The luminance channel is very important for a successful astrophoto! Sharpness, contrast and low noise of the luminance data are decisive for achieving the best possible quality in the final result!

The task of the L filter is to maximise transmission over the entire visible spectrum, because the combination of the widest possible aperture and high transmission makes it possible to capture the greatest possible number of photons.

Not all telescopes or additional elements such as correctors, field flatteners and Shapley lenses have perfect colour correction. An L filter that is too broadband allows wavelengths to pass for which your optics are not properly corrected. The result is unsightly, blurred stars that do not match the RGB colour channels.

Astronomik presents three different UV+IR block filters for the luminance channel, labelled L-1, L-2 and L-3. Please pay attention to the corresponding designation in the product name.

How to find the right luminance filter: Depending on the colour correction of the instruments used, the L filter with the largest aperture should be used. The L-1 filter has by far the largest spectral aperture, whereas the L-3 filter has the narrowest spectral window. If the optics you are using can be classified as free of colour errors, the L-1 filter is the right choice. For general use, e.g. on telescopes of different colour purity or when using additional refractive elements in the light path, we recommend the Astronomik L-2 version. For ‘colourful’ optics, e.g. an achromat, we recommend the Astronomik L-3 filter to increase the sharpness of the image.

The transmission properties and coating technology of the new Astronomik L series have been developed in such a way that no halos or reflections are visible. Even with bright stars in the field of view, nebulae and galaxies are imaged with the finest structures and maximum contrast.

Like all filters from Astronomik, the L-1, L-2 and L-3 filters have an extremely resistant and durable coating, applied to a special fine-optical substrate that is also used in space travel. The basic requirement for such material is freedom from streaks, stresses and bubbles. Furthermore, the Astronomik filter substrates are processed to the same thickness in a separate work step: Perfect homofocality and minimal wedge error are the resulting advantages!

Tip: Use the Astronomik CLS filter instead of a luminance filter! You get an L-signal without the lines of sodium and mercury lamps with much less background noise.

Scope of delivery:

• Filter 36mm with ring mount