Why is the Baader UV/IR-Cut / L-Filter supplied unmounted?
The filter is unmounted to integrate directly into filter wheels, drawers and carriers made for its size – including the Baader FCCT (Filter Changer & Camera Tilter) for the 47.4 mm version. This design minimizes the consumption of precious back focus, reduces potential vignetting, and ensures a rigid, stable optical path without the added length and mechanical complexity of a standard threaded filter cell.
What does "CMOS-optimized" mean for this UV/IR-Cut filter?
CMOS-optimized means the filter features advanced anti-reflection coatings designed to prevent halos and other artifacts caused by reflections between the filter and the highly reflective surface of a CMOS sensor. This is especially important for maintaining clean, high-contrast images of fields containing bright stars.
Which size do I need, and will it fit a standard 2" filter wheel?
All versions are unmounted, so none will fit a standard filter wheel drawer or carousel designed for threaded M48 (2") mounted filters. Choose the size your holder accepts: 31 mm or 36 mm round for wheels made for those diameters, 50.4 mm round or 50x50 mm / 65x65 mm square for large filter wheels and drawers used with full-frame or larger sensors, and 47.4 mm exclusively for the Baader FCCT system.
If I'm imaging the Pleiades (M45) with a refractor, how does this L-filter help?
When imaging a reflection nebula like the Pleiades (M45), the bright blue stars are strong sources of UV and IR light. This filter blocks that out-of-band light, which refractors cannot bring to the same focal point as visible light. The result is significantly tighter stars, sharper detail in the faint nebulosity, and the prevention of "blue bloat" that can overwhelm the image.
How does this filter benefit imaging the Andromeda Galaxy (M31) with an SCT?
For a broadband target like the Andromeda Galaxy (M31), this filter serves as your high-transmission luminance channel. Its strict UV/IR blocking is critical for SCTs, which often use corrector plates that are not optimized for these wavelengths. By isolating the visible spectrum, you achieve a much sharper luminance frame with better contrast between the galaxy's core, dust lanes, and faint outer arms.
Is this filter only for monochrome cameras?
It is designed primarily as a luminance (L) filter for monochrome LRGB imaging. It can also help a color CMOS camera that lacks a sufficient built-in IR-cut filter, where the missing IR blocking leads to a reddish cast and bloated stars. If your color camera already has a UV/IR-cut window in front of the sensor, adding this filter usually brings little additional benefit.