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From: tj@alliant.UUCP (Tom Jaskiewicz)
Newsgroups: sci.astro
Subject: Re: Solar Filters
Message-ID: <332@alliant.UUCP>
Date: Thu, 16-Oct-86 18:56:45 EDT
Article-I.D.: alliant.332
Posted: Thu Oct 16 18:56:45 1986
Date-Received: Tue, 21-Oct-86 08:08:16 EDT
Reply-To: tj@alliant.UUCP (Tom Jaskiewicz)
Organization: Alliant Computer Systems, Acton, MA
Lines: 30
Summary: Don't use welder's glass

In an article, somebody writes:
>
>>surface, like a screen or flat sheet.  Or you may want to use a safe
>>filter.  An easy, cheap filter is welder's glass  -- number 14 or
>>darker.  Just look in the yellow pages under "welding supplies." Give
>
>   Would this be good for making a homemade solar filter for a telescope?
>I would probably make the type that fits over the end of the scope tube.
>
>   Would it be safe???

NO!

The spectrum produced by arc-welding is DIFFERENT than the solar
spectrum.  Welder's glass will not necessarily protect your eyes while
viewing the sun.

I've heard of one scientist who used his lab equipment to test welder's
glass.  He found that sometimes it will work, and sometimes it won't.
It depends who the manufacturer is.  (I heard this in 1983).

Similarly, what harms a camera is different than what will harm your
eyes.  A 5.0 or 6.0 neutral density photographic filter will let you
take a picture of the sun, but won't protect your eyes if you look
through it.

-- 
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