Hi,
Found this on Pnet (1999) about the Orion Mak 500. Perhaps it really is F8.
Perhaps someone knows how to calculate the true aperture and thus DOF.
May have to try one of these things.
Mike
Chuck Norcutt wrote:
> This reminds me that I have an Orion 500mm f/5.6 mirror lens/spotting
> scope that I've almost never used......
> so maybe I'll give this lens a whirl again. At f/5.6 I may actually be
> able to focus it.
>
I sure hope so, because DOF is going to be 'interesting'.
I think all those 500-600/8 lenses are f8 not just because of size and
cost, but for DOF reasons.
Have fun and let us know, maybe even, gasp, post some samples. :-)
Moose
"It's a longer focal length, isn't as fast, but it's a proven design. May or
may not suit your needs. BTW, if the MAK-500 is a 90mm lens, and has a focal
length of 500mm, how can it be an f/5.6??? You see, it has a central
obstruction, so it's light gathering is less than a 90mm lens. Marketing did
the math, but engineering should have applied a correction factor. It's
probably closer to f/8 in terms of actual light gathering. With TTL metering it
probably doesn't matter, but I think it's a bit deceptive. OTOH, everybody does
it. Also, consider the solar filter. In spite of its optical problems, I really
enjoy using my Meade to look at sunspots. We're near the peak of the solar
cycle right now. Good luck!
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