Filter Astronomik O-III in the frame 1.25 "/ 31.7 mm.
The primary purpose of the O-III filter are visual observations of gas and planetary nebulae. The very narrow band transmitting two lines of double ionized oxygen (O-III) introduces a significant increase in the contrast of these lines, even under the best observational conditions. In the case of faint supernova remnants and planetary nebulae, the use of the O-III filter is often decisive if we see the object or not.
The filter has been optimized for light between 1: 3 and 1:15 and the aperture (active diameter) at least 150 mm. Transmission drops and distortions associated with chromatic aberration can only be manifested in extremely bright systems with a light intensity greater than 1: 3. The Astronomik OIII filter works very well in the whole field of view - not only in the middle of the field. Thanks to the high quality of workmanship, the stars visible through the filter will be like heels - just like watching the telescope without the use of a filter (no halo / flare, etc.).
The O-III Astronomik filter passes such a narrow bandwidth that its use with telescopes smaller than 150 mm is not recommended - smaller telescopes collect too little light to ensure satisfactory effects on weak astronomical objects. For apertures over 10 inches (250 mm), many advanced observers prefer the OIII filter more than the more-permeable UHC filter.
• visual observations under the dark sky: a very good, great improvement in the contrast of the nebulae emitting in the O-III band
• visual observations under the urban sky: a very good, great improvement in the contrast of the nebulae emitting in the O-III band
• photography on film: variously; very long exposure time required
• CCD photography: good when used with an additional IR filter
• unmodified mirror photography: a very good, great improvement in the contrast of the nebulae emitting in the O-III band
• photo of a reflex camera modified for astrophotography: very good, great improvement of the contrast of nebulae emitting in the O-III band
• webcam / video cameras for planetary photography: not applicable
• webcam / video cameras for photographing nebular objects: reasonable, when light pollution is a big problem, and the emitting objects in the OIII band are observed
• transmission close to 100% for both O-III lines (496 and 501 nm)
• complete blocking of disturbing wave lengths
• the filter works perfectly with telescopes with a diameter of 10 "/ 25 cm and larger
• diffraction-limited accuracy
• parchocal with other Astronomic filters
• thickness: 1 mm
• resistant to moisture, scratch, does not age
Connection of ALL astronomical filters with the exception of solar film filters (which are filters for the lens) is accomplished by screwing the filter into the frame of the eyepiece from the opposite side than applying the eye (ie from the side that we put in the eyepiece extractor) . The filters can be additionally connected with each other, because they have threads on both sides of the luminaire.