Baader Planetarium ASBF – AstroSolar® Binocular Filter OD 5.1 – ClearWhite

Optical Density (OD) 5.1 is a safety rating that indicates the filter blocks 99.999% of all sunlight, including harmful ultraviolet (UV) and infrared (IR) radiation. This level of attenuation is the international standard for safe, direct visual observation of the Sun through an optical instrument. Every ASBF filter meets this standard, ensuring your eyes are protected.

No. ASBF filters use Baader's "ClearWhite" AstroSolar® film, which is designed to provide a neutral, white-light view of the Sun. Unlike some filters that create an artificial orange or yellow image, these filters show the Sun in its natural color, which can make it easier to discern fine details in sunspots and faculae.

Choose the size that matches your binocular's objective aperture, e.g. the ASBF 50 for 10x50, the ASBF 80 for 15x80, or the ASBF 100 for 25x100 binoculars. Because the physical outer diameter of binocular barrels can vary between manufacturers, it is critical to measure the outside diameter of your binocular's front barrels before ordering to ensure a secure, light-proof fit. Both objectives must be covered, and each filter must fit snugly and not be at risk of falling off during use.

Absolutely. ASBF filters are perfect for observing all partial phases of a solar eclipse. With your binoculars, you can safely watch the Moon's disk move across the Sun. However, you must remove the filters during the brief period of totality to see the solar corona, and immediately replace them as soon as the Sun begins to reappear.

With a typical pair of 10x50 binoculars or larger astronomy binoculars and the matching ASBF filters, you can easily resolve key solar features. Depending on solar activity, you can expect to see:

• Sunspots: You can track the largest sunspot groups and often distinguish the darker inner umbra from the lighter surrounding penumbra.
• Granulation: Under steady atmospheric conditions, you may be able to see the mottled, rice-grain texture of the solar surface.
• Limb Darkening: You will notice the edge of the Sun appears slightly dimmer than the center, a phenomenon known as limb darkening.

AstroSolar® film is a specialized polymer that is more durable than many other solar films, but it still requires careful handling. Always inspect the filters for scratches, pinholes, or tears before every use, and never use a damaged filter. Store the filters in a protective case when not in use to prevent damage. With proper care, ASBF filters will provide many years of safe solar viewing.