Optolong Filters SHO 6,5-7nm 36mm (87509)

Optolong Filters SHO 6.5–7 nm 36 mm (Model 87509)

The Optolong SHO 6.5–7 nm filter set is a versatile narrowband solution designed for astrophotographers who want high contrast and improved performance under light-polluted or moonlit skies. This three-filter set includes H-alpha, OIII, and SII filters, each optimized to isolate key emission lines from nebulae. By transmitting only specific wavelengths and blocking unwanted light, these filters significantly enhance detail and background darkness. They are ideal for long-exposure imaging and allow productive observation even when the Moon is visible.

Narrowband filters improve image contrast by allowing only selected spectral lines to pass through, such as hydrogen (H-alpha at 656 nm), oxygen (OIII at approximately 500 nm), and sulfur (SII at 672 nm). Artificial lighting and natural skyglow are largely suppressed, making them particularly effective for urban astrophotography.

OIII Filter
The OIII filter isolates the oxygen emission line around 500 nm with a narrow bandpass in the 6.5–7 nm range. It enhances contrast in planetary nebulae and supernova remnants by blocking nearly all other wavelengths.

H-alpha Filter
The H-alpha filter transmits light at 656 nm within a 6.5–7 nm bandwidth. It is one of the most important filters for nebula photography, revealing fine structural details and maintaining strong contrast even in light-polluted environments.

SII Filter
The SII filter isolates sulfur emission at 672 nm with a similar narrow bandpass. It is designed for imaging emission nebulae and is essential for creating tri-color narrowband images in the classic SHO (Hubble palette) style.

When combined, the H-alpha, OIII, and SII filters allow astrophotographers to produce detailed tri-color compositions similar to those associated with space telescope imagery. This technique works effectively even during bright lunar phases, ensuring that imaging equipment can be used throughout the month.

Mechanical and Optical Specifications
Filter size: 36 mm
Mount type: Unmounted
Optical coating: Multi-layer, plane-parallel
Bandwidth (FWHM): 6.5–7 nm
Filter thickness: 2 mm
Number of filters included: 3

Type and Application
Type: Line filters (SHO set)
Suitable for astrophotography: Yes
Visually useful: Yes
Anti light-pollution capability: Yes
Suitable for nebulae and galaxies: Yes
Suitable for planetary nebulae: Yes
Suitable for supernova remnants: Yes
Suitable for hydrogen nebulae: Yes