https://youtube/watch?v=1_hjaD62DwE&list=UUtHg0Cdx1PQ8xkkvnwGRMUQ A telescope does two things: it collects more light than an eye, so allows one to see fainter (sensitivity), and it increases the amount of detail (resolution) that one can see. https://youtube/watch?v=JtBqsZHCuuw&list=UUtHg0Cdx1PQ8xkkvnwGRMUQ https://youtube/watch?v=1_hjaD62DwE&list=UUtHg0Cdx1PQ8xkkvnwGRMUQ https://youtube/watch?v=YVKolPRUV20&list=UUtHg0Cdx1PQ8xkkvnwGRMUQ Sensitivity is simple: it gets better the bigger you are, so you will always see fainter objects with a bigger telescope: that is why astronomers like to build big things, Resolution is more complicated: the finest detail you will see with a telescope depends mostly on the local atmosphere where you are. This `seeing is caused by turbulence in the air, usually at low levels. There is a typical size to these air-parcels, which is a few inches. At a site with very good seeing the parcels are up to about 10-12 inches, more typically they are 5-6 inches at a good site, 1-3 inches are a poor site, or in bad weather. The air-patches, bubbles, are blown by the wind, so keep changing as seen by one person/telescope, which is why some frames have a lot more detail than do others. most of Southern California - in fact all west-facing ocean coasts - are very good sites, with Mt Wilson and Palomar being famous examples. The effect of this turbulence is that telescopes only see more and more detail until the telescope is larger than the air bubbles. When several bubbles are seen by the telescope at the same time the image no longer improves. When it is windy the bubbles move past quickly, so that the image is changing a lot, and seems fuzzy. That means that larger telescopes do not see more detail. In fact, a good back-yard telescope, well-adjusted, like yours, see just as much detail as a very large professional telescope, like the Palomar 200-inch. Palomar see fainter of course, but no `better. You will get the best possible image quality with a telescope about the same size as the bubbles, with a magnification which is just large enough so that exactly one air bubble is between the telescope aperture and the target image, and with an integration (frame-rate) time such that the bubble doesnt move by more than one-half its size during one film frame. Your technique of `lucky imaging seems to have identified exactly the correct combination of telescope size, magnification and frame rate to match your local atmosphere and wind. From: Gerry Gilmore ([email protected]) Sent: Thu 1/18/0 3:37 AM To: john lenard (santamonicajohn@hotmail) Hello again, and again my congratulations on your superb astrophotography You are clearly getting some images at almost the diffraction limit of your telescope. In the very sharpest images there are hints of diffraction rings visible on the edges of the satellites. That is of course the absolute limit of optical performance, and is only rarely attained. Interestingly, the process you have, of using a high-quality imaging system, with fast read-out, and then selecting the rare `perfect images is something which has been developed and applied somewhat by one of my colleagues here. You might like to look at our local web page presenting some of this: [link to ast.cam.ac.uk] You might also be interested in a journal produced by the MIT Lincoln Laboratory - which is the group which has built some of the things you are seeing. Much of what they do is what used to be the Star wars project, which no doubt involves some of your objects. They dont talk about the military satellites, of course, but there are many dicussions of earth surveillance, and related issues. It is distributed only to academic organisations, so you may need to get your local library to borrow it, but you may be able to get this (for free) from Subscription Coordinator Room L-054 Lincoln Laboratory MIT 244 Wood Street Lexington MA 0240-9185 USA best regards Gerry
Posted on: Mon, 15 Dec 2014 21:23:28 +0000
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