Castell OIII Deepsky Filter for 2-Inch Eyepieces
Castell OIII Deepsky Filter for 2" 2-Inch (31.7 mm) Eyepieces
This OIII filter will allow emission lines of the doubly ionised oxygen (OIII) where most of the light comes from older objects such as planetary nebulae and supernova remnants.
Similarly to the UHC filter, it will also cut off all the light produced by Mercury and Sodium lamps that is important for astronomers in light polluted areas. The result is an astounding visual observation experience: brightness of stars decreased by 2-3 magnitudes, whilst the darker background emphecises the contrast of our main astronomical objects such as nebulae. Details of deep sky objects will plastically stand out from the background, thus producing a photo-like sight of nebulae through larger telescopes (e.g. NGC 6992-6995, Veil Nebula in Cygnus).
This new version comes now in a plastic case.
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