Of course, at this extreme focal length we have to use a telescope, in this case a C14 at prime focus. But at this image scale, chasing high resolution, we run into major headaches with tracking accuracy and the problems of poor seeing. Despite mirror lock-up, even shutter shudder restricts the range of useful subexposures. Long exposures, a minute or longer, do not record shutter shudder but lead to over-exposed stars, bloated further by seeing. Exposures under one second but longer than, say, 1/30th second (depends on the solidity of the mount) add little tails to all the stars from shutter shudder. Nevertheless, it is possible, with sufficient determination, to image the brighter DSOs at very high resolution, through the use of very short exposures, or a combination of short and long. The inset shows a 1:1 crop from a stack of 4 second exposures, demonstrating that it is indeed possible to resolve the Trapezium stars from A to the H doublet (a pair of Mag 15 stars separated by a mere 1.6 arc-seconds under the glare of the main Trapezium stars blazing away at up to Mag 5).
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