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An Istar 8" F8 ( ?) Achro lens went cheap here on IIS Trade not too long ago for well under $1000 - the glass was substandard and showed veins of inhomogeneity that could be seen in the extra focal star test, so you would have to be vigilant. The cost of optical glass skyrockets as you go larger as the cost of finding glass and value of pieces free of inclusions and veins goes up exponentially .
I'm interested in doing some more lens work sometime, and would like to do a large achromat ( F12) - I was thinking about something in 10" league . But something like that would have to go into a very large dome or use at least one folding flat to cut the tube down to something manageable and then you would have to look down from the top.
I think such a configuration would not tick the 'romance' box which I think is the great appeal of achro refractors which are basically visual instruments.
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