astrosolar_differences

Differences in AstroSolar® Solar Films

We produce three different kinds of Baader AstroSolar™ Solar filter films and additionally Baader TurboFilm™ for protecting your optics

In the following we explain the differences in using these filters.  For information about the optical and technical properties of the telescope films (AstroSolar™Safety Film and AstroSolar™ Photo Film) turn to the section: general technical information

AstroSolar™ Safety Film (OD 5.0)

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This patened film is being produced for visual and photographic solar observation at high magnification. AstroSolar Safety Film is best suited for precision work with all astronomical telescopes and binoculars – just as well as for all photographic camera- and tele-lenses

When using AstroSolar™ Safety Film – mounted in front of your optics – you can image the Sun and safely look through the viewfinder of your camera – or you can directly look into the Sun with telescopes and binoculars at any suitable magnification.

The light blocking properties of AstroSolar™ SafetyFilm have been verified by the German Bureau of Standards (PTB) to be 99,999%. Conformity with existing EU-regulations for eye safety are certified by the CE-Symbol.

The optical density of OD 5.0 means that solar radiation intensity is being reduced to 1 : 100 000 of the initial value. Multiple coating processes on both sides of the carrier film are adding up during production to result in a perfectly uniform filtering result and help in neutralizing the effect of microscopic pores in the coating hat plague conventional glass solar filters which are commonly only coated on one side of the glass.

One single layer of AstroSolar™ Safety Film is perfectly apt to enable production of a safe solar-filter, suitable to supply highest contrast and sharpness in combination with your telescope or camera tele-lens. We produce this diffraction limited filter material since more than 15 years.

AstroSolar™ Silver Film (OD 5.0)

AstroSolar™-Silver Film has been specially developed for visual solar observation at zero magnification for use with solar viewers. This film is only being used for production of our Solar Viewers

The neutral density of AstroSolar™ Silver Film likewise amounts to OD 5.0 and is CE-certified.

This film has no added treatments to attain fine-optical properties necessary for high magnification work. It is not suited to being used for telescopes or camera lenses.

We are producing Baader AstroSolar™ SilverFilm since more than 25 years. In the year 1999, during the grand total eclipse over Europe, more than 20 million solar viewers equipped with this film were in use.

Why don’t we use this film for telescopes – a simple answer:

When using precision-grade AstroSolar™ Safety Film for telescopes, perfect optical quality is most important. However – this film must be treated with great care since the metal and protective coatings applied onto both sides of the film are very similar in their technical properties to the reflective surface applied onto astronomical mirrors.

Since a Solar Viewer is used visually at zero magnification, the optical grade of the film is not of prime consideration. Instead it is most desirable to apply protective coatings of highest durability grade, to end up with a protective film of much higher resilience against inadverted rough handling. This is being achieved for AstroSolar Silver Film with its metal hard coated layers applied onto both sides of the film,
making it scratch resistant without sacrificing in sharpness and without creating a double image of the Sun due to adding up several layers of dark and/or reflective film onto each other.

A single layer of AstroSolar™Silver Film provides a perfectly sharp and energy balanced solar image – including the ability of identifying large sunspots and without transmitting irresponsible amounts of infrared(heat) radiation as with simpler sooth-filled energy absorbent films which do not offer added IR-blocking by metal reflective coatings.

AstroSolar™ Foto Film (OD 3.8)

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AstroSolar Photo Film OD 3.8 is only intended to be used by well-experienced Astro-imagers. This material is not intended to serve for protection during visual solar observation. Also PhotoFilm is not necessary for imaging the sun with camera- or tele-lenses, or in the prime focus of most telescopes. The resulting exposure time would be much too short, respectively the results would cause severely overexposed images. Instead, you can use AstroSolar Safety Film ND5 (for visual use) with a modern camera up to a focal ratio of ca. f/15 to f/20 – even at ISO 100.

Photo Film solely is used in conjunction with astronomical telescopes – and only in connection with fast digital video cameras. This combination is highly apt to capture finest solar surface detail and granulation at extremely high magnification – but enabling ultrashort exposure increments measured in milliseconds – in order to “freeze” atmospheric turbulence . The results are quite outstanding as can be seen in the image gallery and in the customer reports.

Do not use this material until you are convinced to having gained sufficient experience with the hazards of Solar videography while using regular AstroSolar™Safety Film ND 5.0.

PhotoFilm OD 3.8 consists of the same optically treated carrier film with just diffraction limited properties as our AstroSolar Safety Film with optical density 5.0. The density of the adjacent multiple coatings however has been reduced for Photo Film in a very controlled fashion. OD 3.8 constitutes the border line, to still offer an absolute minimum of eye safety, in case someone would handle with the film and – in spite of extensive care – would accidentally catch up a split second view of the intense solar energy near focus. Still every amount of precaution must be undertaken to avoid just this to happen.

Sadly AstroSolar Photofilm OD 3.8 may not be used for visual solar observation – not even in combination with additional neutral density filters nor other filters of any kind. Reason being: none such filter combo has been tested by any licensed authority for eye safety. Surely such combinations may exist and they may produce magnificent and interesting views with sufficient reduction of solar energy across a safe enough spectral passband. However – as a manufacturer – we would be obliged to warrant for sufficient eye safety and provide safety evidence for an innumerable amount of possible filter combinations each having it´s own CE-certification.
For this reason we must leave it with the clear statement that we do not approve of any other use for AstroSolar™ PhotoFilm than described above.

Many astronomical Oldhands have asked repeatedly in recent years to produce an even brighter version of PhotoFilm in order to achieve even shorter delivery times. Unfortunately today nobody could or should offer such a product with his mind in peace. Just 20 years ago Carl Zeiss could afford to offer single side coated (and pinhole prone) photographic glass filters stopped to OD 3.5 – and offer them without any excessive warnings nor safety measures for photographic use with slow emulsion based SLR-cameras. In the contrary – the only warning read: “pinholes are common in solar filters. If found objectionable opaque with sharp brush and black paint”. Modern times product safety regulations do not allow to offer so bright and single side coated solar filters anymore.

Posted in About AstroSolar® Solar Film.