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Re: I give up

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  • ubergroovin
    ... Yeah I gathered that, but I decided to let that slide and roll it off my shoulder. And I agree, I was thinking about the N8i, the N8GPS (on a good wedge
    Message 1 of 52 , Apr 30, 2005
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      --- In telescopes@yahoogroups.com, "John Bambury" <jbambury@b...> wrote:

      >
      >
      > I didn't call the ASGT mount garbage, I was referring to your
      > statement. Matched to the correct scope the ASGT mount does a very
      > good job IMO, but its not as good as the Nexstar 8 GPS.
      >
      > Clear Skies
      > John Bambury

      Yeah I gathered that, but I decided to let that slide and roll it off
      my shoulder.

      And I agree, I was thinking about the N8i, the N8GPS (on a good wedge
      and with the heavy duty tripod) would perform better than the ASGT, but
      at more than 2x the price!

      ASGT can handle 8" SCT just fine... wait till ya see the results I will
      get on film with the Hardin 8"f4 (when I get it finally) on my orion
      SVP mount, which is as you know, in the similar class as the ASGT, but
      with even smaller tripod legs, and no autoguide capability.

      Keith
    • ubergroovin
      I never thought of it as divided camps... Exposure time is determined by f ratio, and image scale is determined by focal length. To not think of both at the
      Message 52 of 52 , May 2, 2005
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        I never thought of it as divided camps... Exposure time is
        determined by f ratio, and image scale is determined by focal length.

        To not think of both at the same time is alien to me, it is just a
        fact of photography. Focal length and image scale need to be
        considered in how stable you need to be (how accurate your guiding
        needs to be in astrophotography), and the converse is, the focal
        ratio needs to be considering when factoring the exposure time. I do
        not expect my Nikkor 200mm f4 to show the same image as an 8"f4
        reflector, but I do expect the same target to have the same density
        at the same time exposure, but obviously the image scale is bigger
        with the 8"f4, since it has an 800mm FL vs 200mm FL. It is just a
        given to me to think of both.

        now MONEY can BUY not having to think about f ratio... just have
        enough MONEY to buy CCD cameras that are sensitive enough to work
        with f12 scopes, and you get the best of both worlds. For the non
        gaziollionares out there, we are stuck with using faster scopes, and
        the more image scale we want, the bigger our scopes, and hence
        mounts, need to be. 8"f4 is about as big as I can personally afford
        at this time.

        Keith

        in telescopes@yahoogroups.com, "Kevin Dixon" <ksbtk@c...> wrote:
        > Hi Joe:
        >
        > This is one of those topics where there never is agreement among
        all
        > astrophotographers. Some are in the camp of the f/ratio; others
        are in the
        > camp of focal length. I have seen discussion threads on this topic
        go for
        > weeks, each side presenting compelling arguments for their position.
        >
        > I personally approach imaging with film and CCD cameras from the
        standpoint
        > of emphasis on focal length because it takes into account f/ratio
        and
        > aperture, whereas the reverse is not necessarily true. It is also
        how I
        > judge the demands on a mount. The longer the focal length, the
        greater the
        > demand placed upon the capability of the mount. And that is
        generally
        > without influence from f/ratio.
        >
        > To be sure, there will always be disagreement on this topic. And,
        I don't
        > pretend to understand the complex math and physics behind it.
        Based on my
        > personal experience, and on the experience of those I hold in the
        highest of
        > regard in the fields of astrophotography and CCD imaging, we
        worship
        > together at the altar of focal length.
        >
        > Clear as mud now Joe? <g>.
        >
        > Clear skies,
        > Kevin
        > www.kevindixon.westhost.com
        >
        > From: "Joe Fittipaldi" <j.fittipaldi@b...>
        >
        >
        > > ---- Kevin Dixon <ksbtk@c...> wrote:
        >
        > >>And to be more accurate, it really is not the focal ratio that
        should be
        > >>emphasized but, rather, focal length, when it comes to
        > >>astrophotography/imaging.
        > >
        > > Hi Kevin,
        > >
        > > as a start I'm not an astrophotographer, although, I have taken
        the odd
        > > picture of the sun (using a filter) and moon by holding the
        camera to the
        > > eyepiece.
        > >
        > > You statement above directly contradicts what Stef Cancelli said
        in his
        > > post about astrophotography, he stated that the F ratio should be
        > > emphasised not the focal length or aperture.
        > >
        > > Something doesn't add up, have I missread or missunderstood any
        of the
        > > statements made?
        > >
        > > I know you are an accomplished astrophotographer, could you
        please explain
        > > to me what is the most important aspect between f/ratio,
        f/length,
        > > aperture?
        > >
        > > Regards
        > >
        > > Joe.
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