Baader Planetarium 80mm AstroSolar BDSF 3.8 White-Light Digital Solar Filter for Telescopes

The Baader Digital Solar Filter with PHOTO-Film OD 3.8 is a development made possible after the product launch of our Baader Solar Filters OD 5.0 in spring 2015. The filter has the same cell and mechanical specifications as our ASTF-Filter with Safety Film OD 5.0, the only difference lies within the used AstroSolar Film - our AstroSolar PHOTO Film OD 3.8 which has proven itself over the years. This film allows shortest exposure times - mainly used for digital videography and the lucky imaging technique - and thus almost "freezes" turbulences in the earths atmosphere. AstroSolar PHOTO Film OD 3.8 is NOT intended to observe the sun, only for digital imaging!

Many ready made filters do stretch the filter material like a drumhead in order to make it look like a piece of glass - this absolutely does destroy the image quality, rendering the film useless for high magnification work. AstroSolar must be mounted entirely stress free in order to perform like a high precision plane optical window. It sounds like a contradiction with traditional perception of quality, but AstroSolar must show slight ripples! Only when the film is being put under stress by an improper cell mount it performs just like any single side coated glass-filter made of untreated float glass.

ASTF/BDSF (AstroSolar Telescope Filter) Baader DIGITAL Solar Filter for high-end Telescopes
This family of solar filters is made in the most elaborate way. AstroSolar must not be put under stress, neither during mounting the film, nor during any temperature change. For this reason the ASTF-Filter features a temperature compensated cell. The film itself is repeatably cemented onto an injection molded ring, whereas the substrate of that ring has the same thermal expansion like the Astro Solar Filter material itself.

This free floating film-carrier ring is held onto the aluminum frame with the help of another holding ring made of fiber reinforced plastic - for a maximum of security against breaking of the cell. This temperature compensated cell enables the AstroSolar filter material to retain its excellent optical quality at any temperature - be it -30deg.C or +50deg.C.