Optolong L-Para Filter 2 inch: dual-band for fast optics from f/2
The L-Para (L-Parallels) is the dual-band filter that Optolong has specially designed for very fast optics. The 10nm passbands around H-alpha (656.3nm) and OIII (500.7nm) maintain a transmission of over 85 percent on the emission lines, even at aperture ratios of f/2 to f/4.
For such fast systems, think of RASA and Hyperstar setups, light falls on the filter at steep angles and narrower filters lose a lot of signal. The L-Para is designed for this and combines that with greatly improved anti-halo properties around bright stars.
Who is L-Para for
Owners of fast astrographs photographing emission nebulae with a color camera. Optolong recommends the filter for skies up to Bortle 7; it also works well on slower telescopes.
Technology
Multi-layer ion-assisted coatings provide a stable central wavelength through temperature fluctuations. The 2 mm thick glass is housed in a thin 2 inch mount with M48 threading.
Featured accessories
A clear focus filter speeds up focusing; we're happy to include one.
For whom yes and for whom no
- ✓ Owners of RASA, Hyperstar, and other f/2 to f/4 systems
- ✓ Belly photographers with color cameras who want halo-free stars
- When looking for maximum contrast with a slow telescope: the L-Ultimate (3 nm) is the better choice
Specifications
| Type | Dual-band notch filter for fast optics |
| Passage | H-alpha 656.3 nm and OIII 500.7 nm |
| Half-value width | 10 nm per band |
| Transmission | More than 85 percent at f/2 and slower |
| Glass thickness | 2 mm |
| Size | 2 inch (M48 x 0.75) |
You can find more accessories for this merk at the Optolong merk page.
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