| An
Introduction |
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Video Astronomy is perhaps the easiest and most affordable method
of solar, lunar and planetary imaging around today. In fact, several new cameras available
today have onboard image integration capabilities and are so highly sensitive they are
being used to image deep sky subjects without the aid of a military grade image
intensifier. Advanced CCD technology and market demand has substantially reduced
manufacturer costs thus making this wonderfully simple recording medium more readily
available to the average consumer. Even the common computer webcam is being modified for
use at the telescope by amateurs around the world. |
| The heart of
modern video cameras is the CCD chip mounted on a small printed circuit board which also
contains all the processing circuitry to make it a complete video camera. Low-cost
off-the-shelf C-mount cameras are also available in convenient pre-fabricated enclosures.
Most are based on automatic circuits offering little user controllability however some do
offer adjustable functions. If you're a do-it-yourself person, then assembling a low cost
and light weight camera of your own is a simple and rewarding project and you'll be amazed
at the results. |
Saturn was captured using a surveillance based
B&W video camera (see below) and coloured filters.
|
| These days there
are a number of commercially available systems designed specifically for use at the
telescope. The Astrovid 2000 (now redundant) supplied by Adirondack Video Astronomy is one such
camera that provides complete user control flexibility. Video can be considered a
convenient medium resolution imaging tool. The images in these pages are purely an example
of what can be achieved when capturing targets of the solar system and the deep sky. Click
Here to see a list of video animations
Below: Jupiter
and Saturn in February and March 2005 - 254mm (10-inch) Newtonian RGB filters
and GEM-I security video camera. Processed with Registax and Photoshop.
|
| Applications: Conventional video cameras are short exposure devices and as such have
(until recently) been best suited for imaging the brightest celestial subjects like the
Sun, Moon, planets and meteors etc. When using common low light security cameras without
onboard frame integration and special software, faint fuzzy objects such as nebula and
galaxies reveal little detail unless the camera is coupled to an image intensifier as
mentioned earlier. But these standard cameras can reveal more than is visible on a noisy
monitor by applying software such as (AstroVideo) by COAA. This software essentially sums hundreds or even
thousands of individual video images producing a highly improved signal to noise image and
revealing extended structure that appears to be invisible when viewing the monitor in
real-time. Deimos in June 2001 captured using
AstroVideo.. |
Mars captured using the Astrovid 2000 video
camera at f/36 on a 24-inch Cassegrain and colour filters. Note the less than natural
pinkish appearance is is due to the fact no IR blocking filter was used.
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| [Top] Extreme Video
Astronomy |
|
| As mentioned
previously, until recently common low light security cameras were only suitable for
imaging the brighter celestial targets. Faint deepsky targets required the use of
expensive image intensifiers like those used by the military. Obtaining images with
inexpensive video from light polluted suburban sites like the M42 image at right was
nothing short of fantasy a few years ago. Several amateurs have experimented quite
successfully with modified (cooled) webcams combined with image stacking software in
recent years to produce similar results. I like to refer to this type of astro-videography
as 'extreme video astronomy' since the technology is now so advanced and the results so
remarkable. |
NGC 1566
|
| The new range a
of highly sensitive Sony image sensors (CCD's) have made this all possible. Similar CCD's
are also now being produced by other semi-conductor manufacturers including Panasonic. |
| The GSTAR - EX camera is a highly
sensitive, low light camera utilising the Sony Super HAD ExView image sensor. The camera facilitates on board frame integration
from x2, x4, x8, x12, x16, x24, x36, x64, x96, x128. In x 128 mode the screen is refreshed
once every 2.6 seconds. The camera also features on screen display with several other
functions including signal gain and shutter speed controls. |
|
| The results are
amazing! Even during normal video operation (integration mode switched off) I could see
nebulosity about the trapezium stars in the Orion nebula. A far more expensive camera is
the compact Watec 120N. Claimed to be the most sensitive video camera available to amateur
astronomers today, it offers long exposure times up to 10.24 seconds but is riddled with
hot pixels and cannot be set for shutter speeds faster than 1/50th of a second. |
| This was taken
from suburban Sydney while the light from a gibbous Moon was scattered through thin haze
in the atmosphere. Under such conditions I certainly wasn't expecting to see such results.
Taken at prime focus with a 250mm
f/5 Newtonian, these images were acquired using the 128X frame accumulation mode of the GSTAR - EX camera with True
Technology RGB filters. A dark frame of the same exposure setting has been subtracted to
remove hot pixels.
[Top] |
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| |
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Recording images:
This can be achieved in two ways: Directly
to video tape (Digital (DV), Beta or SVHS quality is recommended) or via a computer fitted
with a video frame capture device. A modified webcam can also be used to create wonderful
images and with the convenience of plug-and-play USB port connection.
