Sky & Telescope - USA (2019-09)

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pVENUS RISING This 8-second exposure recorded through a 35-mm

f/1.4 lens captures the rising central bulge of the Milky Way with bright

Venus refl ecting in the waters of a Chilean fjord.

skyandtelescope.com • SEPTEMBER 2019 37

camera to record the night sky. Other models take per-

fectly pleasing astro-images, and if you desire more pinkish

hydrogen-alpha nebulosity in your images, several vendors

offer affordable services to modify your camera.

Regardless of your camera body, it’s the glass (the lens)

that makes the shot. The stars in night-sky photographs are

points of light that excel at revealing the fl aws of an inferior

lens, by being distorted into elongated blurs or other strange

shapes. Try to buy quality lenses for your camera — you and

your astrophotos will be glad you did. And since you’ll be

shooting at sea where a mist of salty spray might land on

your lens and damage its coatings, pick up a skylight or other

neutral lens fi lter to protect its exposed element.

The focal length of the lenses you use depends on what

astronomical object you want to photograph. Wide-angle

lenses in the 18-to-50-mm range, combined with a full-

frame camera (or 14-to-35-mm range on an APS-format or

“cropped-frame” camera), will capture excellent vistas that

include several constellations, the Milky Way, or dazzling

aurorae in one shot paired with the glittering sea below.

Longer focal lengths are better suited to capturing bright

subjects, particularly solar eclipses (with a proper solar fi lter

during the partial phases) or lunar eclipses.

You’ll want to use as fast a lens as you can get, such as f/2.8

or better, in order to take the shortest exposures to minimize

smearing due to the movement of the ship. Be aware that lens

prices get pretty steep on high-quality, fast-focal-ratio lenses,

though you can often fi nd good prices on the used market.

The Moon and planets are very small in wide-angle pho-

tos, and you really need a long telephoto lens — at least 300

mm — to start to resolve craters. But high-resolution images

of the Moon and planets are better left to your time on land.

After all, you can capture them from virtually any place on

Earth, whereas dark skies often require travelling great dis-

tances for many of us.

Still, the planets will reveal their respective brightnesses

and colors in wide-angle shots, which can be very beauti-

ful when combined with the Moon or a few constellations

over the open sea. A nifty trick is to photograph the Moon

or planets when they are rising or setting above the sea and

capture their refl ected light on the water. If you’re lucky

enough to have the Milky Way in the frame — well, it doesn’t

get much better than that!

Imagers on a limited budget may prefer a multi-purpose

lens to serve both daylight and night photography needs. I

recommend a good 28-to-300-mm zoom lens. These lenses

combine a moderately wide fi eld to get those Milky Way

shots, with enough magnifi cation to pull in details on the

qOCEAN OBSERVATORY Left: The open ocean is perhaps an unlikely destination for photographing the night sky, but cruise ships can get you to

clear, wide-open skies in a way you may not have considered before. Right: It’s often best to avoid shooting from the main deck, where lights from the

recreational facilities overwhelm everything but the Sun and Moon.