Quote:
Originally Posted by ausastronomer
I have two 10"/F5 'ish telescopes. One is a 10"/F5 tubed dobsonian with a GSO mirror (which is very good) and the other is a 10"/F5.3 SDM truss dobsonian with a Mark Suchting mirror. Once the scopes have cooled properly they will both pull 500X plus under favourable conditions, on their ear.
Cheers,
John B
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Sounds like you got lucky with the GSO , John . The point is that an individually crafted mirror ( hopefully) alleviates any doubt about the mirror quality. Mass produced mirrors are a bit of a lucky dip- more so on the larger sizes.
There is also the long term advantage of having a well annealed piece of Pyrex rather than a coarse annealed glass similar in expansion coefficient to plate glass.