Baader Planetarium 140mm AstroSolar Telescope Filter OD 5.0

140 mm AstroSolar solar filter

The Baader Planetarium 140 mm AstroSolar Telescope Filter is a dedicated white-light solar filter for telescopes with apertures up to 140 mm. It uses Baader AstroSolar Safety Film rated at optical density 5.0 for safe visual observation and imaging of the Sun. The film is mounted stress-free to maintain high precision optical flatness. A clear white IR-rejecting front ring with raised edges protects the delicate film material from contact damage.

Upgrades from improvised or stretched-film filters

This filter replaces makeshift solar filters that stretch film tightly over a cell, a method that distorts the optical surface and degrades image quality. The stress-free mounting preserves the film's plane optical window performance, delivering sharper contrast and finer solar detail. The jump is worth it for observers who want consistent, high-resolution views of sunspots, granulation and faculae without the aberrations introduced by tensioned film.

Tool-free adjustable mounting

Installation requires no tools thanks to adjustable centering bolts and non-rotating aluminium sliding fasteners that accommodate a wide range of mechanical tube diameters. The sliding fasteners lock the bolts securely without twisting the filter cell during tightening. What usually goes wrong is overtightening the centering bolts, which can deform the cell or pinch the film; apply only enough pressure to hold the filter firmly without flexing the frame.