Baader 70mm AstroSolar Filter for Binoculars (order two), fits 75-90mm OD (ASBF-70)

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The current solar maximum cycle will continue to peak throughout 2024 and beyond offering sunspots that will change and morph from one day to the next. Many people viewed the sun for the first time during the April 8th eclipse and were wowed by the level of activity. We encourage you to continue popping your scope out during the day to observe or photograph the progression of sunspots across the surface of our dynamic sun.

This filter version is similar to the ASSF in terms of mechanics. The only difference is that one side is cut off in order to make them usable on any binocular - even when the bridge is nearly closed. (depending on the binocular type). BAADER AstroSolar® filter material is mounted onto a plastic ring. The plastic ring itself works as stabilizing element for the filter cell. This ring is mounted onto the aluminum front frame. The thermal expansion coefficients of the plastic and the film are similar. 

  • Safe solar observation with all types of binoculars / safe solar photography with all camera lenses
  • AstroSolar® Safety Film OD 5.0, mounted stress free in high-quality cell
  • One side of filter cell shortened for use with binoculars. 

  • Two filters are mandatory for binoculars, price is for one piece only
  • Clear white IR-rejecting front ring with reinforced raised edges along the outer and inner circumference, designed to protect the solar filter material from contact with any sharp metal edge
  • Three (3) injection molded centering-bolts with threaded brass inserts to center the filter-cell in front of the tube opening. Each bolt features injection molded rubber grip-faces, shaped to easily slide onto any binocular or telescope tube - but to remain firmly mounted.
  • No tool needed for 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. Refer to Clamping Range of BAADER Solar Filters (inner/outer) for further details.
  • 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 through the filter cell beside the filter area.

  • Three (3) 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 binocular under any circumstances (ex. gust of wind).
  • Warning text printed onto the front side of each filter cell: Read the Instructions before use.
  • Cardboard gift box fit for safely shipping and storing the filter.

What's included:

  • ASBF Filter with 3 centering bolts (13mm diameter, 24mm length)
  • 3 Safety Straps with adhesive pads
  • Screws and washers
  • Instruction

Quick Reference for Astro-Physics Refractors, Binoculars and Finders.

  • Vario-Finder: ASBF-60
  • Stowaway (all models): ASBF-100. The flat side of this filter is especially useful if your Stowaway is mounted on top of another instrument.
  • AP 10.5x70, 11x70, 15x70 & 16x70 Binoculars  (sold in previous years, no longer available): ASBF-70

If you want to find a filter for a binocular, finder or camera not listed above, check this chart.

AstroSolar Safety Film to make your own filter

You may wish to construct your own filter from a sheet ofAstroSolar™  Safety Film using the instructions below. It is available in two sizes:

  • BAADER AstroSolar™ Density 5 - Visual, A4 size, 200 x 290mm (7.9" x 11.4")  (AS50A4) - each filter is packed in a stiff cardboard mailer with instruction sheets and chipboard for stiffness. As a bonus, the chipboard can used used to make your filter!!
  • BAADER AstroSolar™ Density 5 - Visual, 1/2 Meter size, 500 x 1000mm (19.7" x 39.4")  (AS50HM) - each filter roll and instruction sheets are packed in protective cardboard tube with 0.25" wall thickness within a box to ensure that it arrives safety to your door. 

Constructing a Solar Filter for Binoculars with BAADER AstroSolar Film

For more information, please refer to these documents :

Recommended Solar Filter Sizes – For Astro-Physics Refractors, Finder and Binoculars

Clamping Range of BAADER Solar Filters


The New Baader Solar Filters (BSF), Astronomy Technology Today, March-April 2015

Measuring your Telescope, Binocular, Finder or Camera

To ensure proper fit of the solar filter, you must measure the outside diameter of the dew shield or lens cell of your telescope or outside diameter of the binocular or camera lens. 
Metric conversion: 25.4mm = 1 inch. 


All solar filter sales are final. Please measure carefully before you place your order so that you order the correct size. Also, pay attention to the diameter of the filter material itself so that you select the filter that you want. For instance, it is possible to order a filter for a Traveler with only an 80mm diameter of AstroSolar® filter material. However you will likely prefer a filter with 100mm diameter of the actual filter material. Review all of the specifications carefully.