This filter was designed to transmit the maximum amount of incoming light, while suppressing skyglow due to artificial lighting and background glow when the Moon is up. The filter material is a special Neodymium glass that effectively filters out selective wavelengths of low-pressure sodium and other manmade sources. Although it is not a nebula filter, it enhances the views of deep-sky galaxies and nebulae by increasing the contrast of these objects against the background sky. While nebula filters transmit only a few select wavelengths corresponding to various atomic lines, this filter transmits a large portion of the continuous spectrum, while blocking a few select lines of the more common manmade light.
This filter can also be used for lunar/planetary viewing. It increases planetary contrast and works especially well on Jupiter and Mars to help bring out subtle detail. Try it with the yellow filter of the Baader Premium 1.25" Colored Filter Set to bring out the surface features of Mars.
- Neodymium - unique, selective, blocking feature of the Neodymium element greatly reduces glare without reducing important color and brightness variations.
- Fine-polished, plane-parallel glass - eliminates any double images or ghosting due to wedge errors in the glass. As a result, it can be used in front of CCD cameras or high-power eyepieces without introducing optical defects.
- Multi-layer coatings on both surfaces - ultrahard and durable ion-beam hardened coatings, may be cleaned anytime without fear. Note: the 2" filter has a very hard, single layer MgF2 coating (Zeiss T coating). (See the Astro-Physics Optical Cleaning System (OPTCS) with its detailed instructions.)
- Very high light transmission - while blocking unwanted skyglow and many street light emissions. Transmission within the selected wave bands exceeds 95%.
- Filter cell design - large, clear aperture with no vignetting. The unique milled notches at the edge of the filter make it easy to grasp and turn, especially appreciated in the dark.
- Combine filters - standard 1.25" or 48 mm (2") eyepiece filter threads. It can be threaded onto other filters to allow stacking for narrower passbands. We recommend adding the yellow filter from the Baader Premium 1.25" or 2" Colored Filter Set to boost the contrast on Mars. When stacking filters on eyepieces, be careful that the eyepiece barrel, with the filters attached, does not strike the mirror or prism of your diagonal.