North American Skies for April 2001
| Click here for Solar Alert Information: SpaceWeather.com |
JUNE 2002 Addendum: Never, ever look directly at the Sun or a direct reflection of the Sun. However, if you use appropriate precautions, you can observe the Sun safely. One way is the use an appropriately shaded pair of binoculars as in this graphic:
Keep in mind that you must never look through the binoculars at the Sun, and you must take precautions to prevent children or uninformed persons from doing so. Also be sure not to focus this light on pets or any flammable object as it can get very hot. In fact, you should not use this method for more than about a minute at a time because the optics of the binoculars can get too hot and crack.
If you do not have binoculars, you can still try in this manner:
With the Sun still at
a high level of activity and the prospect of continued large sunspots and
auroras for the next several months, I thought it was appropriate to revisit the
topic of viewing the Sun safely.
ллл--- Click on the image for a more detailed view.
Certain risks are involved in any attempt to observe the Sun directly or indirectly. Remember that any direct observation of the Sun -- whether it be through a telescope, binoculars, sunglasses or with just your eyes -- is extremely dangerous and likely will reward you with vision loss. Don't do it!
However, if you take the proper precautions, it is possible to
project a simple image of the Sun on which you can sometimes even see large
sunspots. (One method was detailed in the October 2000 article: "At Sunspot Maximum?") For
several years I have assigned my students the simply project of measuring the
Sun's diameter using this projection method. You don't need to measure anything,
but if you want to see a large sunspot for yourself, keep tabs on the solar
activity by frequently visiting Spaceweather.com or simply checking out
the image below, which is the latest available from the Solar Data Analysis Center.
When a really big one is visible on the Sun's surface, you can observe it on
your own with nothing more than a small mirror and a steady hand.
Simply take a small flat mirror (not a curved or magnifying mirror), and cover it with an index card on which you have cut out about a quarter-inch hole. The exact size or even exact shape of the hole is not important. Effectively what you are doing is stopping the mirror down to a small size. Now reflect the Sun's light through the mirror onto a flat surface in the shade. With a quarter inch mirror, you will need to project the beam about 15-20 feet to get a good image. This is a modification of the old "pinhole" lens technique. The important thing is that you project the image at least 800 to 1000 times the width of the mirror (cutout).
There are two important cautions here. First, the image will be faint and small. In this scenario, it will be about 2 inches across. In order to see it well, you will have to project it onto a white surface in a darkened area, such as a garage or through a window into a darkened room.
Second, the image will be very difficult to hold still. I suggest that you rig a device to allow you to aim the mirror and then lock it into place. I have glued a small mirror to the lens cap of a camera mounted on a tripod. Then I could aim it, lock it in place, and walk over to the wall to examine it. Even doing it this way, however, the image will move because the Earth is rotating out from under the Sun.
Here are some photos from one of my students, Patti Sand, from the Spring semester 2001:
 |
Patti covered a compact mirror with a piece of paper into which she
had made a small hole with a ordinary hole punch. Then she attached it to
the camera mount attachment for her tripod.
Image copyright 2001 by Patti L. Sand | |
| Having attached this assembly to the tripod, she
was ready to aim her projection of the Sun onto an appropriate wall, and
lock the tripod down.
Image copyright 2001 by Patti L. Sand |
 | |
 |
Since it is best to shoot the image into a darkened area, she aimed
the solar reflection through a door into a a room with lights off and
windows covered.
Image copyright 2001 by Patti L. Sand | |
| She aimed the projection directly onto a piece
of white paper. The markings you can see on the solar image are not
sunspots in this case (there were no big ones at the time), but rather
Patti's position markings on the paper. The image is oval due to the
camera angle. Note that the image will move fairly quickly across the
wall, due to the Earth's rotation, and will have to be repositioned.
Image copyright 2001 by Patti L. Sand |
 |
You can use a larger mirror, but you also will have to use a longer throw. A 2 inch mirror at about 150 feet will give you about the same level of detail, but the image will be larger, and you will still need a darkened area. I have done it with a 3 inch mirror at about 100 feet. In this case it will produce a round but fuzzy image of the Sun, useful during solar eclipses but no good for viewing sunspots.
By the way, the shape of the mirror is irrelevant if the mirror diameter to distance throw ratio is very small. If the distance thrown is ver short, the mirror shape will be what you see (such as square or rectangle) and it will not represent the proper shape of the Sun.
Another reminder: Any direct observation of the Sun -- whether it be through a telescope, binoculars, sunglasses or with just your eyes -- is extremely dangerous and may severely damage your eyesight. Be especially careful monitoring any children around when you attempt the observation of the Sun suggested in this article. Neither North American Skies, its writers, contributors, relatives, neighbors, nor anyone in a 100 mile radius can be held responsible for damage done to eyes or anything else -- due to negligence, acts of God or any other cause -- while attempting to observe the Sun. We have warned you. Act responsibly. Observe at your own risk!
Larry Sessions
According to Kim Long in his book, The
Moon Book, (Johnson Books, Boulder, CO) the Full Moon of April (4th full
moon of the year) was known as the "Moon of Grass Appearing" to the Lakota, and
the "Leaf Split Moon" to the People of the San Juan Pueblo, and "Little Frogs
Croak Moon" to the Oto. To learn more about the American names for the various
moons, and mounds of other information, grab a copy of The
Moon Book.
This article and all of North American Skies are copyright 2001 by Final Copy, Inc. , except for portions identified as copyright by their respective authors.
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