Techniques for Watching Solar Eclipses

-Bill Kramer
 

The Basic Rule: Never look directly at the sun. The result can damage your eyes.

It is not a good idea to look directly at the sun since it can be damaging to your eyes. Vision is a precious thing and you should take care to preserve it. A glance at the sun, especially through a telescope or binoculars can ruin your vision for life. Therefor, take extreme caution when viewing the sun and always consult with an expert.

The ONLY exceptions to the Basic Rule

There are, however; some specific circumstances that would allow you to look at the sun directly - but you must know exactly what you are doing.

The first and most common circumstance is when special filters are in place that block the sun's harmful radiation. These filters should be checked carefully before use and should also come from a reputable supplier. When use, the intense light is reduced to a tiny fraction of normal allowing you to look at the sun. With a solar filter one can see sunspots and other features of the sun. It is strongly advised that you do not do this unless under the direct supervision of an expert in solar observing.

The second circumstance is when a total solar eclipse is taking place. During the brief minutes of a total solar eclipse, the moon gets in the way of the brightest part of the sun making it safe to see other parts of the sun such as the corona, prominences, and chromosphere. You can only look at the sun during totality. Do not look directly at the sun during the partial phases leading up to the total phase. If you are not sure when it is safe to look at the eclipsed sun, ask someone who has been there before to tell you when it is safe. And then look away when instructed to do so.


Projection Viewing

A very safe way to look at the partial phases of a total solar eclipse is to construct a basic pinhole projection. A pinhole projection is the result of light traveling through a small hole and projecting an image of itself against a light colored surface.

You can create a pinhole shield with a piece of paper or cardboard. Poke a hole in paper using a pencil point. The pinhole only needs to be a couple of millimeters across and should be as round as possible. Try not to leave jagged edges if punching the hole through cardboard or some other stiff material.

Pinhole effects can be observed during an eclipse in a variety of places. The shadow through a tree can create a myriad of pinhole images. Loosely woven hats with lots of small holes are a favorite of many eclipse-chasing veterans.

Another interesting technique is to punch several pinholes in the paper so that multiple eclipse images appear on the projected surface. Don't put the holes too close to each other as that will cause the images to overlap.

The projection technique can also be applied to a telescope or binoculars. That is, an image from the eyepiece can be projected to a surface and the sun studied in detail. Someone very knowledgeable about his or her telescope can do this for you and some small telescopes are sold with solar projection attachments. Under no circumstances should you look through the telescope unless directed so by an expert at solar observing (and make sure there is a filter attached in the proper place!).

Another nice feature about using a projection technique is that multiple people can view the eclipsed sun at the same time, safely. The image at left shows the projected sun at the beginning of the eclipse in 1972. A 4.25" telescope had a solar screen attached at the projected point from the eyepiece. This allowed multiple people to see the progress of the eclipse without potential damage to their eyes.

When observing a solar eclipse in a group, projections are often a popular stopping point for those wandering about waiting for totality. It is a great opportunity to meet and talk with other eclipse enthusiasts while keeping track of the lunar shadow progress across the disk of the sun. I have set up projections in the past and have enjoyed showing the sun's disk to many casual observers as well as local people who were curious about our expeditions to see the sun go out.

The safest way to observe the partial phases of an eclipse is by using the projection method. It provides a clear view of the sun and does not risk damage to anyone when handled correctly. I advise practicing with the telescope for those just learning how to observe the sun. During the hour (or more) before totality it provides a very entertaining way to track the eclipse progress and meet other interesting eclipse chasers as well as endear yourself to the local populace.


Solar Filters

There is only one way to observe the sun with a telescope directly. That is with a solar filter. Not any filter will suffice for this sort of viewing. You must get the right filter for your telescope. The best place to start is by contacting the telescope manufacturer to see if they sell a solar filter for your particular telescope. If they don't (or if they offer eyepiece filters only), then contact one of the filter companies listed at the end of this section.

A solar filter deflects (or rejects) a significant amount of the energy from the Sun. There are two ways to accomplish this feat. The first involves a mirror like substance that reflects the light energy and only lets a small amount through. The second is a dark filter that absorbs the energy allowing only a small amount to get through for viewing. Solar observers generally prefer a reflection filter since they will not heat up as much as absorption filters.

The solar filter should be located at the front of the optics and not in between the main objective and the eyepiece. Older telescopes may come with a solar filter that attaches to an eyepiece - do not use these. There is a chance that the filter will crack due to the concentrated heat of the sunlight being focused by the primary lens/mirror to the eyepiece. If they happen to crack, they will no longer serve as an adequate solar filter and could result in eye damage if used.

