Sun snapshot

[Brian]

Lumix TZ18 and Astrosolar safety film. camera time UT

[michael feist]

Interesting shot, Brian.
I have wondered to what degree of safety there is in trying to photograph the Sun through #14 welding glass, and viewing the the image in the back of the camera to find and to focus. Not too worried about the camera but rather my eyes. The #14 is fine for naked-eye viewing, and this welding glass was bought many years ago to view eclipses. But I have been very uncertain to what degree this applies to thro' the camera, to the back screen. Any ideas.
Regards mf

[brian livesey]

The No.14 welding glass is difficult to get here in tool shops. I have to make do with a No.13. When using it on the Sun, I slant it to make the image darker.

[Brian]

Hello Mike. I think that the Suns image on the rear screen of the camera is quite safe to view. I would be more concerned about the possible damage to the imaging chip itself if the dark glass transmits too much energy. My astrosolar film is Nd=5 if I remember correctly. I'm not sure what the Nd value of the No14 welding glass is. Maybe David can help here. Also if you use the camera lens to zoom in, the image on the sensor and the transmitted energy get spread out and "diluted" considerably in the process.

Regards,

[David Frydman]

Hi Brian,

The steps with welders glass are the 7th root of 1000, that is 2.68x.

So a welders glass 14 is 2.68x darker than a welders glass 13.

But I am not sure where the scale starts.

A welders 15 would be 0ne million times darker than a welders 1 if it exists.

I used welders 13 large size and tilted it till it reached an optimum density.

However, because my eyes have worsened I no longer do solar observing of any kind.

The RAS did have some information on welders glasses for solar viewing, but I don't have a link.

I have never used astro film and am horrified by the German user of astro film on a 30 inch Dobsonian scope.

A pigeon flying into the film and the eye is fried.

Using a Galilean finder on a camera must be a no go with the Sun, but I am not sure about the screen.

Regards,
David

[David Frydman]

It is not recommended to stack welders glasses.

Apparently a welders 7 and welders 8 do not give the same protection as a welders 15.

In high U.S. locations welders 15 are used.

The eclipse glasses vary in density, I think some are equivalent to welders 15 or 15.5.
But I find the optical quality considerably worse than welders glasses with EU or BSI kite markings.
The eclipse glasses also have recommended daily limits on using time.
They also have a five year shelf life.

I have never seen a shelf life mentioned for welders glasses.
It would be interesting to know what it is.

A steel worker admitted to having had welders arc damage to his eyes from years in a steel plant, maybe in Sheffield.
The photos of him and his mate at work look like the colonisation of Mars snapshots.

Never use a welders glass without the shade number printed on it.
It may be shade 8.

Always minimise the time one observes the Sun.

Regards,
David

[brian livesey]

Baader solar film gets a good press. It doesn’t seem to oxidise over time. An experienced and knowledgable solar observer on solarchat.com said he was still using the same piece of Baader film on the front of a refractor for ten years.

[David Frydman]

I would ask Baader what the safe life of their film is.

Degradation may be so slow the user definitely doesn't notice.

The best tests are done by university laboratories that deal with these matters.

I had this done with the rogue seller from Nottingham of totally unsafe so called solar filters.
He even popped up again under another name.
The BAA apologised for taking his adverts.
A barrister helped.
The so called filter transmitted up to 27% in the infra red.

It all cost nothing except enormous amounts of work.
Had we paid it would have been over £1,000 just to get one rogue seller to stop.

Solar filters still turn up on the back of eyepieces.

One needs to get accurate information.

Regards,
David

[jeff.stevens]

If never considered the shelf life of Baader film. Thinking about it, mine must be approaching 10 years old. I might invest some new film.

Best wishes, Jeff.

[michael feist]

DIRECT viewing the Sun is so fraught with possible dangers that, apart from the occasional use of the #14 welders glass to get quick views of Solar Eclipses or the setting Sun, simply projection on a white screen with a small scope or binocular is probable the best, even if the eyepiece stop does gets damaged - I have heard it called a 'sacrificial eyepiece'. Better than a 'sacrificial eye'!!
Of course if you can afford one of those Hα scopes ... (I used to have one, but sunspots became so rare at that time, that I sold it!).

Regards mike f.

[Brian]

My Astrosolar filter works at ND 5.0

Baader say for Astrosolar Film:
"Baader AstroSolar Safety Film is made for the construction of high-quality objective-filters for observing the sun with telescopes, binoculars, camera or video-lenses. This foil is CE-tested and reduces the intensity of sunlight by 99.999%"
and
"Eye safety
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! Baader AstroSolar™ safety film has been approved for eye safety by the National Bureau of Standards in Germany, the PTB. Unlike any other Solar Filter on the market, AstroSolar™ is CE-tested according to EG-Norm 89/686 and EN 169/92 (notified body 0196). All processes connected to this product have been thoroughly tested. Coatings are inspected constantly for consistency to ensure your eye safety! "

For telescopic observation with Astrosolar filter I always additionally fit an IR=cut filter to the eyepiece. If imaging I fit an IR-cut filter to my astro-camera if one is not already present. Typically "non-astro" cameras already have an IR-cut filter over the imaging chip,

regards,

[David Frydman]

What it does not say is how long any warranty is, or for how long it is safe.

That is really important and should be stated.

If there is a limited time, as there must be, does each roll have a date marked.

And again.

What is the shelf life unused?

What is the use time?

What are the temperature limits?

Regards,
David