Baader 3.5/4nm f/2 Ultra-Highspeed SII Filter - 65x65mm Square Unmounted
Baader Planetarium
Baader 3.5 / 4nm f/2 Ultra-Highspeed Filters – CMOS-optimized (H-alpha / O-III / S-II) - SII / 65 x 65mm is a narrowband filter in 65 x 65mm for mono emission-line imaging.
Best Current Offer
Specifications
Filter
- Filter type
- Single-line narrowband filter
- Filter size
- 65 x 65 mm
Spectral
- Passbands
- SII 672.4 nm (4 nm)
- Band count
- 1 band
- Narrowest bandpass
- 4 nm
Use
- Camera use
- Mono astronomy cameras
- Fast optics note
- Fast-optics optimized
Astrophotography Fit
Best for isolating emission lines with a mono camera and filter wheel.
Baader 3.5 / 4nm f/2 Ultra-Highspeed Filters – CMOS-optimized (H-alpha / O-III / S-II) - SII / 65 x 65mm is a midrange narrowband filter (65 x 65mm).
Best for isolating emission lines with a mono camera and filter wheel.
Choose filter size around the sensor diagonal, telescope speed, and filter-wheel or drawer geometry. Flats are still required; a filter can improve contrast, but it will not rescue tilt, bad focus, or poor calibration.
Best paired with
- Monochrome camera, matching filter wheel, and autofocus offsets
- Ha/OIII/SII emission nebula projects
- Long integrations with darks, flats, and careful star handling
Not recommended for
- Unmodified color cameras as the primary workflow
- Targets dominated by broadband continuum signal
- Slower systems if the filter is a highspeed/f/2-shifted version
Where To Buy
Some links on this page are affiliate links. Prices and availability are pulled automatically from each retailer and updated daily.
| Retailer | Price | Availability | View Offer |
|---|---|---|---|
| Starizona Starizona | $671.00 | In stock Updated 8/5/2026 | View Offer - $671.00 |
Price History
Chronological retailer pricing with out-of-stock points shown at reduced opacity.