The Safe Solar Viewer Community Page

for the 1-Lens SSV

Here you will find information on how to make a 1-lens SSV using a lens from ordinary reading glasses. Making one is so simple it could easily be constructed the day before an eclipse or even the hour before first contact. All that is needed is the right lens, some cardboard, glue and tape. It is a good project for youth groups because the lenses are inexpensive and cardboard boxes can be free.

It is surprisingly easy to make a 1-lens SSV. Take a pair of reading glasses outside in the sunlight, cover one of the lenses and let sunlight pass through the other lens. You will notice it forms a spot of light on the ground. Now move the lens either closer to or farther from the ground until the spot is the smallest. There you are! The spot is an image of the Sun and you have made a crude SSV. I like the 1-lens SSV because it provides a brighter, sharper image than the pinhole viewer at a very affordable price. After you have gathered the materials, construction takes a matter of minutes.

For the optics, obtain a lens from a pair of reading glasses. We prefer a +1 or +1.25 diopter lens but anything up to a +2 lens works although for the +2 lens the solar image is half the size produced by the +1 diopter one; however the SSV is half as long and easier for a young child to deal with. We purchased our reading glasses from Dollar Tree and the recent cost was a little over a dollar. (A +1 close-up camera filter will work just as well but usually cost more and they are less common today that they used to be.) The +1 lenses have a focal length of 1.0 meter (39.4 inches) and produce an image of the Sun about 1 cm (0.4 inches) across. The +1.25 lenses Have a focal length of 0.8 meters (31.5 inches) and produce an image of the Sun about 0.8 cm (0.3 inches) across. Either of these lenses produce images easily large enough to show the partial phases of a solar eclipse very well. They are not as well suited to show the eclipse to groups as the 2-lens SSV, but they make a fine personal viewer.

If you are working with a club or a scout group and having children make these viewers, then we suggest you order from Dollar Tree's web site where their reading glasses are sold only in case quantities. The glasses with plastic lenses come 36 to a case and thus hold lenses for 72 SSVs. Shipping to a Dollar Tree near you is free but you can also have them shipped directly to you at a very reasonable cost. (Note: neither the editor of this web site nor the College of Charleston gain any financial benefit from promoting Dollar Tree.)

The next step in making a 1-lens SSV is to obtain or make a support long enough to hold the lens at one end and a piece of white paper at the proper distance at the other end. SSV Community members have made these supports of wood, foam board and other materials but they are very easy to make using cardboard boxes.

If you are helping a group of youngsters make 1-lens SSVs, constructing a large number of boxes is a time-consuming job. Also it requires more skill and patience than most children have, so having the kids make their own boxes seems impractical. In such cases we recommend using standard long shipping boxes of the appropriate length. Uline, a shipping supply company, has a number of suitable boxes of the right length for the job. In Table I we have listed the catalog number of a proper size Uline box for each different strength lens.

Uline does not have boxes identical in length to the focal lengths of the lenses we are using, but those discrepancies are all 2% or less and that is small enough to be ignored, especially since we are stopping down the size of the lens to an opening to no more than half an inch or less across. Stopping down increases the "depth of field" of the lens and allows quite a variation in focal distance without decreasing sharpness. Those of you familiar with the technical aspects of photography are familiar with the effect.

Unfortunately for 32-inch and 40-inch SSVs Uline does not offer boxes in a 4 x 4 option. A 6-inch box is bigger than necessary but certainly will certainly do the job as well as a narrower box.

If you are only constructing one or two SSVs then making a box or two is a simple enough task. We find it best if you find a longer box with a suitable dimension for the width and cut it down to size.

Figure 2a. An SSV using a +1 reading glass lens mounted in a cardboard box cut down from a larger one. (See more ideas here on cutting boxes to make a viewer.) The clips holding the front of the box can in place can be removed after checking the image and gluing lens holder in place. The distance between the the lens and the white screen depends on the power of the reading glass lens and is given in Table I above.

Figure 2b. The original box was 5 by 14 by 56 inches. We kept the 5 inch dimension and ended up with a box 5 by 5 by about 43 inches after we trimmed the box and glued it back together. We trimmed about 10-12 inches from the end of the box and mounted the reading glass lens on the outside of small side of the  box. As shown in Figure 2a, the part of the box holding the lens can be slid up and down the box to adjust the distance between the lens and the screen. After the proper position of the lens is established, the lens holder is glued into place and your SSV is complete. Since this viewer was using a +1 one eyeglass, the distance between the lens and the screen was set at 39.4-inches and glued into place.

We wish to remind all operators of SSVs that they are not toys and should not be available to youngsters to play with unless they are fully supervised and observed at all times. The 1-lens SSV is probably safer than the 2-lens SSV or a pair of reading glasses that a child could take outside, but still an abundance of caution is needed and is little trouble to accomplish. If the lens is taped on as in Figure 3b, then removing the lens and putting it in the operator's pocket or purse when leaving the viewer unattended, renders it entirely safe. The purpose of the SSV is to permit safe observation with little chance of harm.

We also encourage all makers of SSV to attach labels warning people not to try to look through them to look at the Sun and to keep children from do the same.