How can I safely view the sun through my telescope

On Sun, 30 Jan 2000, Jan.Alicia.Aria wrote:

> I am interested in solar viewing with my 8 dob. However, I have been
> discouraged by many people who say it is too dangerous. Is this true?
> Is there a way to test the filter before I observe the sun? It is my
> understanding that imperfections in the filter can be invisible to the
> naked eye.

Hello,

It is true that solar viewing can be dangerous, but with the proper
filters or equipment, it is fairly safe to do.

First, never, ever use a solar filter that screw into an eyepiece. The
image of the sun comes to a focus near where these filters scrw in, and
the filter material can melt and crack, which would cause instant
permanent damage to your eyes.

The safest solar filters to use fit over the open aperture of the
telescope. Many companies make these filters, and you can find them
advertised in magazines such as Astronomy and Sky & Telescope. Thousand
Oaks Optical is one company that is well-regarded for creating
high-quality solar filters, although they are not the only high-quality
company. Their web site is:
http://www.thousandoaksoptical.com/

There are three types of aperture filters generally available: mylar,
polymer, and photographic. Mylar gives a bluish-colored sun, but is the
least expensive (generally). Polymer filters produce a yellowish-orange
image of the sun. Photographic filters are designed for camera systems
only!! They let UV and IR light through, and they let more light through
than the normal filter. This is great for taking pictures of the sun, but
it is dangerous to look through.

Finally, a completely safe way of viewing the sun is by projecting the
unfiltered sun onto a piece of cardboard held near the eyepiece. While
this may seem unscientific, it is totally safe. This projection method
also used to be the most popular method for solar astronomers to study the
sun, before high-quality cameras and solar filters were readily available.

Solar filters generally come with safety instructions. As long as you are
careful, viewing the sun through your Dob should be safe and very
interesting!

Good luck, and thanks for writing!

Sincerely,
Kurtis Williams

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