ZWO narrowband 7 nm HSO fiter set (aka SHO, SKU: ZWO NB7nm1.25)

A set of three narrowband filters with a half width of 7 nm is available. While narrowband filters do not eliminate the impact of light pollution or enhance the brightness of objects, they significantly enhance the contrast between celestial objects and the night sky backdrop in many cases.

The kit comprises three filters: a hydrogen filter (H-alpha band), an oxygen filter (O-III), and a sulfur filter (S-II). These filters enable the observation and, particularly, the capture of color photographs of nebulae, such as emission nebulae, planetary nebulae, and remnants of supernova explosions, even under conditions of intense artificial light pollution. When used together, these three SHO filters create the widely recognized Hubble palette (SHO assignment with respect to RGB channels: sulfur signal - S - corresponds to channel R, hydrogen signal - H - corresponds to channel G, and oxygen - O - is assigned to channel B).

Key features of the filters include:

• FWHM: 7 nm +/- 0.5 nm
• Glass thickness: 2 mm +/- 0.03 mm
• 1/4 λ accuracy for the wavefront
• Transmission: approximately 90% for the 656 nm line (hydrogen filter), approximately 90% for the 672 nm line (sulfur filter), and approximately 90% for the 500 nm line (oxygen filter)
• Transmission <0.1% beyond the pass-through band of the filters
• Infrared cutoff in the range of 700 - 1100 nm
• MC coatings
• Filter holder (length): 5.5 mm + 3.5 mm thread
• Thread: M28.5x0.6
• Size: 1.25" / 31.7 mm