Baader Planetarium Dark Blue 435nm Bandpass Filter, 1.25" Eyepieces

It's the Baader Planetarium Dark Blue 435nm Bandpass Filter, a high-quality, durable, and effective tool for astrophotography and other optical applications. This innovative filter is specifically designed for 1.25" eyepieces and is renowned for its ability to block out certain wavelengths of light, allowing only specific colors to pass through. This feature enhances color accuracy, making it an essential accessory for those seeking precision in their observations.

The filter boasts a fine optical polish and 2mm thick glass, ensuring it can be seamlessly integrated into any optical path without introducing astigmatism or other defects. It's even suitable for use in front of a binocular viewer, enhancing the image without any degradation. The substrates of this reliable filter are free of striae and are plane-parallel polished to within 30 seconds of arc, effectively eliminating double images or ghosting due to wedge errors in the glass.

One of the standout features of this filter is its cell, which features the largest clear aperture of any telescope filter on the market. This ensures complete freedom from vignetting at any focal length. The front "crown" of the filter incorporates milled notches, simplifying handling and threading operations, even in low-light conditions.

The surfaces of the Baader Planetarium Dark Blue 435nm Bandpass Filter are treated with a 7-layer Multi-Coating, resulting in a mere 0.25% residual reflection. This is the most elaborate coating ever applied onto amateur color filters, ensuring a filter free of any false reflections under any incident angle of light.

Light is a crucial factor in all planetary observation, especially during high magnification work. The 7-layer MC-coatings not only provide a brighter image, but they also prevent the softening effect of scattered light, which can obscure subtle planetary surface details. The meticulous attention to coatings and perfect optical figuring are the reasons why the image contrast through these premium filters is so rock-solid. This filter is a testament to Baader Planetarium's commitment to producing high-quality, durable, and effective optical products.