ZWO 31mm Ha 7nm Unmounted Narrowband Filter

ZWO 31mm Ha 7nm Unmounted Narrowband Filter

  (3 Reviews)
✓ 2 year warranty


1x in stock shipped 1-2 working days

About this product

Model:  zwo_ha_31-7nm
Part Number:  ZWO-Ha7nmD31

New & Improved with higher light transmission and less reflection (reduced halos around bright stars). 

The ZWO H-Alpha filter has a bandpass of  7nm and passes light at 656nm wavelength. Light transmission peaks at around 90%. 

Providers high-contrast images with rich detail of nebula, even in areas with strong light pollution! 


  • FWHM: 7±0.5nm
  • Glass Thickness 2.0+/-0.03 mm (1.25”/31mm/36mm)
  • Fine optically polished glass ensures accurate 1/4 wavefront over both surfaces
  • Around 90% transmission at H-alpha line 656nm
  • Infrared wavelength 700-1100nm cut-off
  • <0.1% transmission of off-band, OD3 (Optical Density)

Transmission Curve

Customer reviews

Average Rating (3 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
1st NB filter
19 February 2023  | 

Havenít had much sky time yet but looking good so far. Top tip : educate yourself on figuring out which side faces the camera - the pen reflection technique (google it) worked for me but involved a flip over on the filter wheel as I put it in the wrong way round initially.

Rating (max 5):  
Fast delivery and good results so far
30 April 2021  | 

Delivered the next day which was great. Have used this filter in a ZWO EFW only twice with asi1600mm but results were great. Definately no halos seen yet although there's very slight vignetting but nothing that cant be resolved in post processing.

Rating (max 5):  
Works as it should and seems par-focal with my other ZWO filters.
18 February 2019  | 

Great for picking out nebula in galaxies. The cone nebula looked well defined, when nothing was showing in R,G, or B.( bright moon)


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