Make sure you've got the right specs on your camera
DSLR cameras make it easy for you to adjust the ISO (sensitivity to light), shutter speed, and f-stops, with digital menus on the viewing screen that let you select the settings.
Gilman recommends keeping your ISO relatively low, between about 200 to 400. Put the f-stop (which controls how much light your camera allows in) between f/5.6 and f/8. Then he recommends starting with a shutter speed of 1/2000th of a second -- a tiny window, suitable during maximum light -- and working your way down to longer exposures at 1/30th and 1/15th as the light dims.
“Depending where you are in that moment of totality, the exposure changes a lot,” he says. “You’ll have more or less light to deal with, and it will vary widely based on where you are and what that moment is. So take a lot of pictures, and try to change exposure value while keeping the image consistent.” He suggests using faster shutter speeds if you’re not in the line of totality, to get good images of the crescent.
Put your camera in manual mode
“We want to be in control,” says Gilman. “This event is a short amount of time, and we don’t wanna just go out there pressing buttons and letting the camera decide what our exposure value is.” So how does one regain complete control of how their camera shoots? Put in in manual mode.
Gilman stresses that bracketing -- taking the same image with different shutter speeds -- is the best way to get a good image, since it will give you the opportunity to let different amounts of light into the camera at different times.
Use a tripod
Anyone who’s photographed in low light knows that as steady as you think your hand might be, images can blur, even at fast shutter speeds. The best way to overcome this is with a tripod. It also ensures you’re getting the same image from the same place when you bracket.