I bought this opened it used it once then upgraded my camera so not needed having a clear out rrp £289 the original receipt can be provided if wanted less then 2 months old.

The Optolong O-III 3nm Narrowband Filter is engineered to isolate the powerful oxygen-III emission line, making it an exceptional tool for imaging planetary nebulae, supernova remnants, and oxygen-rich deep-sky objects. With an ultra-narrow 3nm bandwidth centred around 500.7nm, the filter delivers maximum contrast while suppressing unwanted light pollution and atmospheric emissions.

By allowing only a very small portion of the spectrum to reach the sensor, the O-III 3nm dramatically improves the visibility of delicate filamentary structures and fine gaseous detail that can be difficult to capture with broader filters. The result is cleaner data, darker backgrounds, and greater separation between the target and surrounding sky.

Optolong has refined the coating process to provide high transmission, excellent wavelength accuracy, and improved control of internal reflections. This helps produce sharper images with reduced background noise and enhanced signal-to-noise performance, even when imaging under challenging sky conditions.

A vital component of any narrowband imaging setup, the Optolong O-III 3nm is an excellent choice for astrophotographers seeking maximum detail and contrast in oxygen-rich celestial targets.

Key Features

Ultra-narrow 3nm bandpass centred on the O-III emission line
Excellent for planetary nebulae and supernova remnants
Suppresses light pollution and atmospheric skyglow
Enhances contrast and fine structural detail
High-transmission optical coatings
Optimised for monochrome CCD and CMOS cameras
Essential for SHO and Hubble Palette imaging workflows
2" Mounted