Baader Planetarium Baader UHC-L / Ultra-L-Booster Filter 65x65mm

The Baader UHC-L filter is specifically designed to combat modern, broad-spectrum LED light pollution, which emits a significant amount of blue light. Older filters were designed for the narrow emission lines of sodium and mercury vapor streetlights and are less effective against the "blueish skyglow" of today's cities.

Use the UHC-L filter as your primary nebula filter for a brighter, more complete view of objects that emit strongly in both Oxygen-III and Hydrogen-Beta, such as the Orion Nebula (M42) or Lagoon Nebula (M8). Switch to a more restrictive OIII filter when you want maximum contrast on objects that are almost pure OIII, like most planetary nebulae.

From a suburban sky, the Baader UHC-L filter will dramatically darken the washed-out background sky, increasing the contrast of the nebula. This will allow you to see fainter outer loops of gas and more intricate detail within the Trapezium region that would otherwise be lost to local light pollution.

While the 65x65mm UHC-L filter's primary application is for imaging with large-format cameras, it can be used visually if you have a compatible filter holder, such as a 2-inch filter slider that accepts unmounted square filters. For standard eyepiece use, a mounted 2-inch round version is more practical.

Yes, the 65x65mm format is ideal for this application. It is large enough to fully illuminate the large sensor in your camera without causing vignetting, even with a fast optical system. The filter will enhance the contrast of the nebula's rich hydrogen-alpha and hydrogen-beta regions against the light-polluted sky.

"Unmounted" means the 65x65mm UHC-L filter is a square piece of optical glass without a threaded metal cell. You must install it into a compatible filter holder, such as a filter wheel or a filter drawer designed for large, square filters, before it can be placed in the optical path.