Essentially, it's the ultimate photo challenge. On August 21st, photographers across the continental United States – and especially photographers within a 70-mile-wide band stretching from Oregon to South Carolina – will have no more than 160 seconds to get the shot of a lifetime.

Starting around 9am PT, the moon will pass in front of the sun, and a large swath of North America will be treated to a total eclipse. And if you ask anybody who knows anything about astronomy, it is a huge deal. Dr. Tyler Nordgren is such a man. He's a professor of physics and astronomy, an award-winning photographer and a self-described Night Sky Ambassador. Here's how he puts it:

"Half the people that are alive right now weren’t even alive the last time something like this was visible from the continental US. Secondly, there are 12 million people just living in the path of totality that are going to get the chance to see it, so it will be the most-viewed total solar eclipse probably in history."

The most seen, most photographed, most shared, most tweeted – potentially the most people in total are going to be able to experience this in one form or another

Given that just about everyone in its path will have a camera in their pocket, he says it's also likely to be the most photographed in history.

"The most seen, most photographed, most shared, most tweeted – potentially the most people in total are going to be able to experience this in one form or another."

Hungary – My first eclipse photo that I took in 1999 superimposed on the stamp I bought there comemorating the eclipse by showing its path across the country. Photo and caption by Tyler Nordgren

But unless you're a seasoned landscape photographer or astrophotographer, Dr. Nordgren thinks you might be better off not photographing it at all and just enjoying the view. He quotes Warren De la Rue, a pioneer of astrophotography. After becoming the first person to photograph a total eclipse "he wrote in his journal afterwards, that if he ever got the chance to see another one, he hoped to be able to see it without any equipment at all."

In short, "See your first eclipse, photograph your second." But if you're unconvinced, Dr. Nordgren does have some advice.

Get ready

Preparation is key. Remember – 160 seconds. Of course, you'll want a tripod and a cable release to lock everything down and minimize shake.

"If you really must photograph this, you’re going to want to practice a whole bunch of techniques in the weeks leading up so it’s as second nature as absolutely possible during those precious seconds."

Protecting your eyesight and your gear is equally important. It's only safe to point your eyes or your camera sensor directly at the sun during totality – a little bit before or after and you're risking serious damage. He suggests a pair of solar eclipse glasses and a filter for your lens. Per NASA, your glasses should meet the ISO 12312-2 international standard.

Be sure to use both during partial phases of the eclipse – you risk damaging your eyesight, not to mention your camera, with just a pair of glasses and an unfiltered lens. Crucially, don't forget to take off the filter during totality. You'll be extremely disappointed with the results if you don't.

Lensrentals recently posted a useful article detailing some specific settings to dial in if you plan on using a longer lens.

Pick a lens

What kind of lens should you use? Well, not surprisingly, it all depends on what you're going for. If you want the sun as your main subject, you'll obviously want a longer lens. "To really capture big detail in the corona and the object itself, you'll want a lens with a focal length of around 500mm; between 400 and 600mm at least."

But don't forget that a total eclipse also presents a unique landscape photo opportunity. If you'd rather capture the eerie effect on the scene, a wider lens will produce excellent results too. It's all a matter of personal preference.

Star Flyer – the 2013 eclipse as seen from the deck of a four-masted sailing ship racing across the Atlantic. Totality was 42 seconds long and I was on a quickly moving (and rocking) surface. Photo and caption by Tyler Nordgren

No matter what kind of shot you're going for, you can size things up ahead of time by photographing a full moon.

"Something to keep in mind is that during totality the sun turns black, and is surrounded by this ghostly corona, so the spectacle of the object itself is this black disk with this white glow around it. That black disk is the size of the full moon, so take whatever your camera equipment is, take whatever your lens is and go out and photograph the next full moon. See if whatever size dot that appears. If that’s interesting to you, then great – that’s the lens to use."

Get thee to the path of totality

If you're set on photographing the eclipse and have the safety and gear requirements nailed down, all that's left to do is get yourself into the path of totality for the big moment. Easy enough, right? Well, unless you're lucky enough to live there, or you started planning your eclipse vacation years ago, chances are extremely slim that you'll be able to find a campsite or hotel room in the path at this point. Your best bet is to find accommodations within a reasonable driving distance and set out as early as possible.

Ideally, you also want to aim for somewhere that's less likely to have cloud cover. Dr. Nordgren knows all too well what a cloudy eclipse view looks like.

"If you’re going to do the close up photograph, you could be almost anywhere provided you’ve got clear skies. But I’ve also seen some really spectacular photos of totality through wispy clouds that give this dramatic view as well... just as long as you’re within that path of totality and the cloud cover is not so total that you’re utterly blacked out. And I’ve had that happen."

This is the partial phase just a minute or two before totality in the Faroe Islands. Those clouds totally socked us all in 30 seconds before totality so we saw nothing. Photo and caption by Tyler Nordgren

If you're hoping to get a wider shot, then great news: this eclipse will cross some of the most beautiful locations in the continental US. Provided you can get there, you can pretty much take your pick of landscapes. "What do you find compelling? Is it a hardwood forest like the Great Smoky Mountains, is it the big jagged peaks of the wind river range in Wyoming? Or being along the Oregon coast? It's up to the photographer."

And really, that's what makes this such an incredible event.

"Everywhere from rocky shorelines in Oregon to snowcapped volcanic peaks in the Cascade range, to the deserts of Idaho and the mountains of Wyoming, the farmlands of Nebraska, the hardwood forests and the Mississippi river... you really have the entire breadth, literally, of the United States of America to capture this in."

160 seconds – that is not a lot of time to see what I think is the most awe-inspiring, unnatural, natural experience in nature

Whether or not you can get to the path of totality, and whether or not you choose to photograph the event, you'll still be treated to an amazing array of photos and videos from photographers across the US. And unless you're dead set on photographing it, consider leaving the camera at home.

"If you haven’t seen a total solar eclipse, I encourage you, don’t waste your time photographing it. Chances are, somebody else will get a better photo. But if you are that kind of expert photographer, practice so that you can set your camera up and let it do its thing with as little input as possible, because 160 seconds – that is not a lot of time to see what I think is the most awe-inspiring, unnatural, natural experience in nature."