Optolong L-Ultimate 3 nm Dual Band Filter, 2"

Optolong L-Ultimate 3 nm Dual Band Filter, 2"

The Optolong L-Ultimate filter is a light pollution dual band filter designed to drastically reduce the effect of light pollution. Its two ultra-narrow 3 nm passing bands isolate the nebulae emissions in H-alpha (red) and [O III] (green-blue).

It blocks the light pollution, maximises nebulae signal and makes the sky background dark. The L-Ultimate filter is designed for astrophotography under urban skies.

Astrophotographic results obtained with this filter on Astrobin

Here you can find some astrophotographs made with this filter: Link to Astrobin

Properties

It blocks the artificial light from mercury vapour lamps, both high and low pressure sodium vapour lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (skyglow).

Maximum transmission of the main nebula emission lines at [O III] (496 nm and 500 nm) and H-alpha (656 nm)

Two transmission bands with a bandpass of 3 nm

Designed mainly for astrophotography with color cameras

Also helpful with monochrome cameras, no need to change filters for catching both lines

Ideal for urban areas with extreme light pollution

For little light pollution or using monochrome cameras, other filters can be suited better.

It incorporates an IR/UV cut filter that is necessary in astrophotography, especially for astronomy cameras that are sensitive to the infrared radiation.

Ultra-thin filter cell to maximise the compatibility with most filter wheels.

Multi-layers anti-reflection coating

No obvious halo around bright stars

Cell in aerometal material, CNC machined, sand blasted, black anodized and laser engraved

PP plastic case, high pressure EVA case lining

Light pollution filters do not eliminate the effects of light pollution or increase the object’s brightness. It does increase the contrast between nebulae and night sky.

The interferential coating is deposited on the substrate using electron-beam gun evaporation with Ion-assisted deposition coating technology. This increases the filter durability and resistance to scratching, as well as stability on CWL (central wavelength) and no deviation affected by temperature changes. The planetary rotation system offers precision and homogeneity of coatings ensuring high transmission of pass-band and high optical density off-band.

Which side of the filter needs to face towards the telescope?

Optolong has a good explanation on their page with a check on unmounted filters. With mounted filters, it´s easy. The side with the external thread must face the camera.

Link to iOptron page: Should Optolong filters be installed in a certain orientation? (external link)
You can download the generated PDF from our own server.