The Antlia ALP-T 5 nm H-alpha/OIII Highspeed filter simultaneously selects the red H-alpha emission from hydrogen and the blue-green OIII emission from oxygen. It is primarily intended for color cameras used to photograph emission nebulae, whether they are SLR cameras or astronomical cameras with CMOS or CCD sensors. Both useful bands are recorded during the same exposure.
Price range: CHF 275.35 through CHF 351.12
The Antlia ALP-T 5 nm H-alpha/OIII Highspeed filter simultaneously selects the red H-alpha emission from hydrogen and the blue-green OIII emission from oxygen. It is primarily intended for color cameras used to photograph emission nebulae, whether they are SLR cameras or astronomical cameras with CMOS or CCD sensors. Both useful bands are recorded during the same exposure.
The Highspeed version uses offset bands centered at 657.8 nm for H-alpha and 502.2 nm for OIII. Antlia recommends it specifically for focal ratios ranging from f/2.2 to f/3.6. For focal ratios higher than f/3.6, the manufacturer recommends the standard version. With optics faster than f/2, the simulation cited by Antlia indicates a possible decrease in transmission of 15 to 20 % at the emission lines: the compensation therefore does not eliminate all losses.
The multilayer coating reduces the transmission of unwanted wavelengths associated with light pollution, moonlight, and sky glow. The stated blocking performance is at least OD4.5 over the 300–1050 nm range. The spectral profile, with a flat peak and steep edges, is designed to preserve the useful signal and limit internal reflections. The substrate is polished on both sides and then coated with optical layers using ion beam deposition.
The 2″ size comes in an M48 × 0.75 threaded mount. The second option is the 36 mm filter (unmounted) accompanied by a B-4836 adapter. The manufacturer’s size and price chart specifies that a B-4836 adapter is included with this 36 mm offering, for both the standard and Highspeed versions. This adapter allows the unmounted disc to be fitted into a 2″ filter slot. The glass has a thickness of 2 mm ± 0.05 mm in both sizes.
Although this series is primarily designed for color cameras, Antlia also mentions its use with monochrome cameras to record both bands simultaneously. The filter is intended for photographing nebulae and is not a substitute for solar safety equipment. The manufacturer advises against nighttime visual observation and solar imaging. Never look at the Sun through this filter: the selection of certain spectral bands does not protect the eyes from solar radiation.
| Strips | H-alpha and OIII |
|---|---|
| FWHM | 5 nm per band |
| Central Wavelengths | 657.8 and 502.2 nm |
| Blocking | ≥ OD 4.5, 300 to 1050 nm |
| Thickness | 2 mm ± 0.05 mm |
| Formats | 2″ mounted; 36 mm unmounted with B-4836 bracket |
