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Available in 1.25" & 2"

The Optolong L-eXtreme filter is a light pollution dual band filter designed to drastically reduce the effect of light pollution. Its two passing bands isolate the nebulae emissions in H-Alpha (red) and OIII (green-blue).

The advantage of the L-eXtreme filter is that there is no transmission between the H-Alpha and OIII lines as there are no nebula emission lines there. It blocks the light pollution, maximises nebulae signal and makes the sky background dark.

The L-eXtreme filter works well under bright urban skies. Different from the Optolong L-eNhance filter which is a tri-band (transmits H-beta, H-Alpha, and OIII), the L-eXtreme filter is dual band to reduce the effect of light pollution even more.

NOTE: It is not recommended to use the L-eXtreme with telescopes faster than f/4 as the H-Alpha transmission decreases significantly. Instead, we recommend the L-eNhance filter.

This filter is designed for DSLR's and colour cameras used under urban skies. It works as a combined H-Alpha and OIII narrowband filter so photos will appear highly contrasted without the necessity to use a monochrome camera and two separate filters.​​

Spectrum Optolong L-eXtreme.png

High transmission

7nm bandpass at OIII (496nm & 500nm) and H-alpha (656nm) emission lines, with 90% transmission.

Blocks artificial light

Cuts through mercury vapour, high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere.

Built-in UV/IR cut

No need to use a separate UV/IR cut filter with cameras sensitive to infrared radiation.

Schott optical glass

2mm thick glass made of Schott monolithic optical substrate (non-glued), in ultra-thin, CNC-machined, anodized filter cell.

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