With a total solar eclipse quickly approaching–it’s August 21st–it’s important to know how to protect your eyes in order to safely enjoy the eclipse. It is never safe to look directly at the sun’s rays, even if the sun is partly obscured.

So when you are watching a partial eclipse, you need to wear eclipse glasses at all times if you want to face the sun, or use an alternate indirect method to view the eclipse.

This guideline applies during all solar eclipses, even total eclipses, up until the time when the sun is completely and totally blocked. The short time when the moon completely obscures the sun, known as the period of totality, is the only time when it is safe to look directly at the star.

Eclipse glasses are a popular option, but there are some alternative options as well. Here are three NASA provided safe alternative viewing options that can help you enjoy the solar eclipse:

1. Projection.
This is the safest and most inexpensive way to watch a solar eclipse. You can make a “do it yourself” project out of this by simply placing a pinhole or small opening in a card, holding it between the sun and some sort of screen, like a giant white sheet, a few feet away. An image of the sun will appear on your screen. It can be like watching the eclipse on a movie screen.

2. Filters.
The sun can sometimes be viewed directly when using filters that are specifically designed for that purpose. These kinds of filters usually have a thin layer of aluminum, chromium or silver on their surfaces. One of the most widely available filters for safe viewing is a number 14 or darker welder’s glass. A welding glass that permits you to see the landscape is not safe. Aluminized mylar manufactured specifically for solar observation can also be used. Mylar can easily be cut with scissors and adapted to any kind of box or viewing device. It is crucial that you only use filters that you know have been approved for solar viewing.

3. Telescopes with solar filters.
There are sun-specific telescopes available for sale that are also safe for viewing a partial eclipse. However, these telescopes can be expensive, so many people prefer the alternate options listed above.