Looking Directly At The Sun Through A Pinhole

[Mark Robert Thorson]

I recently recalled that, as a child, I made the discovery that I could see
perfectly clearly without my glasses (I am near-sighted) by looking through
a pinhole. Now, about 20 years since the last time I did it, I made a
pinhole lens by poking a needle into a piece of aluminum foil. (Note: I
don't poke the needle through to its full diameter, just a little distance
past its point.)

I find that I can see quite sharply by bringing the pinhole within about
one-quarter inch (6 mm) of my eyeball. When looking at bright objects, I can
hold the pinhole about 1 inch (25 mm) from my eye, though the field of view
is rather narrowed at that distance.

My question is, can this pinhole be used for safely viewing the sun? Let's
say the pinhole would be held at a distance of one inch. The diameter of the
pinhole would be, at maximum, one-half the diameter of a thin sewing needle.

[Stephen Goldschmidt]

In article <19...@cup.portal.com> m...@cup.portal.com (Mark Robert Thorson) writes:
>My question is, can this pinhole be used for safely viewing the sun? Let's
>say the pinhole would be held at a distance of one inch. The diameter of the
>pinhole would be, at maximum, one-half the diameter of a thin sewing needle.

I wouldn't look directly at the sun under any circumstances. However,
you can use a pinhole to project an (inverted) image of the sun.
Any article on eclipse-watching will describe how to do this.

Stephen Goldschmidt (al...@portia.stanford.edu)

[Eugene Miya]

This is very dangerous.

What no other postings by knowledgeable people?
Projected image is okay.

But, they are your eyes. You have been warned.
Evolution in action.

Another gross generalization from

--eugene miya, NASA Ames Research Center, eug...@aurora.arc.nasa.gov
resident cynic at the Rock of Ages Home for Retired Hackers:
"You trust the `reply' command with all those different mailers out there?"
"If my mail does not reach you, please accept my apology."
{ncar,decwrl,hplabs,uunet}!ames!eugene
Live free or die.

[Mark Robert Thorson]

The responses I've gotten through postings and e-mail indicate that few,
if any, are familiar with the image viewed through a pinhole held up to the
eye.

The same effect can be observed by making a small aperture, as shown below:

fffffffffffffffffffffffffffffff rr
ffffffffffffffffffffffffffffff rrrr
fffffffffffffffffffffffffffff rrrrr
rrrrrr
ttttttttttttttttttttttttttttt rrrrrr
tttttttttttttttttttttttttttttt rrrrrr
tttttttttttttttttttttttttttttt rrrrrrr
rrrrrrr
In this diagram, f and t represent the left forefinger and thumb, firmly
pressed together. r represents the right forefinger, firmly pressed against
the junction of the other two (right-handers may wish to reverse these
positions).

In this configuration, you will get a small triangular opening where your
three fingers come together. By varying the force you apply with your fingers,
the size of the opening can be made arbitrarily small.

A small opening will let through a pinpoint of light when viewed from a distance
of about a foot (the distance at which the opening is just far enough away for
one eye to focus on it). As you bring the pinhole toward your eye, the opening
appears to enlarge from a tiny bright triangle into a dim disc. People who
wear glasses will notice that they can view sharp images in this disc without
using their glasses.

Adjusting the size of the opening affects the sharpness and the brightness
of the image in the disc. The size of the disc remains the same.

Holding a magnifying glass a foot or two from the opening makes a telescope.

Because the image is dim, it is easier to look at bright things. I am tempted
to think the sun would make an interesting observation. I think the disc of
the sun should look like it does when viewed through a blanket of overcast
clouds.