The Antlia OIII Pro 3 nm filter is designed for photographing deep-sky objects that emit light in the OIII line of doubly ionized oxygen. Its 3 nm bandwidth is centered at 500.7 nm. It selects this emission while reducing unwanted background sky light, in order to better highlight the structures of nebulae.
Price range: CHF 218.79 through CHF 643.50
The Antlia OIII Pro 3 nm filter is designed for photographing deep-sky objects that emit light in the OIII line of doubly ionized oxygen. Its 3 nm bandwidth is centered at 500.7 nm. It selects this emission while reducing unwanted background sky light, in order to better highlight the structures of nebulae.
Antlia offers a peak transmission greater than 88 % and out-of-band blocking greater than OD5 in the 300–1000 nm range. The spectral profile with a pronounced cutoff is also designed to minimize halos around bright stars. This narrow band is useful for emission nebulae, planetary nebulae, nebulae associated with Wolf-Rayet stars, and supernova remnants that exhibit OIII emission. It does not make this filter a one-size-fits-all solution for all deep-sky objects.
The manufacturer describes its use in both light-polluted skies and dark locations. Filtering can also extend imaging capabilities when the Moon is visible. Antlia states that the Pro series can operate up to f/3 with minimal signal loss. When choosing between the standard Pro version and the Highspeed version, however, it is important to consider the instrument’s focal ratio and the specific recommendations for each of these product lines.
This data sheet lists the 1.25″ and 2″ mounted sizes, as well as the 31, 36, and 50 mm unmounted discs and the 50 × 50 mm unmounted square. The mounted versions use M28.5 × 0.6 and M48 × 0.75 threads, respectively. The unmounted versions require a housing adapted to their dimensions. The glass thickness is 2 mm ± 0.05 mm for both mounted sizes and for the 31- and 36-mm discs; it is 3 mm ± 0.05 mm for the 50-mm and 50 × 50-mm sizes.
The filter uses a unique, non-adhesive optical substrate. The edges of the unmounted versions are blackened to minimize stray reflections. The mounted versions feature a slim cell with a black anodized finish and laser engraving. This filter is intended for imaging: Antlia does not recommend it for nighttime visual observation or solar imaging. Never look at the Sun through this filter, as it does not provide solar protection for the eyes.
| Stingray | OIII |
|---|---|
| Center wavelength | 500.7 nm |
| Bandwidth FWHM | 3 nm |
| Peak Transmission | > 88 % |
| Out-of-band blocking | > OD5, 300 to 1,000 nm |
| Substrate | Optical, single-piece, and unglued |
| Formats | 1.25″ and 2″ (mounted); 31, 36, 50, and 50 × 50 mm (unmounted) |
