CCD Image of a Double Star
ST-4 CCD Image of Double Star SAO 74295
photo by Thea Dravecz
The double star system SAO 74295 is of visual magnitude 5.5, which makes it too faint to be seen with the unaided eye from the telescope platform at Moravian College. The two components of the pair are separated by only 4.4 arc seconds, so separating the individual stars provides an excellent test of the resolving power of a telescope system. The slightly inclined line through the image is shown also as a graph of light intensity. Notice that two peaks can clearly be seen on the graph, whereas the image lacks the detail in the central regions of each star of the pair. The CCD camera used was an SBIG ST-4. It was mounted on an 8-inch Meade LX-200 telescope on the roof of Collier Hall of Science.
The Moon's apparent diameter from the Earth is approximately one-half degree, which is 30 arc minutes, or 1800 arc seconds. The two stars above, resolved at a separation of only 4.4 arc seconds, can be compared to the more familiar Moon to get an idea of the resolutions possible from this observing site and with the equipment available.