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Re: Newbie - Barlow Question

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  • John Bambury
    ... was ... aware of ... sell. I ... ignorance) ... that I ... meant I ... deep ... 3x to ... next ... -- ... a ... focal ... a ... that ... Pentax ...
    Message 1 of 23 , Oct 1, 2004
      --- In skyquest-telescopes@yahoogroups.com, "Charlie Stout"
      <cstout@h...> wrote:
      > Thanks for the response John. When I bought the Klee I got to speak
      > with Mr Seyfried. He basically said the same thing, that the Klee
      was
      > actually meant to work with his UO Orthoscopic line. I wasn't
      aware of
      > the narrow field issue. My plan is to use the Klee with my existing
      > eyepieces, then maybe pick up a couple of the ortho's that they
      sell. I
      > really want this for planetary/lunar work and I know the UO line of
      > orthoscopics will be good for that.
      >
      > The main reason I chose the Klee was (and obviously with some
      ignorance)
      > that it is 2.8x not just 2x. It was the only higher power barlow
      that I
      > have seen that compares to the plus/ultima lines. For me that
      meant I
      > could pick up the ortho EP's in the 18 to 9mm range and get a nice
      deep
      > view without the extreme tiny exit pupils. Are there high quality
      3x to
      > 5x barlows out there?
      >
      > By the way the moon looked great at 589x through my 5.7mm/2.8x klee
      > combo. I was pleasantly surprised by my humble XT6. I'm hoping my
      next
      > views of saturn and jupiter can take some high powers.
      >
      > Charlie
      >
      >
      >
      > --- In skyquest-telescopes@yahoogroups.com, cstout@h... wrote:
      > > Just great. Does that mean that it will work with all 19mm and
      > lower EPs?
      > >
      > > Charlie
      > >
      > > ------------------------------------------------------------------
      --
      > --------
      > > --------------------------------------------------------
      > > Charlie,
      > >
      > > The University Optics Klee Barlow has serious vignetting issues
      > with
      > > longer focal length widefiled eyepieces, significantly worse than
      a
      > > short barlow in fact. You will not notice this with short focal
      > > length eyepieces but it may well be very apparent with longer
      focal
      > > length eyepieces. This occurs because the Klee only has 19mm of
      > > clear aperture compared to a normal 1.25" barlow of top quality
      > which
      > > has normally over 25mm of clear aperture. The Orion Shorty Plus
      > has
      > > a clear aperture of 27mm but the extra aperture is offset a little
      > by
      > > the steeper light cone. The Klee barlow has very sharp clear
      > optics
      > > as do just about all products from UO but you need to keep the
      > > vignetting issue in mind when choosing the eyepieces to combine
      > with
      > > it.
      > >
      > > Clear Skies
      > > John Bambury
      >
      >
      > >Charlie,
      >
      > Don't Panic !!!!
      >
      > Its not quite as simple as that. Picture the Klee barlow as being
      a
      > bit like a short drinking straw compared to a normal barlow being
      > more like an empty cardboard toilet roll due to its larger clear
      > aperture. The UO Klee is a very short barlow, somewhat shorter than
      > the Orion Shorty Plus/Celestron Ultima so you have a very short
      > barlow combined with a very narrow clear aperture.
      >
      > If you stick to barlowing shorter focal length eyepieces (<20mm fl)
      > and particularly those that don't have an ultra wide FOV, you
      > possibly won't have a problem and won't detect a difference. Then
      > again you could. Each eyepiece/barlow combination can be a law unto
      > itself. The two combinations where you are most likely to notice
      > vignetting are with the longer focal length eyepieces and those
      that
      > have a wide apparent FOV. The types of eyepieces that may not work
      > so well in that barlow are things like the 24mm Panoptic, 20mm
      Pentax
      > XW, 22mm Panoptic, 19mm Panoptic, 16mm Nagler T5 and various plossl
      > or orthoscopic designs with a focal length from 20mm to 40mm. What
      > you "could" notice with these eyepieces is a darkening of the
      > entire field as you go further away from the center of the FOV,
      > particularly in the outer 20%. I don't know that its a major
      concern,
      > just depends on the eyepieces you are likely to use. As I said in
      my
      > previous post the UO Klee barlow provides top quality images on
      axis
      > with excellent light transmission, when used with eyepieces that do
      > not cause vignetting, regardless of any vignetting the on axis
      images
      > are still very good. I wouldn't lose a lot of sleep over it, but
      then
      > again if you asked me prior to buying the barlow should I buy the
      > Klee? My answer would have been, there are better barlows
      available
      > for a similar price including the Shorty Plus/Celestron Ultima. On
      > the other hand I also know several experienced observers who own
      the
      > Klee and like it.
      >
      > Clear Skies
      > John Bambury
      >


      Charlie,

      Televue make a 2.5x Powermate and it is a quality product as is their
      3X barlow, both are more expensive than the UO Klee. I have a full
      set of UO HD orthos which I use for planetary viewing and also 4
      Pentax XW's which I prefer to use on DSO's. I still prefer the HD
      orthos on moon and planets notwithstanding the tight eye-relief and
      narrower FOV. If you plan to use the HD orthos up to 18mm or the
      standard orthos with your Klee barlow you probably will never see a
      problem with it as the eyepieces only have a 45 deg AFOV.

      Clear Skies
      John Bambury
    • donaudy
      ... Charlie, I love my XT6 too, but please don t expect to run power that high on the planets. I ve been to around 500x for fun on the moon as well, but even
      Message 2 of 23 , Oct 1, 2004
        --- In skyquest-telescopes@yahoogroups.com, "Charlie Stout" <cstout@h...> wrote:
        >> By the way the moon looked great at 589x through my 5.7mm/2.8x klee
        > combo. I was pleasantly surprised by my humble XT6. I'm hoping my next
        > views of saturn and jupiter can take some high powers.
        >
        > Charlie
        >

        Charlie,

        I love my XT6 too, but please don't expect to run power that high on the planets. I've
        been to around 500x for fun on the moon as well, but even in extrodinary seeing, you
        won't get sharp detail on Jupiter or Saturn over 250x. I have had some fun sessions on
        Saturn at 300x, but there's no detail advantage at that power over 240x or so, it's just neat
        to see the bigger image. I've never had a night where Jupiter takes 300x without
        breakdown and I'm blessed with good seeing fairly regularly here. If you can run in the
        200x-240x range on Jupiter, you'll be doing great and you'll also see a whole bunch of
        detail at that power, and even less. But I agree with you that the humble XT6 is
        surprising. Mine has clearly shown the Cassini Division at only 40x, though not often.

        As far as good Barlows in the 3x and 5x range, TeleVue is certainly one way to go. The TV
        3x Barlow is excellent (I've compared it directly with the Klee and there are no issues with
        the TV unit), and the 2.5x and 5x Powermates are, in the eyes of many, simply the best
        "image amplifiers" available.

        Best,
        Clyde
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