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Photo Forum / Digital Photography / DSLR Cameras / February 2007

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Apochromatic telescope versus telephoto

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RichA - 31 Jan 2007 23:53 GMT
The telephoto was stopped down to f5.6, the telescope is wide open at
f5.9.
The telescope is 388mm while the telephoto is 300mm and the image from
the scope was downsized to
match the telephoto image.  Both are at 100%.  The telescope uses
FPL-53 which is the highest grade of low-dispersion fluoro-glass
hybrid, the Olympus lens was one of the first to incorporate an "ED"
element.
The small apo only cost $300 with a case, a real bargain especially
considering the whole thing is machined METAL
and not a scrap of plastic.

Telephoto:
http://www.pbase.com/andersonrm/image/73775632

Telescope:
http://www.pbase.com/andersonrm/image/73775321

The instruments:
http://www.pbase.com/andersonrm/image/73774867
Charles - 01 Feb 2007 02:28 GMT
>The telephoto was stopped down to f5.6, the telescope is wide open at
>f5.9.
[quoted text clipped - 16 lines]
>The instruments:
>http://www.pbase.com/andersonrm/image/73774867

What was the focal distance for those shots?
RichA - 01 Feb 2007 05:48 GMT
> >The telephoto was stopped down to f5.6, the telescope is wide open at
> >f5.9.
[quoted text clipped - 18 lines]
>
> What was the focal distance for those shots?

About 20ft.
Charles - 01 Feb 2007 06:01 GMT
>> >The telephoto was stopped down to f5.6, the telescope is wide open at
>> >f5.9.
[quoted text clipped - 20 lines]
>
>About 20ft.

Thanks
Andrew Haley - 01 Feb 2007 11:11 GMT
> The telephoto was stopped down to f5.6, the telescope is wide open at
> f5.9.
[quoted text clipped - 7 lines]
> considering the whole thing is machined METAL
> and not a scrap of plastic.

> Telephoto:
> http://www.pbase.com/andersonrm/image/73775632

> Telescope:
> http://www.pbase.com/andersonrm/image/73775321

There are very clear sharpening haloes areound the edge of the text,
but none around the test as shot on the telephoto lens.  I wonder how
a lens causes sharpening haloes.  Perhaps it's an artefact of the
"downsizing".

Andrew.
tomm42 - 01 Feb 2007 14:04 GMT
> The telephoto was stopped down to f5.6, the telescope is wide open at
> f5.9.
[quoted text clipped - 13 lines]
>
> The instruments:http://www.pbase.com/andersonrm/image/73774867

The telescope results are remarkable. But Nikon has had "ED" elements
since the '80s, compare to a Nikon (or Canon) 300f2.8, bet the results
would be much closer. Also both telescope and lenses will do better
closer to infinity focus.  No sharpening would be a better comparison
too.

Tom
eawckyegcy@yahoo.com - 01 Feb 2007 14:50 GMT
On Jan 31, 6:53 pm, "RichA" <rander3...@gmail.com> pulls another turd
out of his a.s:

> [...]

There is a principle in law whose name I have forgotten.  But it goes
something like this:  the prosecution can't cherry-pick within the
evidence, or, similarly, the defense is allowed to submit the
remainder of evidence.  We can see aspects of this being played out in
the current Pickton murder trial in British Columbia, with the jury
having been forced to watch hours and hours of otherwise boring video
of a cop lying to his prisoner to extract a confession;  the
prosecution would surely like to just focus on the few moments of
damning "admissions" and move on, but the defense insists that every
last frame be presented -- or none of it.

And so it is with optical tests.  Here we have a proven nitwit pairing
off an almost 40 year old lens, utterly defunct at this point, with a
modern telescope.  Shock of shocks, the lens has less contrast than
the telescope!  A few moments at google offers a reasonable
explanation:

http://photosig.pcphotoreview.com/mfr/olympus/35mm-primes/PRD_84404_3111crx.aspx

Yes indeed, Rich probably has the non-multicoated version of this
lens.  But even if he had the MC version, what of it?  Maybe instead
of wasting money digging archeological garbage out of the pawn shop,
Rich should be going to Henry's or Vistek and buying modern 300/4
optics to (cough!) "test"?  But even in the unlikely event of a huge
difference in performance, we have the issue that his el-cheapo $300
crap scope is lacking in things like aperture control, auto-focus
motors and the like.  Let's listen in on a conversation somewhere in
Utah:

A: "My BMW is faster than your jeep."
B: "Let's talk about it at the top of Elephant Hill."

Yes, Rich, you are an idiot.  Accept it, embrace it, celebrate it.
But why not in the privacy of your own outhouse, eh?
Craig - 02 Feb 2007 01:00 GMT
Actually the Williams Optics APOs are considered very good small
refractors. Now I'll admit that telescopes don't have apeture control
or Auto-focus, but they don't need them for what they are designed for.
Signature

Remove My_Skin to E-mail me.

> we have the issue that his el-cheapo $300
> crap scope is lacking in things like aperture control, auto-focus
> motors and the like.
Lagonda - 01 Feb 2007 18:32 GMT
> The telephoto was stopped down to f5.6, the telescope is wide open at
> f5.9.
[quoted text clipped - 16 lines]
> The instruments:
> http://www.pbase.com/andersonrm/image/73774867

Uh, that is very nice. Telescopes have this "astronomical note" for
observing. And I think that they are made much better than most of
photo-optics. Oly vs. W. O.?? Hm. Photo lens must be not goog, but veeery
gooood made to have the results as very good APO-scope. :) I wonder, what
would happen if it was some Takahashi or Astro Physics instead W.O.?? :)

:)
 
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