The Optolong LRGB 2″ filters are specially designed for deep space photography with monochrome cameras. The strict manufacturing process and the quality control guarantees a tight tolerance of the filter thickness (± 0.05mm) which makes these filters parfocal. This allows the filter change without the need to refocus.

Each filter is fully multi-coated to minimise internal reflections, halos around stars and to assure a high transmission which is above 95%.

Each filter cuts off the ultraviolet and infrared light so there is no need to use the L filter in combination with the colour filters.

The width of bandpass of the 3 RGB filters is balanced with the spectral response of the most common CCD and CMOS cameras. This expedient allows to balance the exposure of each channel with the ratio of 1:1:1. That means the exposure time in red is equal to the exposure time in green and in blue. During post-processing, it will be easier to obtain images with a natural colour balance thus without colour dominances. The fourth L filter assures a transmission above 95% across the visible spectrum (400nm to 700nm) cutting out ultraviolet and infrared light.

The design of these filters is optimised to cut out the typical yellow emission of the sodium and mercury lamps around 589nm.

Specifications: