Quote:
Originally Posted by Digital_Artist
If the result are basically the same than why would someone buy ASA 8 inch Hyperbolic astrograph,which cost fortune, (apart from motorized focuser, which is needed for fast telescope to focus) instead of GSO 10 or 12 inch newtonian with ASA corrector or any other type of corrector for that matter, which would cost way less?
BTW: ASA parabolic astrograph are also costly.
Thanks in advance.
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In general, the cheaper scopes are mechanically much less well made, which introduces all sorts of alignment problems in a fast scope. If you buy a top end scope you will not have to spend countless hours sorting out problems - you will have paid a premium for someone else to do it. Some of the parabolic coma correctors cannot produce corrected images over the full extent of a very large CCD - ones that can are expensive.
Apart from that, you get bragging rights and a very pretty looking instrument if you buy something like an ASA. You don't get either with a GSO, but it will still work the same if you get it set up right - commercial quality optics are more that adequate for imaging with larger scopes. Top end optics may have spot diagrams that are nice and tight, but for an 8 inch scope, typical atmospheric blur is likely to be maybe 10x the area of the diffraction spot, so it doesn't really matter what the spot diagrams are like (within reason). The main user advantage of high end optics is the assurance that any eventual problems are not likely to be optical.
Joe's advice is good - one of those books would be a good investment