Baader 1.25" and 2" Premium Colored Glass Filters (BPCF125)(BPCF2)
These premium 1.25" (BPCF125) and 2" (BPCF2) color filters from Baader Planetarium feature high-transmission, plane-parallel, optically polished glass, multi-coated with 7 layers on each surface. True plane-parallel surfaces eliminate ghost images at the eyepiece. The fine optical polish allows the filters to be inserted anywhere in the optical path without introducing astigmatism and other defects. Thus, they can be used with the Baader Giant Binocular Viewer or other similar products without concern about degradation of your image. All of these features assure fine planetary detail while preserving maximum sharpness and contrast in the image.
Both the 1.25" and 2" sets comprise three longpass and three genuine bandpass filters, which allow only a small portion of the visual spectrum to be transmitted in order to emphasize certain planetary surface detail.
Filters come in the following colors: Red (610nm), Orange (570nm), Green (500nm), Yellow (495nm), Blue (470nm) and Blue-Violet (435nm). The filters are only available in the U.S. in sets containing all six color filters.
- Fine-polished, plane-parallel glass - eliminates any double images or ghosting due to wedge errors in the glass. The glass is polished to within 30 seconds of arc.
- 7-layer multi-coat- features a mere 0.25% residual reflection, resulting in a filter free of any reflections of light at any angle. This prevents the softening effect of scattered light and loss of detail.
- Very high light transmission - allows the subltest planetary surface detail to be detected at high magnifications. Transmission efficiencies for the three longpass filters (Red, Orange and Yellow) peaks at approximately 98%, while the efficiency for the three bandpass filters peaks at almost 70%.
- 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> - All filters have standard 1.25" or 2" (48 mm) eyepiece filter threads and can be threaded together to allow stacking for narrower passbands. For instance, combining the Yellow filter with the Blue-Violet filter results in a very narrow dark green filter that transmits light only from 475nm to 500nm. You can also combine the color filters with other filters. We recommend the yellow filter with the Neodymium Moon & Skyglow filter 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.
Product description from Baader Planetarium - PDF file. The "TOOLS but Toys" header was intended to mean "It takes tools, not toys - for real achievement."