There is Still Time to Get a Solar Eclipse Lens and Filter!

Approximately once every 18 months (on average) a total solar eclipse is visible from some place on the Earth’s surface. However, the average duration between solar eclipses that are visible from any specific location on earth is roughly 375 years. If you live in the U.S. and miss the upcoming opportunity on August 21, 2017 to see the total solar eclipse, you won't have another opportunity until April 8, 2024 when the path goes from Texas to Maine. And if you miss that one, your next two chances will occur in August 2044 and 2045.

In other words, the upcoming total solar eclipse is so rare that you have few opportunities in your lifetime to see (and photograph) the event in North America. Don't wait! Prepare for the solar eclipse today.

Here's a list of suggested gear for photographing the event:

As to which telephoto lens you should choose, that depends on how large you want the sun to be in your frame. Generally speaking, the longer the focal length, the better. Below you can see how the sun will appear at various full-frame focal lengths.

Sun at Various Full-Frame Focal Lengths.gif

A couple of things to keep in mind:

During totality, you won't be photographing the sun, you'll be photoraphing the sun's corona, so the area of the frame taken up by the sun's corona will be larger than what is shown above.
With APS-C sensor cameras, you need to multiply your lens's focal length by 1.6 to get the full-frame equivalent focal length.

There are several great options in regards to long focal length lenses, including the following 400mm+ lenses: