SHO Astronomical Filters
ToupTek Astro SHO Narrowband Filter Set
Hα, SII, and OIII narrowband filter set for monochrome deep-sky imaging workflows
Narrowband filters isolate selected emission lines for monochrome deep-sky imaging and SHO channel capture.
ToupTek Astro SHO narrowband filters are precisely tuned to the three primary ionized emission lines of star-forming regions:
- Hα (656.3nm)
- SII (671.6nm)
- OIII (500.7nm)
These filters reduce out-of-band background light and support SHO channel mapping for emission-nebula imaging.
Technical Parameters
Size Specifications
36mm (unmounted) / 1.25" / 2"
Glass Thickness
2mm
Transmission
>90%
Glass Material
Quartz Glass
Frame Material
Aluminum Alloy
OD Value
≥5.0
Transmission Ranges
SII
Center Wavelength 671.6nm
Hα
Center Wavelength 656.3nm
OIII
Center Wavelength 500.7nm
Full Width at Half Maximum (FWHM)
36mm:
Hα (4nm) / SII (4nm) / OIII (4nm)
1.25" & 2":
Hα (7nm) / SII (7nm) / OIII (7nm)
Surface Treatment: Dual-side high-precision optical polishing
Coating Technology: IAD (Ion Assisted Deposition)
Coating System Design: AR anti-reflection coating + quartz glass + precision cut-off coating layer
Core Features
The narrowband design isolates Hα, SII, and OIII emission lines for SHO channel capture.
SII Filter: Center wavelength 671.6nm, FWHM 4nm.
Supports ionized sulfur channel capture and structural contrast when combined with Hα.
Supports ionized sulfur channel capture and structural contrast when combined with Hα.
Hα Filter: Center wavelength 656.3nm, FWHM 4nm.
Hydrogen-alpha channel for nebula morphology.
Hydrogen-alpha channel for nebula morphology.
OIII Filter: Center wavelength 500.7nm (OIII emission line), FWHM 4nm.
OIII channel for high-energy excitation regions and blue-green emission structures.
OIII channel for high-energy excitation regions and blue-green emission structures.
*1.25-inch and 2-inch filters have FWHM of 7nm.
ToupTek Astro filters use a quartz glass substrate with >90% transmission and blue-violet band transmission for astronomical imaging applications.
The filter coating uses IAD (Ion Assisted Deposition) technology for dense optical coating layers.
The coating stack combines single-side cut-off coating, front-surface AR coating, and edge blackening to reduce internal reflection and stray light.
All channel filters achieve OD≥5.0 cut-off depth to block non-target spectral ranges and reduce channel crosstalk.
Filter edges feature black matte treatment to reduce stray light around the filter edge.
- 36mm filters: Feature recessed black ring facing telescope for quick orientation identification
- 1.25" and 2" filters: Equipped with threaded aluminum frames for direct screw-in installation
All filters feature monolithic, adhesive-free construction.
36mm: Recommended for APS-C and smaller sensor formats
1.25": Recommended for 1-inch and smaller sensor cameras
2": Recommended for full-frame and smaller sensor cameras
Compatible with various brands of 7-position 36mm, 8-position 1.25-inch, and 5-position 2-inch motorized filter wheels.
Spectral Response Curves
Spectral Chart Reading Guide
- Horizontal axis represents wavelength (unit: nm), vertical axis represents transmission (percentage %)
-
Blue line: SII (672.4nm) Red line: Hα (656nm) Green line: OIII (500.7nm)
- Emission nebula signal bands are primarily located at 656nm (Hα), 500.7nm (OIII), and similar wavelengths
- Light pollution peaks typically occur near 540nm and 590nm (sodium/mercury lamp bands)
Astronomical filter transmission regions are designed to avoid these interference bands while preserving the Hα, SII, and OIII transmission ranges.
ToupTek Astro SHO Narrowband Filter Imaging Results
IC5070
Photographer: voice
Telescope: Sky-Watcher
Mount: UMI
Camera: ToupTek Astro ATR2600M
Filters: ToupTek Astro 36mm LRGB&SHO
Exposure: Hα: 30×600s ; SII: 30×600s ; OIII: 30×600s
Total exposure time: 15 hours
IC443
Photographer: voice
Telescope: Sky-Watcher F3.4
Camera: ToupTek Astro ATR2600M / ATR2600C
Mount: UMI
Filters: ToupTek Astro 36mm HSO
Processing: Narrowband composite using HSO channel mapping
Total exposure time: 20 hours
NGC2237
Photographer: 原上行川
Telescope: Askar SQA55
Camera: ToupTek Astro ATR2600M
Mount: iOptron HAE16C
Filters: ToupTek Astro 36mm HSO
Wireless Controller: StellaVita
Exposure: Hα: 71 ; OIII: 63 ; SII: 49
Total exposure time: 15 hours
M16
Photographer: Yahushua
Telescope: Askar 130HNT28-AL
Camera: ToupTek Astro ATR585M
Mount: iOptron CEM26
Guide Camera: G3M2210M
Filters: ToupTek Astro 1.25" HSO
Total exposure time: 7 hours
NGC6357
Photographer: voice
Telescope: Sky-Watcher
Camera: ASI2600M
Filters: ToupTek Astro 2" HSO
Mount: UMi 17
Exposure: Hα: 36×600s ; SII: 36×600s ; OIII: 36×600s
Total exposure time: 18 hours
Installation Guide
36mm Unmounted Filters
During installation, orient the side with the recessed black ring toward the telescope for positioning.
1.25" and 2" Filters
Screw directly into the filter wheel.
Warranty & Service
Quality Assurance Testing
Every filter undergoes spectral testing before shipment to verify optical performance consistency.
Warranty Policy
Two-year warranty covers manufacturing defects. Support is available for setup and usage guidance.
Technical Support
For assistance, please contact our support team:
ToupTek
Astro Technical Support
Important Notes
Color Variations:
Filter coating colors may appear different under various lighting conditions and viewing
angles—this is a normal optical phenomenon.
Product Improvements:
Specifications and appearance may be updated as part of product refinement. Refer to
actual delivered goods.
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