Astronomy

64 ASTRONOMY • MAY 2018

is not as important as it is when
you’re planning to use a CCD
or DSLR through the telescope,
yet this does depend on the
length of the exposure.
Other beneficial accessories
include a reasonable-size mem-
ory card that allows you to
quickly download exposures, a
fully charged battery or an
external power supply, and an
intervalometer. I also carry
spare memory cards and
charged batteries with me.
The intervalometer is an
important accessory. It allows
you to program and control the
length of your exposures with-
out touching the camera, so

that you avoid inducing vibra-

tions that can ruin your expo-

sures. Canon refers to its

intervalometer as a Timer/

Remote Controller; Nikon calls

it a Multi-Function Remote

Cord; and Sony calls it a

Remote Commander. Be cer-

tain you check your camera

model compatibility if you pur-

chase this accessory.

With an intervalometer, you

can set the length of each expo-

sure when you set your camera

to “bulb” on some DSLRs or

“manual” on others. With most

intervalometers, you can set the

time between activation and

when the first exposure is

taken, the period between

exposures, and the number of

exposures. Some intervalom-

eters even allow you to set the

time between mirror lockup

and exposure, since the mirror

lockup introduces vibration in

the system.

Camera settings

Proper camera and lens settings

will not only save you a lot of

frustration, but also noticeably

improve the quality of your

images. And the beauty of digi-

tal media is that you can delete

and reshoot — unless your

subject is a total solar eclipse or

a magnificent fireball.

Turn off the lens autofocus:

Many camera lenses — in your

smartphone, point-and-shoot

camera, and most DSLR lenses

— have a feature called autofo-

cus. For taking general photos

of people and scenery, this is an

invaluable feature, but not so

for astrophotography. If you

leave the camera DSLR lens on

autofocus when taking astro-

nomical images, the lens will

perceive the sky as blank and

continually search for the

focus. Autofocus also drains

your battery.

Turn off your flash: This

one might seem obvious, but

I’ve seen instances when a nov-

ice did not know to turn off the

flash, or an experienced imager

forgot to do so. This is one of

the reasons why I still use a

checklist when I prepare for a

night of astrophotography.

Mirror lockup: This lets

you lock the mirror before you

begin imaging. In normal oper-

ation, when the mirror swings

out of the way as you start an

exposure, the motion intro-

duces a vibration into the sys-

tem. This is not a problem for

normal, handheld, usually

short exposures, but it can

cause problems for exposures

when you want stars to appear

as points of light, rather than

squiggly lines.

Set the white balance

to auto: White balance lets you

adjust colors so that the image

looks natural in its setting.

This is great if you are shooting

a wedding under some unusual

lighting, or skiers against

bright white snow, but it’s

not necessary for nightscapes.

So, leave the white balance

on auto.

ISO setting range: The

measure of the camera sensor’s

sensitivity setting is the ISO, a

photographic standard adopted

during the film days by the

International Organization for

Standardization. Most digital

cameras start at a low sensitiv-

ity of 100 ISO (or even 64 ISO)

and range to 102,400 ISO on

high-end cameras. Although a

high ISO setting would seem

ideal for low-light astronomical

imaging, there is an important

trade-off. As you increase the

ISO, you increase electronic

noise. I prefer to image at a

maximum of 400 ISO. But the

noise-suppression software in

your camera may work won-

ders. Experiment with higher

The LighTrack II Mount

from Fornax is easy to assemble

and use. The company also sells

the optional FMW-200 wedge

and polar alignment scope.

ASTRONOMY: WILLIAM ZUBACK

Celestron’s Advanced VX

Mount has a maximum weight

capacity of 30 pounds (13.6

kilograms). Counterweights

and a tripod are included.

COURTESY OF CELESTRON

The constellations Andromeda and Triangulum (with their two large galaxies)
dominate this wide-field shot taken through a Canon 6D with a 47mm lens
mounted on a Sky-Watcher Star Adventurer tracking mount. JOHN CHUMACK