Direct Solar & Eclipse Viewing: References 
Author Message
 Direct Solar & Eclipse Viewing: References

(References are given below, but first some background...)

> I'm the ophthalmologist who was ranting. I guess is not the
> proper place for medical discussions.

SD: The charter of the group says it is the place...
SD: Clearly your statement carries baggage from the aformentioned discussion,
SD: which I didn't see, as previously noted.  What the hell happened anyway?

What happened was, a discussion developed after Dr. Peter Kastl made several
statements, some being gross exaggerations, while others were essentially
false.  For example,

> Many astronomy experts posted responses
> to me to set me straight about eclipses. Well, you told me. I'm glad you
> feel better. But you did one other thing...

> You caused someone to go blind.

Michael Covington has made an effort to try and sort things out:

MC: One last word concerning Dr Kastl's controversial opinon that the public
MC: should be told (falsely) that no filter is safe for solar viewing, simply
MC: because that if authorities admit that some filters are safe, people will
MC: injured from using filters that *aren't* safe.
MC: I don't agree, but let's understand that Dr Kastl didn't pluck this out of
MC: thin air -- it is a position often taken by medical authorities.

I think Dr. Kastl did pluck things out of the air.  I see three basic
problems with Kastl's postings:

        (1) Dr. Kastl made statements such as the following, and has
            failed to provide supporting references, except one (see below):

> The corona still has enough UV emission to damage the retina.
> But you can still get retinal damage during totality.

        (2) A check of the single mecical reference given by Dr.
            Kastl provided no support at all for his statements.


        (3) Dr. Kastl is reluctant to to modify his professional stance
            even after being given the necessary correct information:

> I consider this discussion closed. I will not read any more of these
> messages, and I will erase any e-mail about it, unread.

Below are excerpts from several references in the field of astronomy which
discuss safety issues with regard to viewing the Sun and solar eclipses.

In the second paragraph we learn according to Abell that, contrary to Dr.
Kastl, it is not only safe to directly observe the sun during totality,
but is safe to do so even through a telescope:

George O. Abell, "Exploration of the Universe," 4th Edition (1982), p. 150:

        "Common sense (and pain) prevents most of us from looking at
the sun directly on an ordinary day for more than a brief glance.  Of
course there is nothing about an eclipse that makes the radiation from
the sun more dangerous than it is any other time; on the contrary, we
receive less radiation from the sun when it is partially hidden by the
moon.  It is *never* safe, however, to look steadily at the sun when
it is still in *partial* eclipse; even the thin crescent of sunlight
visible a few minutes before totality has a surface brightness great
enough to burn and permanently destroy part of the retina.  Unless you
have a filter prepared especially for viewing the sun, it is best to
watch the partial phases with a pinhole camera device. [...]

        "It is *perfectly safe*, however, to look at the sun directly
when it is *totally eclipsed*, even through binoculars or telescopes.
Unfortunately, unnecessary panic has often been created by
well-meaning but uninformed public officials acting with the best

Notice below that not only is it safe to directly view the totally
eclipsed sun through a telescope, but without a solar filter as well:

Mark Littmann and Ken Wilcox, "Totality:  Eclipses of the Sun" (1991) p. 126:

        "Permanent eye damage can result from looking at the disk of
the Sun directly, or through a camera viewfinder, or with binoculars
or a telescope even when only a thin crescent of the Sun or Baily's
Beads remain.  The 1 percent of the Sun's surface still visible is
about 10,000 times brighter than the Full Moon.  Staring at the Sun
under such circumstances is like using a magnifying glass to focus
sunlight onto tender.  The retina is delicate and irreplaceable.
There is nothing a retinal surgeon will be able to do to help you.
Never look at the Sun outside of the total phase of an eclipse unless
you have adequate protection.
        "Of course once the Sun is entirely eclipsed, its bright
surface is hidden from view and it is safe to look directly at the
totally eclipsed Sun without any filters.  In fact, it is one of the
greatest sights in nature."

During the discussion on solar viewing we also heard this:


So far noone has bothered to provide a pointer to any reference by
someone in the medical community to support this extreme view.  Here
are two references I found by eye care specialists who disagree
with Kastl:


On pp. 130-131 in the Littmann and Wilcox book mentioned above, Lucian
V. Del Priore, M.D., writes in the section "Eye Damage From a Solar

        "There is nothing mysterious about the optical hazards of
eclipse viewing.  No evil spirits are released from the Sun during a
solar eclipse, and there is no scientific reason for running indoors
to avoid 'the harmful humors of the sun.'[...]
        "Viewing a partial eclipse recklessly is not the only way to
produce light-induced retinal damage [...] A solar eclipse merely
increases the number of potential victims, and brings the problem to
public attention."


Are there safe filters that can provide a proper "circumstance" for
direct solar viewing?  In "Safe Solar Filters", Sky & Telescope
magazine for August, 1991 (pp. 119-121), R. Ralph Chou (School of
Optometry, University of Waterloo) said:

        "The use of any filter for direct observation of the Sun is a
matter of great controversy.  Readers who have been active in
publicizing solar eclises during the past will recall the furor which
arose from advising the public on safe viewing methods.  With this
problem in mind, I collected several types of filter material for
testing and evaluation.  Since my professional interest is
radiation-induced damage to eye tissues, my evaluation of filter
safety was made with respect to preventing damage to the eye's

Chou concluded that filters do exist which are safe for direct solar

        "My results show that metal-coated glass or Mylar filters are
safe for visual and photographic work.  Properly treated
black-and-white film is safe when two layers are used.  And welder's
glass shade No. 14 is also safe for visual use.  Under no
circumstances should color film, smoked glass, or gelatin
neutral-density filters be used for direct solar observation."

The annular eclipse is almost two weeks behind us and some readers may
have already tired of the subject.  The issue now is at the next solar
eclipse, will things be any different?  Will eye care specialists
continue to rush people indoors to escape "the harmful humors of the
sun" in their "well-meaning but uninformed" ways?  Or might there be
an effort, in cooperation with astronomers, to alert the public to the
dangers of retinal damage, coming not from the eclipse but from the
photosphere of the Sun, while explaining what it is about the
photosphere that causes damage, and why it is safe to look at the
corona during totality when the photosphere is completely covered?

> I dare say that the people who tune in here don't care if the corona
> is attached to the sun or comes in a bottle from Mexico.

That is obvious from your postings.

Curtis Roelle

Sat, 09 Nov 1996 01:46:35 GMT
 [ 1 post ] 

 Relevant Pages 

1. Final News About eclipse. eclipse,solar eclipse,eclipse tank bag,moon eclipse,eclipse car audio

2. Most Recent News About eclipse. eclipse,solar eclipse,next lunar eclipse,read eclipse stephenie meyer online,lunar eclipse tonight

3. Solar eclipse eye injuries - Case reports solicited

4. solar system : Actual News. our solar system,formation of the solar system,solar system pictures,solar system school project,solar heating system

5. solar eclipse March 29

6. Solar eclipse eye injuries - Case reports solicited

7. Solar eclipse and eye damage - again

8. Problem with eyes after solar eclipse

9. Solar eclipse and eye damage

10. Eclipse or sun-viewing eye injuries

11. Eclipse or sun-viewing eye injuries

12. Final News About direct. direct tv,direct x,direct,discount tire direct,direct x 9 download

Powered by phpBB® Forum Software