We recommend Baader ASTF and ASSF mounted solar filter films to those seeking an uncompromising and exceptionally safe solution for solar observation.
The solar filter naturally incorporates Baader's extremely popular, high-quality ND 5.0 film, optimised for visual use. The filter cell is made of metal and features holes into which "retaining pins" can be inserted, allowing it to be fitted to telescopes of various diameters. The package includes a set of self-adhesive hook-and-loop fasteners, allowing the solar filter film to be quickly and securely attached to the front of the tube. For Newtonian telescopes and refractors, the filter can be secured to the tube/dew shield from either the outside or the inside; for SC/MC telescopes, external mounting only is recommended.
In the ASTF series, the filter is housed in a temperature-compensating cell that expands and contracts together with the solar filter film as temperatures change, ensuring that the film always remains sufficiently taut to provide the best possible image quality.
The table below shows the sizing of Baader ASTF / ASSF filters. Use the outer diameter if you wish to mount the filter externally on the tube, and the inner diameter if you wish to mount it internally.
| Model | Clear aperture | Outer diameter | Inner diameter |
| ASTF 80 | 80 mm | 100 - 140 mm | 130 - 170 mm |
| ASSF 80 | 80 mm | 85 - 100 mm | 111 - 126 mm |
| ASTF 100 | 100 mm | 120 - 160 mm | 120 - 190 mm |
| ASSF 100 | 100 mm | 105 - 120 mm | 131 - 146 mm |
| ASSF 130 | 130 mm | 148 - 178 mm | 168 - 198 mm |
| ASTF 140 | 140 mm | 160 - 200 mm | 190 - 230 mm |
| ASSF 150 | 150 mm | 168 - 198 mm | 188 - 218 mm |
| ASTF 200 | 200 mm | 220 - 260 mm | 250 - 290 mm |
| ASTF 240 | 240 mm | 260 - 300 mm | 290 - 330 mm |