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Re: 100mm f/8 or 130mm f/6

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  • ronbee77
    ... wonder how stopping a 152 down to 100mm would improve the 152? I wonder what it would ... experimentation and testing in ... guessing) on average, a .975
    Message 1 of 45 , Dec 3, 2003
      --- In tmboptical@yahoogroups.com, "W. Gondella" <strehl985@c...> > I
      wonder how stopping a 152 down to 100mm would improve the 152? I
      wonder what it would
      > do to the strehl intensity? Tom, have you ever done any
      experimentation and testing in
      > this regard? This would imply a telescope starting with (I'm
      guessing) on average, a .975
      > strehl, then stopped down from f/ 7.9 to f/ 12! A 100mm f/12 TMB!
      And I would think it
      > would HAVE TO improve the wavefront to *some* degree!!! :) You
      are limiting the area
      > (and errors within) to a much smaller degree (only 43.28% of the
      original surface). This
      > might (totally guessing again) bring a .975 scope up to .98 or
      (dare I say :) .985 strehl?
      > Could we tell the difference? Tom, what say you?
      > WayneG

      Most interesting question, Wayne, especially the last one. The way
      I understand it is that Strehl greater than 0.95, it would be
      extremely difficult if not impossible for the eyeball to see any
      difference, would it not?

      Ron B[ee]
    • W. Gondella
      ... From: leonard_bel To: Sent: Monday, December 08, 2003 2:00 PM Subject: [tmboptical] Re: 100mm f/8 or
      Message 45 of 45 , Dec 8, 2003
        ----- Original Message -----
        From: "leonard_bel" <ngc7789@...>
        To: <tmboptical@yahoogroups.com>
        Sent: Monday, December 08, 2003 2:00 PM
        Subject: [tmboptical] Re: 100mm f/8 or 130mm f/6

        > Wayne ,
        > In your well educated eyes the XL is now first generation ,
        > kind of old in the eyepiece development market now days.

        WG: Perhaps. But so are a lot of my own eyepieces. Most of my Naglers are 1st
        generation (in fact, some of the first made), as are some of my other wide-fields and
        plossls. In fact, I have military surplus, very long Rini eyepieces, and a lot of other
        ones, including an Ortho (no name) I bought ($5.00?) at a swap meet. I judge (and keep)
        an eyepiece based solely on what it delivers to my eye. I may keep an old surplus
        eyepiece but pass on a shiny new "Type 7" with 11 elements (you get the idea). I don't
        discriminate based on price, looks, or name.

        > Some people among us cannot ever hope to purchase a top of
        > the line scope much less a lot of fancy eyepieces to go with it.

        WG: I think everyone has within their reach the possibility of owning at least one good
        quality telescope, if they shop around. And I do not find an unbreakable correlation
        between the fanciness of an eyepiece and the quality of the views it delivers. Lots of
        money and lots of elements WILL get you a super wide, sharp AFOV, but, surely the
        super-mono is based on a very old design--- nothing truly "fancy" about them, and yet they
        have knocked over some of the very best eyepieces out there. I have a 2-inch Kellner
        (60mm) which I have stunned people with. I crank it up to a 15mm (4X Powermate) in my C14
        and after they say, "Wow!" looking at craters on the Moon, I tell them they just looked
        through a Kellner! :) Good eyepieces come in all sizes and shapes. And it depends on
        what you expect out of them and how you use them (and for what).

        > One
        > very long time observer (over 40 years)I know never owned anything
        > other than a run of the mill scope and some decent kellners and
        > ortho's but viewed more and saw more than most people ever will. And
        > after looking through AP scopes ,TV's etc. still enjoyed his equipment .
        > But he did know how to collimate and take care of his scope.
        > Leonard

        WG: Good point, Leonard. While it doesn't hurt to have good equipment, the ultimate tool
        is the OBSERVER himself (or herself). No amount of money spent can make up for raw,
        native observing skill. I see more and more people today getting into this hobby and
        going right out first thing and buying the most expensive stuff available, just because
        they can afford it. Maybe it is because there is (IMO) more equipment, better quality and
        greater affordability, than ever before? I just read where a guy bought his first
        refractor, and it was a state-of-the-art apochromat (non-TMB). I read where some people
        have only been in the hobby for a couple of years (or less?) and own lots of scopes or
        even several A-P's, Questars, Zambuto mirrors, and the like. My first six or so scopes
        (when I was much younger :) were cheap Tascos, Astroscans, and the like! I started out
        with many a Huygens, Ramsden and Kellner-type eyepieces! So I wonder when people now jump
        into the hobby and buy ultra high-end stuff right off the bat whether they ever really
        know and fully appreciate what they truly have?

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