1. This is a multi-band pass filter that transmits a high percentage of light in the visible spectrum
2. Used in telescope eyepieces to reduce light pollution
3. Anodized housing, high quality metal ring, threaded, blue glass lens
4. These filters enhance contrast when observing brighter objects such as the moon and planets
5. It has a gentle effect of darkening the background of the night sky so that darker objects can be seen more clearly in the darkness of space
6. Effectively filters out selective wavelengths of low-pressure sodium and other artificial light sources
7. Fits standard size 1.25 inch eyepieces and accessories
8. Lens material: pure optical glass lens
9. Sleeve material: metal
10. Aperture: 0.94 inch / 24mm
11. Caliber: 1.25 inch / 31.7 mm
12. Total length (including the external thread): 0.39 inch / 10mm
13. Total length (excluding external thread): 0.28 inch / 7mm
14. Weight: about 7g