Baader AstroSolar Safety Film Information

This page provides additional information about Baader solar film, compiled from various sources.

1. Technical Specifications
2. Cleaning AstroSolar Film

1. Technical Specifications

- AstroSolar Safety Film is a specially manufactured streak- and blister-free foil only 0.012mm thick.
- The film is manufactured by Baader Planetarium, Germany.
- The base material is not Mylar. The quality of the solar image is immeasurably better than can be achieved by using so-called Mylar "rescue blankets" or similar materials.
- The basic development of this precision film was made in laboratories for nuclear and particle physics. Due to it's absolute homogeneity, the foil attains the optical performance of high quality plane-parallel glass filters.
- High density coatings on both sides of the foil ensure a highly uniform filtering capacity without pinhole effect, resulting in an extremely contrasty solar image with neutral density characteristics. The Sun appears in its real color - neutral white - not blue or orange.
- The coating of AstroSolar Safety Film is subject to constant quality control. Its reflective property (reduces intensity of sunlight by over 99.999%, i.e., by a factor of over 100,000 in the case of visual film) and security for direct solar observation is tested repeatedly by the PTB (German National Bureau of Standards for Eye Safety).
- One layer of this foil is sufficient for the construction of a safe, high resolution solar filter.
- AstroSolar film is available in two densities, ND5 (0.00001 transmission) for direct visual use, and ND3.8 (0.00016 transmission) for photography only. We stock both types.

(Source: "Baader AstroSolar Safety Film" and "Original Baader AstroSolar Safety Film" information sheets, distributed by Baader Planetarium Astronomical Instruments, Germany)

2. Cleaning AstroSolar Film

We strongly recommend that you store your completed filter in a container to protect it from dust and damage when you are not using it. Similarly, protect any unused filter material so that it is in new condition when you need it. Fingerprints on a metallized surface are to be avoided under all circumstances. It has the same consequence as putting fingerprints onto a telescope mirror.

Since your AstroSolar filter will be open to dirt and dust, the coating may require cleaning after extended exposure. If the dust is loose, you may be able to blow it off with compressed air or an airbulb, both available in camera stores. Since the coating is harder than regular aluminum coatings applied on mirror surfaces, it can be cleaned with a solution of dishwater detergent and distilled water. Obtain sterilized cotton wool (as used for eye application), available in pharmacies. Normal cotton wool as used for cosmetic purposes should NOT be used!

Use careful, gentle strokes. For each stroke, a new portion of cotton is to be used, soaked with the cleaning solution. This helps to avoid scratches in the metal surface due to dust grains picked up by the cotton.

Check the cleaning result by holding the cleaned filter up to the Sun. If scratches or pinholes show up, exceeding a combined uncoated area of 10 square mm, the film is regarded as unsafe and must be destroyed. Tiny pinholes can be covered with a black felt-tip marker. If the filter becomes very dirty, we encourage you to replace it, rather than risk damage in the cleaning process.

(Source: Astro-Physics, Inc., Rockford, IL,