Sky and Telescope - March 2016 - 70

Video Observing

SHARING THE VIEW With the addition of a
large TV or monitor, astrovideo cameras let you
share the view with groups of observers.

the AGC and Gamma settings to make
it easier to see and center your target in
the field of view. Next, adjust the Brightness and Contrast to bring out the most
detail possible without overexposing the
brightest parts of the object. You might
need to increase your exposure to find the
best settings for your system. If the video
image displays elongated stars, try reduc-

ing the Exposure and raise the AGC setting to compensate. However, too high an
AGC setting may result in objectionable
amp glow and noise; too low a Gamma
setting might produce a background sky
that's too bright.
If you have very dark skies or can
utilize long exposures, you'll generally
see less noise with a low AGC setting and
the Gamma at 1. However, cameras with
frame integration should be used with
Stacking set for 5 frames and AGC on
in order to activate the stacking process.
Once again, take successive images with
increasing exposure times until you
obtain the best possible image. When satisfied, adjust the White Balance settings
to obtain a pleasing color.
Getting the best image with a reasonable exposure time is a matter of tradeoffs that will vary with sky conditions,
telescope, focal length, and the presence
or absence of fi lters. Once you're happy
with the image, you can hop from one
DSO to another and use the same set-

Pixel Count & Pixel Size

CURTIS MACCHIONI (2)

How can deep-sky video cameras produce
recognizable pictures of galaxies in 10
seconds when a DSLR camera would need
a minute or more? It's partly a matter of
pixel size. The bigger the pixels on the
light sensor, the more light falls on each
pixel in a given exposure and the better
the low-light sensitivity.

Point-and-shoot cameras are poor
choices for deep-sky photography because
they have tiny sensors (to keep their zoom
lenses compact) divided into huge numbers of pixels - which is largely a marketing gimmick. A full-page photograph
reproduced in this magazine needs just 6
to 8 megapixels.
DSLRs have about the same pixel count
as point-and-shoots, but their sensors are
much bigger. That makes each pixel bigger, giving the camera very good sensitivity when operating in low-light levels.
The sensors in deep-sky video cameras
are small, but they have very low pixel
counts. That results in larger pixels, making them extremely sensitive to faint light,
but at the cost of resolution.
-Tony Flanders

VERSATILE CAMERAS Observing with an astrovideo camera like the one shown here
doesn't require much additional equipment to tow into the field. Besides the camera, you'll
need a DC power source and a video monitor or a laptop computer to display your exposures. You can also use a variety of Barlows and focal reducers to tailor your field of view
to each target, just like switching eyepieces when visually observing.

70

March 2016 sky & telescope

tings, varying only the exposure time. If
you prefer to keep the Exposure short,
use higher AGC and lower Gamma values. On the other hand, longer Exposure
provides the most detailed images with
the least noisy backgrounds.
While video won't produce the smooth
backgrounds and subtle detail seen in
dedicated long-exposure astrophotographs, you'll be pleasantly surprised at
how fast and easy it is to obtain spectacular views of galaxies, nebulae, and star
clusters. With a modest-size scope and a
color astrovideo camera, you'll see color
in bright nebulae like M8, dust lanes and
star-forming regions in nearby galaxies
like M33 and M31, and the central star
in M57, the Ring Nebula. And as you get
more involved in deep-sky observing with
astrovideo cameras, chances are your eyepieces may soon begin collecting dust. ✦
Curtis Macchioni enjoys video-enhanced
observing from the San Francisco Bay area.
Visit his website at californiaskys.com.

Typical Camera Sensor
Chip & Pixel Sizes
Point-and-shoot
12 megapixels

Deep-Sky Video Chip
0.4 megapixels

Normal "APS-C" DSLR - 13.5 megapixels

Chips are enlarged 250%
Each small square represents 250 x 250 pixels


http://www.californiaskys.com

Sky and Telescope - March 2016

Table of Contents for the Digital Edition of Sky and Telescope - March 2016

Contents
Sky and Telescope - March 2016 - Cover1
Sky and Telescope - March 2016 - Cover2
Sky and Telescope - March 2016 - 1
Sky and Telescope - March 2016 - Contents
Sky and Telescope - March 2016 - 3
Sky and Telescope - March 2016 - A
Sky and Telescope - March 2016 - B
Sky and Telescope - March 2016 - 4
Sky and Telescope - March 2016 - 5
Sky and Telescope - March 2016 - 6
Sky and Telescope - March 2016 - 7
Sky and Telescope - March 2016 - 8
Sky and Telescope - March 2016 - 9
Sky and Telescope - March 2016 - 10
Sky and Telescope - March 2016 - 11
Sky and Telescope - March 2016 - 12
Sky and Telescope - March 2016 - 13
Sky and Telescope - March 2016 - 14
Sky and Telescope - March 2016 - 15
Sky and Telescope - March 2016 - 16
Sky and Telescope - March 2016 - 17
Sky and Telescope - March 2016 - 18
Sky and Telescope - March 2016 - 19
Sky and Telescope - March 2016 - 20
Sky and Telescope - March 2016 - 21
Sky and Telescope - March 2016 - 22
Sky and Telescope - March 2016 - 23
Sky and Telescope - March 2016 - 24
Sky and Telescope - March 2016 - 25
Sky and Telescope - March 2016 - 26
Sky and Telescope - March 2016 - 27
Sky and Telescope - March 2016 - 28
Sky and Telescope - March 2016 - 29
Sky and Telescope - March 2016 - 30
Sky and Telescope - March 2016 - 31
Sky and Telescope - March 2016 - 32
Sky and Telescope - March 2016 - 33
Sky and Telescope - March 2016 - 34
Sky and Telescope - March 2016 - 35
Sky and Telescope - March 2016 - 36
Sky and Telescope - March 2016 - 37
Sky and Telescope - March 2016 - 38
Sky and Telescope - March 2016 - 39
Sky and Telescope - March 2016 - 40
Sky and Telescope - March 2016 - 41
Sky and Telescope - March 2016 - 42
Sky and Telescope - March 2016 - 43
Sky and Telescope - March 2016 - 44
Sky and Telescope - March 2016 - 45
Sky and Telescope - March 2016 - 46
Sky and Telescope - March 2016 - 47
Sky and Telescope - March 2016 - 48
Sky and Telescope - March 2016 - 49
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Sky and Telescope - March 2016 - 84
Sky and Telescope - March 2016 - Cover3
Sky and Telescope - March 2016 - Cover4
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