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Re: [MeadeUncensored] 2" ep query

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  • schmityuk
    Thanks Guys for the tips, in particular John for detailed answer regarding the size of the rear cell. Yeah, premium eps don t come cheap Mark, not to mention
    Message 1 of 5 , Nov 1, 2004
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      Thanks Guys for the tips, in particular John for detailed answer
      regarding the size of the rear cell. Yeah, premium eps don't come
      cheap Mark, not to mention all the filters I've build up over the
      years for 1.25 eps!

      Thanks again

      Ed
      UK



      --- In Meade-Uncensored@yahoogroups.com, Christopher Erickson
      <cerickson@g...> wrote:
      > And don't forget the University Optics widefield Konigs as well as
      > the Pentax wide field eyepieces.
      >
      > -Christopher Erickson
      >
      >
      > > -----Original Message-----
      > > From: Mark de Regt [mailto:deregt@e...]
      > > Sent: Sunday, October 31, 2004 8:22 AM
      > > To: Meade-Uncensored@yahoogroups.com
      > > Subject: RE: [MeadeUncensored] 2" ep query
      > >
      > >
      > >
      > > The only thing I would add to John's fine answer is that
      the "premium"
      > > eyepieces, such as Naglers, Panoptics and the Meade SWA and
      > > UWA eyepieces,
      > > have better optics, generally, than the plossls you may
      > > already have. I am
      > > quite impressed with the higher quality of the viewing with
      better
      > > eyepieces, whether wide-angle for something like M42, or high
      > > magnification
      > > for planets with something like the Nagler 3-6mm zoom. The
      > > problem with the
      > > premium eyepieces, of course, is the rather hefty prices some of
      them
      > > command.
      > >
      > > Mark de Regt
      > > Redmond, Washington, USA
      > > 47.7 N. Latitude; 122 West Longitude
      > > Astro Images: http://www.de-regt.com/Astronomy
      > >
      > >
      > > -----Original Message-----
      > > From: John Mahony [mailto:jmmahony@y...]
      > > Sent: Sunday, October 31, 2004 1:05 AM
      > > To: Meade-Uncensored@yahoogroups.com
      > > Subject: Re: [MeadeUncensored] 2" ep query
      > >
      > >
      > >
      > > --- schmityuk <e.casey@n...> wrote:
      > > >
      > > > Hi all, I've recently moved up to a 12"GPS from a 8"SC. My
      query
      > > > regards 2" eps. Would I gain a great deal from investing in a
      bunch
      > > > of 2" eps over my existing 1.25's that I have built up for my
      8"
      > > > scope? Logic would suggest that this advantage is only
      relevant to
      > > > increased field of view as I would expect high power planetary
      > > > viewing would be the same for the 1.25 or the 2", is that a
      correct
      > > > assumption?
      > >
      > > Right. The scope's primary/secondary focuses an image at the
      > > back of the
      > > scope
      > > (put some scotch tape over the rear opening amd you can focus
      > > the moon on
      > > it,
      > > with no EP), and the EP is just a magnifying glass to view
      > > this image. The
      > > barrel of a 1.25" EP limits the view to a 1.25" (at most) part
      of this
      > > focused
      > > image, but that's plenty for planets. 2" is only needed when
      > > a very large
      > > _true_ field is desired.
      > >
      > > > Could I get exactly the same effects with the right
      > > > combo of f/ls etc with a 1.25" setup?
      > >
      > > If you use a 6.3 focal reducer, you can get the same view you
      > > could with 2"
      > > EPs, assuming you view through the standard rear port. But
      there is a
      > > better
      > > alternative. The standard rear port inside diameter is only
      1.5", so,
      > > roughly
      > > speaking, you can get only 1.5" of true field through it,
      > > which limits the
      > > advantage of 2" EPs. The reducer lens is also only about
      > > 1.5", so you can
      > > get
      > > essentially the same view through it with 1.25" EPs (the
      > > reducer lens will
      > > "condense" the 1.5" field down to a size suitable for 1.25"
      > > EPs). On your
      > > 8",
      > > the baffle tube is also only 1.5" ID, but on your 12", the
      > > baffle tube is
      > > much
      > > larger, so the rear port can be unscrewed to reveal a larger
      opening.
      > > Astro-physics sells a $60 adapter that screws to the larger
      > > opening, and
      > > accepts 2" accessories, so you can use 2" EPs and get a full
      > > 2" true field.
      > >
      > > To use this adapter, you need a 2" "refractor style" diagonal
      > > (the type with
      > > a
      > > 2" barrel in front. There are 2" diagonals designed to screw
      > > straight onto
      > > the
      > > standard rear port of an SCT, but then the true field is
      > > limited to ~1.5".
      > >
      > > -John
      > >
      > >
      > >
      > >
      > >
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