ZWO H-Alpha 7nm CCD Filter
Best specialized filter for capturing detailed nebulae.
This specialized astronomical filter is designed to capture the H-Alpha emission line, crucial for observing nebulae and other deep-sky objects. Its 7nm bandwidth provides exceptional detail by isolating specific wavelengths of light, reducing interference from light pollution and other celestial sources. The 2-inch format ensures compatibility with a wide range of astronomical cameras and telescopes, making it a valuable tool for astrophotographers seeking to enhance their images with vibrant hydrogen-alpha data. It effectively isolates the red light emitted by hydrogen atoms, revealing intricate structures in nebulae that might otherwise be obscured.
$299.00
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ZWO 31mm H-alpha Filter - 7nm
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Owner Satisfaction
4.7
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Category Rank
607
/ 2593
#607 in Telescope Accessories
Price vs Category Average
-55%
Below average
Filter Type
H-Alpha
/ H-Alpha
Who it's for
- Astrophotographers capturing faint nebulae from bright urban skies.
- Urban imagers seeking to overcome city light interference.
- Serious imagers prioritizing pristine data for detailed nebulae.
Who should skip it
- Newcomers expecting vibrant, full-color images from a single filter.
- Imagers with limited time or patience for very long sessions.
- Enthusiasts needing a versatile filter for various celestial objects.
Performance breakdown
Light Pollution Suppression
Narrow 7nm bandwidth effectively blocks unwanted city glow for clearer captures.
Nebula Contrast
Isolates hydrogen-alpha emissions to reveal hidden structural details in deep-sky objects.
Transmission Efficiency
High 90% transmission at 656nm ensures maximum signal capture for faint targets.
Build Compatibility
Standard 2-inch format integrates seamlessly with most common astrophotography camera setups.
Out-of-Band Rejection
Minimal off-band transmission prevents unwanted light leakage from polluting your final image.
Optical Precision
Consistent 7nm FWHM provides reliable performance across the entire sensor field.
Key Specs
Filter Type
H-Alpha
Bandwidth
7nm
Format
2 Inch
Thickness
5mm plus 2.5mm thread
Glass thickness
1.85mm
Thread
M48x0.75 male
FWHM
7nm
Transmission at 656nm
90%
Know before you buy
A 7nm bandwidth is narrow enough to isolate the specific light emitted by hydrogen atoms while blocking most other wavelengths. This significantly increases the contrast of nebulae and allows you to capture high-detail images even when shooting from light-polluted areas.
This filter features a standard M48x0.75 male thread, which is compatible with most 2-inch filter wheels, filter drawers, and eyepiece holders. Ensure your specific camera or imaging train supports 2-inch threaded accessories before purchasing.
While it is technically possible to use this for visual observation, it is designed primarily for astrophotography. Because the filter is so narrow, the image will appear very dim to the human eye, making it difficult to see anything other than the brightest emission nebulae.
The filter includes a built-in infrared cut-off that blocks wavelengths between 700nm and 1100nm. This prevents infrared light from reaching your sensor, which helps maintain sharp focus and prevents bloated stars in your final images.
You can use this filter on its own to create monochrome H-Alpha images, which are excellent for highlighting structural details in nebulae. If you want to create a full-color image, you would typically combine this data with images taken through Oxygen-III and Sulfur-II filters to create a 'Hubble Palette' or SHO image.
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