SBIG

More Information Price $149.00 Weight 6 oz. Warranty 2 years

There are two parts to the adapter. One is the adapter body itself. It has a Canon bayonet mount that duplicates the front of a Canon camera body. Your Canon FD lens attaches to this bayonet. The second part is a T-thread insert in the adapter body that threads into the T-thread ring on the front of your SBIG CCD camera. The T-thread ring on the CCD camera normally holds the camera’s nosepiece (which must be unthreaded from the camera before use).

There are two sets of three set screws on the CLA-7 to fine-tune the focus of the adapter. The rear set holds the T-thread insert in place in the adapter body. It allows you to thread the insert in or out to fine-tune the back focus of the lens to match the distance reading on the lens or reach infinity focus. The front set allows you to set the rotational orientation of the lens so that the f/number and focus distance marking scales are at an easily readable orientation.

The self-guiding chip in the CCD camera will show as a black area in the image with wide open fast focal ratio/short focal length lenses (for example, a 50mm lens used at f/1.2). The vignetting problem disappears if the lens is stopped down to f/4 or f/5.6. SBIG recommends stopping down your camera lens to f/5.6 when used with the CLA-7, which has the added benefit of reducing the uncorrected spherical aberration that most lenses have at fast f/numbers (which can lead to halos around bright stars if not corrected by stopping down the lens).

The CLA-7 cannot be used with a color filter wheel, as the camera lens will not be able to reach infinity focus with the filter wheel in place. It can be used with the male-to-male t-thread adapter (#MMTC) in place of the threaded barrel to hold a 1.25" filter behind the camera lens. This can be useful for taking wide field H-alpha images, for example.