Optolong L-Ultimate Filter 3nm 2 inch

Optolong Filters L-Ultimate 2″ is the flagship among Optolong's dual-band narrowband filters. Designed for astrophotography with color cameras (One-Shot-Color CMOS and DSLR), this filter allows only the emission lines H-alpha (656 nm) and OIII (500 nm) to pass through. With an extremely narrow passband of only 3 nm per line, the L-Ultimate blocks virtually all unwanted wavelengths, including interfering artificial light and moonlight.

The result is unparalleled contrast and detail in emission nebulae such as the Veil Nebula, the North American Nebula or the Orion Nebula. Even in heavily light-polluted urban areas, structures remain visible that can normally only be photographed under dark sky conditions. The narrow transmission peaks also make the filter ideal for long exposure times and stacking, where subtle nebular detailing comes to the fore.

The L-Ultimate differs from wider dual-band filters such as the L-eNhance and L-eXtreme by having an even narrower bandwidth, resulting in a higher signal-to-noise ratio. This makes the filter particularly popular among advanced astrophotographers who want to get the most out of their camera and optics. The filter is made of high-quality optical glass with multiple anti-reflection coatings and mounted in a rugged 2″ aluminum mount, suitable for use in filter wheels and 2″ adapters.

Observation goals
This filter is ideal for serious astrophotographers who photograph emission nebulae with an OSC camera or DSLR, and who still want to capture top-quality images under heavy light pollution or during moonlight. Not suitable for visual use, as the extremely narrow bandwidth allows too little light to pass through for the human eye.

Specifications

• Type: Dual-band ultra narrowband filter
• Diameter: 2″ mount
• Transmittance: H-alpha (656 nm, 3 nm) and OIII (500 nm, 3 nm)
• Material: Optical glass with multiple anti-reflection coating
• Mount: Aluminum
• Application:
  • ✓ Emission nebulae in highly light-polluted areas
  • ✓ Astrophotography with OSC and DSLR cameras
  • ✓ Long exposure times and stacking
  • ✗ Not suitable for visual use