ASTF: AstroSolar® Telescope Filter OD 5.1 – ClearWhite (80mm - 280mm)

Baader Solar Filters provide a safe way to observe and photograph the Sun with AstroSolar® ClearWhite Safety Film OD 5.1 in the best possible quality. In many homemade filters, the filter material is stretched tightly to make it look like a glass filter. However, this reduces the image quality and makes the filter unusable for higher magnifications. AstroSolar^® Safety Film must be mounted absolutely tension-free in order to act like a high-precision plane-polished optical window. Although this appears to contradict the usual perception of quality, AstroSolar^® must show slight waves. Only when the filter material is exposed to tension due to an inadequate holder does it perform no better than a simple glass filter made of optically untreated window glass.

The new AstroSolar® ClearWhite Safety Film OD 5.1 (100x50, 117x117cm) (various versions available) is a high-quality, double-sided metallized solar filter film designed for direct solar observation as well as for constructing front-mounted objective filters for telescopes, binoculars, spotting scopes, and camera lenses. It was developed to provide a particularly neutral, clear white solar image. Undesirable bluish or orange color casts, which may occur with simpler solar filters, are largely avoided.

The film has an optical density of OD 5.1 and reduces the intensity of sunlight by approximately 99.9992%, corresponding to a reduction factor of about 125,000. It complies with the applicable transmittance requirements of EN ISO 12312-2:2015 for filters intended for direct observation of the sun.

The film is manufactured from a special streak-free and bubble-free substrate and achieves an optical quality comparable to high-quality plane-parallel glass filters despite a thickness of only 0.012 mm. The material is not ordinary “Mylar” and was developed for exceptionally high uniformity and optical purity.

The double-sided coating ensures especially uniform filter performance and reduces the effect of isolated microscopic irregularities in the metallization. A single layer of AstroSolar^® ClearWhite Safety Film OD 5.1 is sufficient to produce a safe solar filter with excellent image sharpness.

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 -30°C or +50°C.

Included: ASTF Filter with apertures from 80 to 180mm (200 – 280mm not yet available) come with two sets of centering bolts in 38mm length. 3 bolts with 10mm diameter and 3 bolts with 20mm diameter, adjustable to the tube diameter of your telescope or dew cap. In addition three safety straps with glue-pads and three rubber plugs to cover the holes that are not used. 32-page instruction manual.

• original Baader AstroSolar^® Safety Film (OD 5.0), cell mounted and quality inspected by skilled members of our staff
• clear white IR-rejecting front ring with reinforcing raised edges along the outer and inner circumference, designed to protect the solar filter material from contact with any sharp metal edge
• 3 injection molded centering-bolts with threaded brass inserts to center the filter-cell in front of the tube opening. These bolts come in three different diameters, depending on the filter category (ASTF/ASSF/ASBF). Each bolt features injection molded rubber grip-faces, shaped to easily slide onto any telescope tube – but to come off very hard
• no tool mounting and adjustment of the centering bolts to fit a wide variety of mechanical tube diameters. Bolts made to contact the outside or optional (if appropriate) the inside of the optical instrument tube
• non-rotating sliding fasteners made from aluminum that hold the centering bolts. These metal sliders are equipped with a machined indicator to point towards the adjustment index
• additional Phillips screws are integrated into the sliding fasteners, so that the centering bolts can be firmly fastened with a screw driver if preferred by the user
• index scale provided beside each adjustment slot – adjacent to each sliding fastener, for fast and repeatable adjustment of the filter cell onto different telescope tubes
• black sliding washers supplied to securely cover the full length of the adjustment slots in the aluminum frame – for blocking sunlight from passing trough the filter cell beside the filter area
• three security straps included, to secure the position of the filter cell with Velcro-adhesive pads. A safety feature to absolutely ensure a secure fit in front of the telescope under any circumstances (gust of wind asf)
• warning text printed onto the front side of each filter cell: Read the Instructions before use
• cardboard gift box fit for safely shipping the filter
• Only for ASTF as well as ASSF 130/150 filters: Three rubber plugs serve as closures to close the unused additional adjustment openings.

Never look directly at the Sun without a suitable and undamaged solar filter. Normal sunglasses, emergency blankets, CDs, photographic neutral density filters or other untested aids are unsuitable for visual solar observation, as they may allow dangerous parts of non-visible light to pass through which, although not directly visible, can nevertheless cause lasting damage to eyesight!

A safe solar filter is also required during a partial or annular solar eclipse. Only during the short phase of complete totality of a total solar eclipse – when the photosphere of the Sun is completely covered by the Moon – can the solar corona be viewed without a filter. As soon as part of the solar disk is visible, a suitable solar filter must be used in any case.