Viewers are cardboard glasses that allow for naked eye observation of the eclipsing sun. They should NOT be used for cameras, binoculars, and/or telescopes. The filter is typically a MylarŪ sheet.

The image at left shows members of the Columbus Astronomical Society posing for a picture with their solar viewers on after a successful eclipse trip to Germany in 1999.

Do not look through a telescope or binoculars with these filters on. They are meant solely for direct observation of the sun without any additional optics.


Select a Safe Location

Safe Solar Eclipse Observing also involves more than just not looking at the sun. Selecting the right location and locale can be equally important. For example, it is not advised to set up very near to a highway as a driver may loose control during totality attempting to view the eclipse while underway. In the European eclipse of 1999, at least one traffic fatality was reported that was directly attributed to the eclipse. The driver was looking up and not where they were going, and thus ran into a row of parked cars along the side of the highway.

The location where you set up will either greatly enhance or greatly deter from your enjoyment of the eclipse event. If you want to enjoy eclipse then do not set up next to "party people". Some people go to the eclipse strictly for the party atmosphere and this can diminish the enjoyment of someone who is solely interested in observing the phenomena. On the other hand, if you are looking for a party during the eclipse, don't set up next to some "stick in the mud" astronomer intent on ruining your party! Look for others that want to enjoy the eclipse the way you do and you will greatly enjoy it more as your share your common experience after the eclipse is over.

Here are some examples of safe places to observe an eclipse.

At the hotel or resort where you are staying: The biggest advantage of doing this is that you will not have to carry your equipment far or endure a long bus or car ride to the observing site. In addition, if you plan to celebrate the eclipse with a toast or party, the hotel will normally be quite accommodating.

On board a ship: Ship travel (cruising) offers a great way to view the eclipse and enjoy the hospitality of a resort like community. Another advantage with ships is that one does not have to worry about the weather as much since the crew has access to modern navigational tools and meteorological data. Since most eclipses occur over water (3/4 of the Earth is water) at some point or another the ship can maneuver into clear, calm waters and sky conditions that allow you observe the eclipse.

With an organized tour group: Eclipse travel groups are becoming very common these days and you can hitch along with an expert who has scouted out the area and considered many other comfort aspects of the eclipse observing. If you venture out on your own, you may not find a friendly location to set up your telescope let alone additional amenities such as food, something to drink, and a restroom to relieve yourself! The eclipse event last several hours and your enjoyment will be greatly enriched by sharing it with others who are there for the same reason.

Here are some examples of places not recommended for observing an eclipse.

Along the highway: As mentioned before, it can be quite hazardous to simply pull over to the side of the road and set up a telescope. About the only way that will work is if you pull over at a rest area. In addition, that location will have some facilities even though they may be limited.

Near a neighborhood hangout: The locals will undoubtedly come out to see what is going on and if you happen to be setting up, they will come over to see what you are doing. If your intent is to share your knowledge with the locals, this can be wonderful but if you have traveled a long distance, are by yourself, and want to observe the eclipse this may not be a good place.

In a crowd: One again, if your intent is to teach about the sun and the eclipse then setting up in a crowded location can be fun. But if you are after pictures of the eclipse you may not want to be in a place where someone could trip over your tripod or block your view of the sun. In some cases, a crowd cannot be avoided such as on a cruise ship. Under those circumstances it is recommended that you set up in a group of friends or acquaintances that will not disturb your process.

On an animal path: Another place not to set up is on a path normally traveled by animals going in and out at the end or start of a day. That is, unless your plan is to watch the animals and not the eclipse to see what effect the eclipse has on them. There is a story of an eclipse watcher who set up in a chicken coup to get out of the wind. During totality the eclipse chaser did not see much as the chickens all came home to roost for the evening as totality set in. I've also heard about an observer that set up near a lake full of wild birds that took flight during the eclipse blocking the view of the eclipse. Whether these stories are true or not doesn't really matter, the lesson they teach is simple; avoid animal paths and habitats.

Near a war zone: This should be pretty obvious. A war zone can shift directions at any time and stray munitions could get dangerously near. If the country you are visiting is experiencing revolution or terrorist activities to a high degree, it will be a good idea to either avoid that area or to hire your own security to ensure your safety.

There are other considerations when selecting a viewing location. Because most eclipse chasers have brought cameras, are tourists in the area of the eclipse, and many have binoculars or telescopes, they may be prime targets for thieves. Although you cannot really say that anyplace is 100% safe all the time, you should be prudent in selecting a location that will not make you too much of a target.

 

The above information is kindly provided by www.eclipse-chasers.com/safe.htm