Optolong Clear Focusing Filter 1.25 inch: focus first, then narrowband
Focusing through a narrowband filter is tricky: the image is dark and stars are barely visible. This bright filter solves that. With 98.5 percent transmission between 420 and 680 nm, you can focus quickly and accurately, and then switch to your narrowband filter for the shot.
Furthermore, this is the ideal filler for the empty position in a filter wheel: it keeps the optical path length the same as your other filters and protects the sensor from dust.
Features
- 98.5% transmission between 420 and 680 nm
- Maintain focus consistent with filled filter wheel positions
- Acts as a dust cap and protective filter for the sensor
- Thin 1.25 inch metal barrel
Compatibility
Fits the standard 1.25 inch thread (M28.5 x 0.6) in filter wheels, nosepieces, and filter holders.
Specifications
| Type | Bright focus filter |
| Transmission | 98.5 percent (420 to 680 nm) |
| Size | 1.25 inches (M28.5 x 0.6) |
| Observation goals | Focusing, filter wheel filling, sensor protection |
You can find more accessories for this brand at the Optolong brand page.
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