Astronomik L-1 - UV IR Block Filter 31 mm, unmounted, with protective ring

Astronomik Luminance L-1, L-2, L-3 Filters

The luminance channel is most important for a perfect astrophoto! Sharpness, contrast and low noise of the luminance data are crucial to achieve the best possible quality in the final result.

Astronomik offers three UV+IR block filters for the luminance channel. The passbands are chosen in a way that an optimal sharp and high contrast image can be obtained with all optics and any CCD and CMOS camera.

The task of the L-filter is to have the maximum transmission over the complete visible spectrum, because the combination of the widest possible passband and high transmission makes it possible to capture the largest possible number of photons.

In the "real" world, unfortunately, not all telescopes or auxiliary elements such as correctors, field flatteners, or Shapley lenses have perfect color correction. An L-filter that is too broadband will pass wavelengths for which an optic may not be fully corrected. The result is unsightly bloated, out-of-focus stars that do not match the RGB color channels.

The Astronomik L-1, L-2, and L-3 filters eliminate or reduce the problem.

Selecting the correct filter

Depending on the color correction of the instruments used, the L filter with the largest useful passband should be used. The L-1 filter has by far the largest spectral passband, whereas the L-3 filter has the narrowest spectral window. The L-2 filter is equivalent to a "normal" L filter.

If your used optics can be classified as "color error free", the L-1 filter is the right choice. For general use, e.g. on telescopes of different color acuracy or the use of additional refractive elements in the light path, we recommend the Astronomik L-2 version. For "colorful" optics, we recommend the Astronomik L-3 filter to increase image sharpness.

The transmission properties and coating technology of the Astronomik L-series have been developed to suppress halos or reflections in the best possible way. Even with bright stars in the field of view, nebulae and galaxies are imaged with finest structures and highest contrast.

Like all filters from Astronomik, the L-1, L-2 and L-3 filters have an extremely robust and durable coating, applied to a fine-optical special substrate, as it 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 operation: Perfect homofocality and lowest wedge error are the resulting advantages.

A supplement for photographers working under light-polluted skies:

Use the Astronomik CLS CCD filter instead of a luminance filter! You´ll get an L signal without the lines of sodium and mercury vapor lamps, with much less background noise. Feedback from highly satisfied customers from all over the world confirms the advantages of the CLS-CCD filter for the luminance channel and makes color photography of the deep sky possible in some regions in the first place!

♦ 1 Filter in a robust plastic box