Stars, Milky Way, String Lake, Grand Teton NP

Starry night sky and Milky Way over String Lake and Tetons, Grand Teton National Park. The second mountain to the right of the Milky Way is the Grand Teton. The trees silhouetted in front of the stars are new lodgepines mixed with charred pines from a forest fire 30 years ago. Please visit my photostream every Thursday to see a new ''NightScape'' image. Read the Huffington Post story about my NightScape photography.

See the awe-inspiring NightScape VIDEO – with one Milky Way after another!

''NightScape'' series style: If I only wanted to capture the stars against a totally black sky and have no landscape features in the foreground, I'd just attach my camera and lens to an astronomy type tracking motor, and expose as long as I wanted (using low ISOs). However, doing this would blur the landscape features, because camera would be following the stars and the rotation of the earth! My goal in this series is to show the stars in a relationship to an earthly landscape feature, and not just do astrophotography.

In my style of "NightScape" photography, I am trying to capture the stars as points of light, not star trails, so my exposure must be very short -- usually less than 30 seconds. This requires very fast and expensive lenses and extremely high ISOs. (The Canon EOS 5D Mark II and Mark III are some of the best cameras out there for producing a minimum amount of noise at these high ISOs.)

TECHNICAL STUFF
Camera and Lens: This photo was taken with my 15mm full-frame Canon fisheye lens (30 seconds @ f2.8, ISO 6400). This lens gives me almost a 180-degree angle of view. Many of my photos are taken with the Canon 24mm f1.4 lens (84-degree angle view). I would roughly calculate that the full-frame sensor of my Canon EOS 5D Mark II is about 40 times more sensitive to light than a typical point-n-shoot camera, and several times more sensitive than your eye, when coupled with a 15 to 30-second time exposure. Each exposure is 30 seconds or less (any longer than this, then the stars appear to move or streak, due to the rotation of the earth -- producing star trails or arcs, rather than round dots). Please note that most DSLR cameras with a "fast" prime lens can capture my style of NightScapes.

Fast Lenses: The aperture (or "F" stop) is usually set as near to wide open as the lens design will allow, in order to capture as much light as I can during the exposure time. Prime lenses (not zoom lenses), with large apertures (f2.8, f2.0, or f1.4) are preferred for this type of photography, although I've seen some great images with slower, f3.5 lenses.

High ISOs: Most of my star photos are are taken at ISO 3200, 6400, or 8000. With these high ISOs and fast lenses, the camera is able to see detail that your eye and other cameras cannot. Cameras like mine and Nikon's D3 can go even higher (12800, 25600, 51200, and 102400 ISO), but there is always a trade-off in quality. At the moment, I have chosen not to go above 8000, until I can find technology that will obtain the quality I desire. Some DSLR cameras do not go above ISO 1600. I have seen some exposures with these cameras at that ISO, using an f3.5 lens that look great -- the night skies are a little darker than the ones I shoot (eliminating the fainter stars), but the views are still stunning.

Digital Noise: High ISO's and long exposures (anything over 1-second) can produce digital noise -- what film users call "grain" or graininess. Many cameras (especially point-n-shoot cameras) cannot go above ISO 1600 -- and even their 1600 has more noise (digital graininess) than my 6400. Some have been critical of the noise; however, the noise I'm getting at ISO 6400 right now is less than what film gave me at ISO 800, 10 years ago. It is also much less than what I was getting only 6 years ago at ISO 1600 with any digital camera. Technology has come a long way, and I'm very grateful for all the improvements. It allows me to see what my naked eye cannot! Still, anytime I can lower my ISO to 3200 or 1600, I try to do so, in order to reduce noise. This can be done by "stacking" several under-exposures (taken at ISO 1600), and processing them into one photo, with a brighter exposure.

Narrow window of opportunity: The big problem in doing star photography is finding a totally dark and cloudless sky: It must be at least 2 hours after sunset, at least 2 hours before sunrise; and the moon must have set (because it washes out the stars). A New moon or a less than 8% crescent is acceptable. I rely a lot on moon tables from the Farmer's Almanac. As you can tell, there is only a narrow window to shoot these kind of photos, and it only happens a few days each month (when you add the weather factor).

Light pollution: Oh, and did I mention you must be at least 75 miles from the lights of a large town? There are getting to be fewer of these places on the earth. Some of the glow in the sky, right around the tree line, is from the town of Jackson, WY (population of about 9,000), which is about 20 miles away.

Longer focal length lenses require shorter exposure times: With my 180-degree, full frame fisheye lens I can expose as long as 30 seconds and keep the stars as points (unless the image is enlarge over 12 x 18, upon which the stars appear a little elliptical). A 24mm (84-degree angle coverage) requires that I shorten my exposure to 19 seconds or less. A normal 50mm lenses (45-degree angle coverage) requires a 9 seconds or less exposure! This is because the longer focal length lenses are enlarging the area of the sky you see and magnifying the earth's movement -- requiring even shorter exposure times. Some astro-photographers use the "600 rule" for determining the length of their exposure time: dividing 600 by the focal length of the lens (using a full-frame 35mm equivalent). I adjust this to my own "450 rule", which produces less blurring on larger prints. Thus, the maximum exposure time for a 28mm lens would be 16 seconds (450 / 28 = 16).

Lens technical problems: The bigger my lens' aperture, the shorter I can expose my images, and the lower I can set my ISO. One of my favorite large-aperture lenses is the Canon EF 24mm f1.4L II. However, "big" aperture lenses cost a premium, and I've found that unless I stop down at least one aperture stop or more, the coma (spherical aberration) at the edge of my images is terrible -- the starry points of light grow ghostly wings and take the shape of an obtuse triangle. I am constantly fighting a choice between getting more light to the camera's sensor (by opening up the aperture) or whether I should have better quality (less aberrations) near the edges of my images!

Behind the scenes: The NightScape Story

Explore - #330 for Sept 7, 2011 - Thanks everyone! (What is Explore? How do I get Explored?)
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