and CCD Photography Filter from OVL (Optical Vision Ltd, the official Skywatcher distributor in the UK and Western Europe).
This filter is similar to other brands' CLS or UHC filters, it blocks night glow and airglow, sodium and mercury emissions (but not UV or IR). This versatile broadband filter is suitable for all objects, whether you are viewing them with your eyes, or capturing them with your camera. Suitable for visual observations and for CCD photography.