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@REPLYADDR RichA <rander3128@gmail.com>
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On Saturday, 23 September 2023 at 21:05:40 UTC-4, Alan Browne wrote:
> On 2023-09-23 19:14, RichA wrote:
> > May also be good for astrophotographers, but I`d need to see
100% images to be sure. Price is right and considerably less than Borg,
William Optics (which I suggested to them 20 years ago) and Omegon
offerings of similar type.
> >
https://petapixel.com/2023/09/22/ttartisans-new-500mm-f-6-3-full-frame-mirrorles
s-lens-is-just-329/
> Not sure how one gets to "Large Aperture" claims with an f/6.3 lens...
>
> --
> "Markets can remain irrational longer than your can remain solvent."
> - John Maynard Keynes.
In astronomy, anything faster than f.7 is fast, and f/2.8 is
virtually non-existent. For whatever reason, astronomers don`t use high-end (not
many) telephoto lenses, preferring to loose a couple stops and use
telescopes. i presume cross sensor correction in camera lenses isn`t good
enough, but I`ve yet to see any real comparisons between top end telescopes
used as lenses (Takahashi FSQ-106 which is a fast scope with 4 inch
aperture) or top-end modern telephotos.
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