Core of Hercules cluster @ f14.6. For comparison, the right hand image was taken with a 10" SCT @ f6.3 with a 9µ pixel CCD camera. Note that this image does not show any more stars even though the f-stop is more than twice as fast and the overall exposure was 5 times longer.
Image may not be used or reproduced without written permission from Roland Christen, Astro-Physics. Copyright 2001