Solar film safety

[markse68]

Never having looked at the sun before i’m naturally a little bit wary! I was given a film type solar filter with my new scope yesterday and I’m not sure i trust it. It’s a Chinese item rather than a named brand but i expect the Baader film is probably made in China anyway so not sure that’s reason to doubt it. Mainly i’m worried as although if i hold it up to a bright light I can’t see any light passing through pinholes etc, I did hold it over a spotlight and using a 10x loupe I can see really tiny pin holes that do pass some light though it’s not really bright.

But then on FLO’s description of the Baader film it says this:

”AstroSolar™ is essentially free from pinholes, since - other than with even the most expensive glass filters - it is coated on both sides, so that the chance of two pinholes overlapping each other is extremely faint. Pinholes do appear, but to 1 out of 10000 only in optical density 2.5! ”

So it can have pinholes in the coating too!

So should I be worried? Is it safe? I’ll probably buy a new film or ready made filter assembly just out of paranoia anyway.

Mark

[johninderby]

Small pinholes actually aren’t a problem. This is from Baader’s instructions.

Before each solar session carefully inspect your AstroSolar filter for mechanical damages, broad scratches, streaks, extensive whipe marks and other quality degrading influences. Small pinholes do not degrade the eye safety or image sharpness of AstroSolar.
 Hold the filter at arms length towards the daylight sun to detect dangerous defects. Small pinholes may become visible but will not be dangerous, because the light going through will be dispersed across a wide area like in a “camera obscura”. This scattered light however will cast a “hue of light” to slightly overlay the solar image information and reduce image contrast somewhat.
For highest photographic performace and when using large telescope apertures at high magnification it is therefore advisable to “blacken out” these pinholes. Use thick black laquer (black paint) and directly apply the paint onto the inner (telescope) side of AstroSolar with a very thin, sharp brush to just cover the size of the pinhole while holding the filter towards the sun.
 

BTW the genuine Baader film is made in Germany.

Edited April 14, 2021 by johninderby

[markse68]

Thanks John, that’s very reassuring.

Mark

PS it looks like this filter which says it uses Baader film anyway so should be good

https://www.microglobe.co.uk/levenhuk-solar-filter-for-120mm-refractor-telescopes-p-20664.html

Edited April 14, 2021 by markse68

[Floater]

I would certainly be happy to use it, given your description and how it appears in your pic.

That said, it is you who must be happy to use it ... 

I hope the reassurance you have been given is enough. 😎