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Thanks guys, that was pretty much what I needed to know.
Better prepared is always good when you a forced to catalogue shop (Tassie, doncha know?).
Hadn't really considered the Spher. Aberration problem in these 'cheaper' scopes, but had i given it a bit more thought then... Makes sense since they use almost the full objective edge to edge.
Camera lens makers avoid this somewhat by reducing the effective aperture on their cheaper lines so they can use a lesser quality objective etc. and concentrate the imaging on the centre of the glass, thus avoiding the poorer edge quality. You most often see this in primes where the edge glass is hidden behind a thick bezel.
I am puzzled given the knowledge of optics we have obtained, and the manufacturing and grinding standards we have achieved, that we still have problems in 'branded' products. I wonder what extra it would cost to lift this 102 for example to a consistent standard minus the spherical aberration etc.
Anyway, enough musings. Thanks for the valuable information.
Hope you all have a nice and happy festive season.
Trevor
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