AstroSolar Photo Film OD 3.8

There is no back- or frontside on our AstroSolar film. It is equally coated on both sides, so you can use it either way for building your solar filter.

For a camera lens, you are better of with the regular (visual) ND5 film - the photo-film is made for slow f/ratios (like f/30), which are achieved by a telescope in eyepiece projection, but not with a camera lens. Wit a camera lens and ND3.8, the image will be much too bright. Please also take a look at our FAQ at https://astrosolar.com/en/faqs/ where we answered this and other questions more in detail. Concerning other manufacturers: Comperative advertizing is prohibited in Germany. If you do your own research in the web, you will find countless opinions on all the materials mentioned. Please choose from these exellent sources what is the best.

You can either buy BDSF: OD 3.8 Baader Digital Solar Filter 160mm #2459374 which comes mounted in a temperature-compensating filter cell, or you build your own filter cell as described here: https://www.baader-planetarium.com/en/downloads/dl/file/id/338/product/3044/how_to_make_your_own_photo_solar_filter_for_cameras_and_telescopes.pdf and here https://astrosolar.com/en/information/how-to/

No, the film has the same coating on both sides and it doesn't matter which side you will face to the sun.

For exactly this purpose we do supply the ASTF-series of mounted solar filters. The fastening rim on which the film is affixed to has the same expansion coefficient as the film itself. and that very ring is free-floating in the cell that mounts onto the telescope tube. Hence there is no stress build-up extended onto the film as it shrinks with temperature variation. The film itself will not be harmed by temperatures between -50°C up to +50°C. Below the film will become stiff and further below (- 100°C) even brittle. Above 50°C the adhesive that fastens the film onto its mounting-ring may start to become soft - in case that temperature persists for longer than 24 hours.