O-III filter has been very specifically designed for the visual observation of gaseous and planetary nebulae. The extremely narrow pass band of the two OIII lines brings a substantial contrast gain to these lines even under best observation conditions. On faint super nova remnants and faint planetary nebulae the OIII filter will often make the difference as to whether the object can bee seen or not!
Main use
Since enough light must be available to make use of the OIII filter it is best to use this filter with apertures of more than 6" (150mm). Smaller instruments do not gather enough light for meaningful and satisfying astronomical work. However, please note: Many experienced Deep Sky observers, with apertures of more than 10" (250mm), prefer using the OIII filter instead of the more versatile UHC filter. Due to the high optical quality of the OIII filter substrate you will see the same needle-sharp stars as you would from your regular telescope.
Suitability
 
Visual observation (dark skies): Verry good, huge contrast enhancement at O III-emission nebulas
Visual observation (urban skies): Verry good, huge contrast enhancement at O III-emission nebulas
Film photography: It depends, very long exposure time
DSLR photography (original): Verry good, huge contrast enhancement at O III-emission nebulas
DSLR photography (astro modified): Verry good, huge contrast enhancement at O III-emission nebulas
DSLR photography (MC modified): Good, when used with an additional IR-block-filter
Webcam / Video (Planets): Unsuitable
Webcam / Video (Deep Sky): Reasonable, if light pollution is a big problem and OIII Objects are beeing observed
Technical Data
 
Transmission of nearly 100% of both OIII lines
Complete blocking of all disturbing wavelength coverages
The ideal filter for telescopes 10 " (25cm) and larger
Main operational use: Planetary nebulas & super nova remnants
No moisture-sensitivity, no aging, and totally scratch-proof
Excellent carrier material - substrate is optically polished. The optical performance (resolution & contrast) of your telescope is not reduced in any way by the filter.
Parfocal with other Astronomik filters
Glass thickness: 1mm
Completely resistant against high humidity, scratches and aging effects
Diffraction limited, the filter will not reduce the optical performance of your telescope!
Astronomik filters are delivered in a high-quality, long lasting, filter box