Advantages
of Video for Astronomical Imaging:
During moments of poor seeing (most
apparent when using higher powers), single snap shot pictures can be blurred or distorted
due to local and high atmospheric air turbulence.
|
| Capturing objects
as a stream of pictures with a computer in media file AVI movie format (or similar) or to
videotape allows the user to replay the sequence frame by frame until the image presenting
the least distortion appears. This frame can then be stored as a single image using image
capture software. Aside from the technical benefits, video is an extremely cost effective
imaging medium within the budgetary reach of most amateur astronomers. |
| [Top] Processing Images:
For digital imagers, the computer has become
as much an essential tool as the telescope itself. With raw (single) video images, video
noise (a speckled appearance) is apparent in each still frame captured. This is
particularly the case with images captured from paused videotape. Software tools such as
Adobe PhotoShop, Ulead's Photo Editor or PaintShop Pro are excellent commonly available
programs for processing images. These programs enable the user to stack several of the
best images in order to reduce the background (thermal) noise with layering tools and also
offer several other processing filters for improving feature contrast.
Capturing Video to the PC
I use my own software AstroAVI
which records all my equipment and site information along with dates and times and the
target object details in a convenient database for later reference while digitising images
from video or directly from a camera.
Image Selection Software
Eyeballing the sharpest images in a video
sequence is still the most efficient method for best results. For selecting the best
captured video frames I use VirtualDub
which is far more enjoyable to use than the option list style of frame selection and
deselecting provided in the programs below. I then import the exported VirtualDub images
as bitmap files into one of the programs listed below.
Stacking Images and Dark Frame
Subtraction
A couple of automated image stacking tools I
use and highly recommend are:
Registax
(Highly Recommended)
K3CCD Tools (Very Good)
If you want to try creating colour images
with a black and white video camera then you'll need to use Red, Green and Blue light
filters such as the RGB
Dichroic filter set from True Technology. Using
one of the aforementioned software packages, you can then apply the resulting monochrome
image from each corresponding filter to the appropriate colour channel of an RGB 24 bit
image to create a colour picture.
[Top]
Further Information:
There are a number of very good video
astronomy related resources available on the internet. I have listed a few below:
My
Astro Shop : Australian dealer for the GSTAR - EX Deep Sky and Planetary
camera
Steve Quirk's GSTAR-EX pages Some outstanding results from a 12-inch
and 8-inch scope from a good dark sky location.
Modern Astronomy : - A commercial site offering a host of dedicated
products, information and customer picture gallery.
Adirondack Video Astronomy:- A commercial site offering a host of
dedicated products, information and customer picture gallery.
VideoAstro:-
A dedicated email discussion group on the subject of Video Astronomy The group share their
experiences, images and ideas. This group have been highly successful in attracting many
newcomers to the hobby.
Jim Ferreira
(DeepSky Video Imaging)
VideoAstronomy.org
QCUAIG:- Is a U.K. based discussion group mainly centred around
adapted PC desktop style cameras for use in astronomical imaging. They feature images
taken using the COAA
Astrovideo software
|
| Books |
| I have seven
published astronomy books in press from 3 publishers including Sky Publishing (USA), New
Holland Publishers and Springer (USA). They range from advanced to intermediate and the
young readers. |
| Video Astronomy guide |
Video
Astronomy
BAA Reader Review
TWCAC Review
Planetary Society
Hardin Optical
AS&T
|
The original
 |
Revised Edition
Best Price in Oz at
Australian Sky & Telescope
|
| Introductory
guide to observing the Solar System |
The Night Sky
Second Edition
An introductory guide to observing
the Sun, Moon & Planets.
Top Australian seller now
in its 2nd EDITION
Buy
from my Astro Shop
[Top] |
more info...
|
2nd EDITION
|
| A
pocket guide to observing the Moon |
Exploring the Moon
An introductory guide to
observing
our closest celestial neighbour.
Sold throughout Australia, New Zealand,South Africa and the U.S
Buy
from my Astro Shop
[Top] |
|
 TASCO
EDITION |
A guide to our universe |
Atlas
of the
Southern Night SkyA
comprehensive and easy-to-use reference guide for southern hemisphere star gazers.
Includes constellation maps with deep sky objects, lunar maps, guides to planetary
observing, astrophotography,
image processing and more.
Steve Massey & Steve Quirk
Hard Back 290 pages |
|
| How
does the night sky work?
An easy-to-read introduction to the
wonders of our universe for all
young enquiring minds.
Hard Back
[Top]
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| Space,
Stars & Planets
A large illustrated guide for young people
into the wonders of our universe.
Hard Back |
 |
| Deep
Sky Video Astronomy An in
depth guide to the wonderful world of modern video CCD technology and how it is used to
image faint deep sky targets with basic telescopes from the backyard. Plus in-depth image
processing procedures to get the best out of your video images.
Steve Massey & Steve Quirk
Soft Cover |
draft cover - due April 2009 |
