How To ~

CCD Basics

Mounting the CFW-8 to the SBIG ST-7

By Matt Oltersdorf
August 1999

SBIG ST-7 CCD camera &
            CFW-8 color filter wheel
click to enlarge

    In this tutorial I will lead you through the process of permanently attaching your SBIG ST-7 CCD camera and CFW-8 color filter wheel.  The color filter wheel can be used without permanently attaching it to the CCD camera but you will find it easier to attach to your telescope if the CCD and CFW are permanently attached to each other.

    The Color Filter Wheel is an accessory that mounts on the front of the CCD camera, and allows users to take images through optical filters.  The CFW-8 filter wheel has 5 filter positions: red filter, green filter, blue filter, clear filter and 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.

    Ordinarily the CFW-8 is installed onto the camera using the T-thread and mount.  If a more permanent mounting of the CFW-8 to the ST-7 is desired, the filter wheel can be mounted directly to the ST-7 front plate as follows:

1. Remove the ST-7's T-thread mount (held in place with 4 phillips head screws).  This will reveal the ccd chip which is a Kodak KAF0400. 

Remove the ST-7's
                      T-thread mountT-thread mount removed,
                      revealing ccd chip and self-guide chip


2. Remove the cover of the CFW-8 and pull the filter magazine out of the housing.

removed front cover of
                    CFW-8remove the filter magazine

3. Remove the 4 rubber hole plugs from the rear of the CFW-8 by pushing them through the housing with a small allen tool or an ink pens works well also. 

remove the 4 rubber hole


4. Using the two 4-40 x 5/16 cap screws and the two 4-40 x 5/16 phillips head screws attach the CFW-8 to the
                      front of the ST-7CFW-8 attached to the
                      front of the ST-7provided, attach the CFW-8 to the front of the ST-7.  The 2 phillips head screws go in the holes near the center of the filter wheel and the 2 cap screws go in the holes near the outer radius of the CFW-8.  Make sure you use the provided screws whose length of 5/16 is required to thread into the ST-7 front plate without breaking through the blind taps.

5. The CFW-8 has a cable that comes out the side that needs to connect to your camera electronics.  The CFW-8 gets its power and positioning information fromphone-jack connector
                      that allows you to connect to the telescope for
                      tracking and self-guidingconnect the CFW-8 cable
                      to the 9-pin camera portthe camera thru this connector.  The cable plugs into the ST-7's 9-pin telescope connector adjacent to the cable connecting the ST-7 to the PC.  Additionally, the CFW-8 connector has a phone-jack connector that allows you to connect to the telescope for tracking and self-guiding.

    This is the S.B.I.G. recommended procedure for permanently connecting the CFW-8 color filter wheel and the ST-7 CCD camera.

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