Sbig CFW8-A User Manual

CFW-8A

Color Filter Wheel

Manual

SBIG - Santa Barbara Instrument Group

©2002 Santa Barbara Instrument Group

147-A Castilian Drive
Santa Barbara, CA 93117
Telephone [phone]
FAX [phone]

Copyright Notice

This manual is copyrighted by Santa Barbara Instrument Group
(SBIG). This manual may not be copied in whole or in part.

CFW-8A Manual
Version 1.4
Printed 2002

©2002 Santa Barbara Instrument Group

147-A Castilian Drive
Santa Barbara, CA 93117
Telephone [phone]
FAX [phone]

TABLE OF CONTENTS

Introduction ...................................................................................................1

Overview of Taking and Processing Color Images.............................2

Telescope Work.....................................................................................2

Color Image Processing......................................................................3

Hardware Reference....................................................................................4

Making the Electrical Connection ...................................................7

Maintenance of the Color Filter Wheel...........................................12

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The CFW-8A Color Filter Wheel

INTRODUCTION

This manual describes Santa Barbara Instrument Group's CFW-8A
Color Filter Wheel. This product can be used with CCDOPS or CCDSoftV5
software to facilitate taking and processing of tri-color images with most
SBIG cameras, including the ST-4X, ST-5, ST-6, ST-7, ST-8, ST-9 and ST-10
Imaging Cameras. This list may be expanded as we add new models. Many
third party software packages also support SBIG products.

The Color Filter Wheel is an accessory that mounts on the front of the
camera. The filter wheel has five filter positions: Red Filter, Green Filter,
Blue Filter, Clear Filter and 1 Clear Aperture position for additional filters of
your choice. "Primary" color images are taken through the Red, Green and
Blue Filters and the Clear Filter allows ordinary observing without having to
refocus.

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Overview of Taking and Processing Color Images

This section provides an overview of the steps necessary, both at
the telescope and in front of the computer, to take and process tri-color
images.

Telescope Work

At the telescope you use the standard CCDOPS software to take
sets of three images for each object. The three images represent the
Red, Green and Blue primary images. Take these images as you
would for monochromatic images except use the filter wheel to select
each of the three primary spectral bands.

You can take equal duration exposures in the Red, Green, or Blue
or match the exposure duration of each primary image to the
brightness of the object. Typical ratios of Red : Green : Blue are 1 : 1 :

1.6 to match the exposure to the CCD's sensitivity although accurate
color balance should be done for your system with neutral grey objects
or "white" G5 type stars.

Each of these images should be dark subtracted1 and should be
saved with a name that indicates the color of the filter (e.g., M51R,
M51G, M51B). Note, however, that different software programs may
handle tri-color files differently and the naming convention you use is
dictated by your software. If you are using a fast system (low F
number) and your images show signs of vignetting (such as a
variation in the sky background level) then you should also take flat

1

You may also want to use the other image enhancement features

of CCDOPS such as removing cool pixels. In general the three

image set should be made to look their best prior to merging the

RGB image.
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