Can I use welder's glass along with a telescope to safely view the sun?

On Thu, 21 Sep 2000, Alan wrote:

> Howdy,
>
> If a solar filter (welder's glass #14) attenuates enough of the suns
> infrared/ultraviolet for safe *unaided* viewing of the sun, can I
> assume that it will also perform safely with a magnified image of the
> sun? (assuming it's in front and not getting heated up).

That is not a safe assumption, I'm afraid. I presume that you must be
using some sort of telescope or binoculars to view the sun. In addition
to magnifying an image, telescopes and binoculars also collect light from
a larger area than your eye and concentrate that light. So, while
welder's glasses might block out enough light for your eyes to glance
safely at the sun, the additional light collected by binoculars and
telescopes may be high enough to be dangerous.

Also, don't trust solar filters, whether purchased or homemade from
welder's glass, that are placed between your eye and the eyepiece of a
telescope or binoculars. The light from the sun gets focused to a point
there, and the intensity of the energy is enough to crack glass
unexpectedly, which would result in instant damage to your eye. Several
companies manufacture solar filters that fit over the aperture of the
telescope or binoculars, where they are completely safe.

You can read safety tips for viewing the sun at:
http://www.skypub.com/sights/eclipses/solar/safety.html

Thanks for writing!

Sincerely,
Kurtis Williams

Back to the Ask An Astronomer page.