ToupTek Astro PureSight A1 Dual Narrowband Filter Introduction
ToupTek Astro PureSight A1 Hα & OIII Dual Narrowband Filter is designed for deep-sky astrophotography under light-polluted skies. With a precise 5nm bandpass and optimization for fast optical systems, it enhances nebula contrast while effectively suppressing unwanted background light.
User Gallery
SH2-308 (Bortle 4.9)
Rosette Nebula (Full Moon)
What is a Dual Narrowband Filter?
A dual narrowband filter is an astrophotography filter designed to isolate specific emission wavelengths, typically hydrogen-alpha (Hα) and oxygen III (OIII). By transmitting only these narrow spectral bands, the filter significantly enhances the visibility of emission nebulae while suppressing background light pollution.
Dual narrowband filters are widely used for deep-sky astrophotography, especially when imaging nebulae from urban or suburban locations where sky brightness can reduce contrast.
High-Performance Dual Narrowband Filter for Fast Optical Systems
ToupTek Astro PureSight A1 Hα & OIII Dual Narrowband 5nm F/3.2 Astronomical Filter is engineered specifically for astrophotography with fast optical systems.
With precisely controlled 5nm FWHM bandpasses and center wavelengths optimized for fast optics, the filter delivers excellent performance on systems from F/3.2 and faster, achieving an ideal balance between strong light-pollution suppression and high signal transmission.
Advanced anti-reflection coatings and carefully controlled surface precision significantly reduce internal reflections, effectively suppressing halos and ghosting. The result is clean backgrounds, high contrast, and sharp stars, even when imaging from urban or suburban locations.
Technical Parameters
| Product Name | PureSight A1 Hα & [OIII] Dual Narrowband 5nm F/3.2 |
| Target Emission Lines | Hα 656.3nm & [OIII] 500.7nm |
| FWHM | 5.0nm ± 1.2 / 5.0nm ± 1 |
| Transmission Rate | ≥90% |
| OD | ≥5 @ 200-1100nm |
| Substrate | Fused Silica |
| Thickness | 2.00mm ± 0.1 |
| Parallelism | ≤ 30" |
| Surface Quality | 60/40 |
| Recommended F-ratio | ≥ F/3.2 |
| Coating | IAD (Ion Deposition) |
| Size | 2-inch (frame height: 5mm, thread height: 2mm) |
| Thread | M48×0.75 |
| Frame Material | Aluminum Alloy |
| Clear Aperture | 43.9mm |
| Installation Direction | Threaded side toward the sensor |
Transmission Spectrum
ToupTek Astro PureSight A1 5nm Hα & [OIII] Dual Narrowband Filter features high transmission in both the Hα and [OIII] emission bands, while deeply blocking common light-pollution wavelengths. From fast optical systems to standard focal ratios, it extracts clean, high signal-to-noise nebular data for astrophotography.
Key Features
Reduce Light Pollution with Precise Narrowband Control
Astrophotographers often face challenges when imaging from urban or suburban locations where artificial lighting reduces contrast and washes out faint nebula structures.
The ToupTek Astro PureSight A1 dual narrowband filter features a 5nm ultra-narrow FWHM bandpass precisely tuned to isolate Hα (656.3nm) and [OIII] (500.7nm) emission lines. This allows key nebula signals to pass through while effectively blocking most sources of artificial light pollution.
With a blocking depth of OD ≥5 (0.001% transmission), the filter suppresses over 99.999% of unwanted light, including streetlights, neon lighting, and urban skyglow.
Ideal for Emission Nebula Imaging
Dual narrowband filters are particularly effective when capturing emission nebulae that radiate strongly in Hα and OIII wavelengths.
When paired with a monochrome or color astronomy camera, the filter enhances faint nebula structures while maintaining natural star colors.
High Compatibility
Standard M48×0.75 thread, compatible with filter wheels and filter drawers. The 2-inch format is suitable for full-frame and smaller color astronomy cameras.
Exceptional Image Purity
Halo-free performance with premium optical materials
Capture faint nebula details even from urban balconies or city skies.
Installation
ToupTek Astro PureSight A1 5nm Hα & [OIII] Dual Narrowband Filter features a specialized coating process that eliminates the need to identify front or back—simply screw it in for quick and easy installation.
The filter comes standard with a 2-inch housing and M48×0.75 thread, ensuring direct compatibility with most astrophotography accessories. During installation, please ensure that the threaded side faces the camera sensor.
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