Re: Eyepieces, filters, and such


"mlimber" <mlimber@xxxxxxxxx> wrote in message
news:1137793625.546530.10130@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Jan Owen wrote:
> > "mlimber" <mlimber@xxxxxxxxx> wrote in message
> > news:1137791462.549061.178980@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > Thanks for the suggestion. My eyepieces are indeed 1.25".
> > >
> > > The page you mention sounds a little scary when it makes claims like
> > > this: "Amazingly, when a major publication tested what was purported
to
> > > be a new planetary ocular, our orthos were not included in the
> > > comparison test. Well, I think by now everyone is familiar with the
> > > term 'media bias.' We have been fighting it for years and years."
> > >
> > > And this: "My long personal relationship with the owner assures that
we
> > > receive only the best of the best." (What if the owner and UOptics
get
> > > into a tiff over something? Will they then sell substandard optics?)
> > >
> > > Is University Optics trustworthy and are their products high
quality?
> > > Is there really a bias against them?
> > >
> > > Cheers! --M
> >
> > I've been dealing with Jan Seyfried (who IS University Optics) for
over 25
> > years.
> >
> > I have MANY eyepieces, most of which are MUCH more expensive. They
all
> > were purchased to do specific jobs. For lunar/planetary work, the UO
Abbe
> > Orthos are indeed quite good (consequently, I have the complete set).
You
> > can pay a LOT more, and the improvement, if any, will be subtle
indeed...
> >
> > Ignore the hyperbole... If you think that's bad, look at a Meade ad.
And
> > I can show you some from, say, VernonScope of yore that would stand
your
> > HAIR on end.
> >
> > Performance is what you are looking for, and University optics WILL
> > deliver, provided you are OK with the two caveats I mentioned.
>
> Ok, thanks. As far as the caveats, I only have experience with two
> telescopes -- the Newtonian reflective Celestron that I mentioned and a
> refractive Bushnell (it's my father-in-law's and I'm not sure of the
> model number, but this one looks like it:
> <http://www.bushnell.com/products/telescope/specs/78-9470.cfm>). I find
> the field of view and eye relief of the former to be significantly
> better than the latter. How do you think the UO eyepieces would
> compare?
>
> What about getting a Barlow lens to improve the magnification of my
> existing lenses? Also, I read in the archives that the 4mm eyepiece
> from the Celestron accessory kit is next to useless and certainly can't
> be used with the Barlow. Would that hold true on my Celestron
> telescope? Would the same be true of the UO 4mm and 5mm eyepieces? (It
> seems that a 5mm + Barlow would give me the maximum useful
> magnification of my scope.)
>
> Cheers! --M
>

A 2X Barlow and a 5mm Ortho would indeed take your scope to it's maximum
rule of thumb magnification. So a 4mm eyepiece with Barlow would deliver
a dim, and probably somewhat fuzzy image.

You might find you like the image quality better with a 6 or 7mm Ortho and
a Barlow (a little brighter and a little sharper). And make sure, if you
go the Barlow route, to get a GOOD one...

As for your comments about field of view and eye relief between a Bushnell
scope and the Celestron scope, the field of view is a function of the
apparent field of the eyepiece AND the focal length of the scope, so two
different scopes of different focal ratios, with different eyepieces,
delivering images at different magnifications will deliver images with
different actual fields. Once you are at the same magnification, the
actual field will be a function of the field stop diameter of the
individual eyepiece. So you really can't compare them unless you are at
the same magnification with both scopes.

And eye relief has nothing at all to do with the telescope. It is
entirely a function of the eyepiece. It is how close you have to get to
the eyepiece with your eye in order to take in the whole field all the way
out to the field stop. The scope you have the eyepiece in doesn't matter
in this case, as long as it is functional...

--
Jan Owen

To reach me directly, remove the Z, if one appears in my e-mail address...
Latitude: 33.6
Longitude: -112.3


.

Relevant Pages

  • Re: Tal 2m or Explorer 150/200?
    ... The scope seems to bear some ... The eyepiece screws,should make no difference to the focussing. ... > observing but the chaps at Telescope House stillreckoned it would ... > tempting to push the magnification beyond the 10mm Plossl and 2x Barlow ...
    (uk.sci.astronomy)
  • Re: true magnification of Televue 3x?
    ... do have the JMI installed between the scope and the Televue, ... image scale was smaller than with the 3x barlow. ... Powermate 5x (and thereby get less overall magnification once the filter ... these are effectively complete 'scope' assemblies used to ...
    (sci.astro.amateur)
  • Re: Eyepiece Question
    ... Viewing planets at high magnification is always a crapshoot. ... There are many considerations when viewing planets with a telescope. ... why I can't get the same clarity as I get with the 26mm eyepiece. ... the scope to its optical limits. ...
    (sci.astro.amateur)
  • Re: Need help setting up my TASCO Telescope
    ... I think this one is a 525X scope when using the 3X extender with 4mm ... to the 1.5X erecting eyepiece or the 3X Barlow before the "skeeters" ... eyepiece and Barlow or other devices, the _useful_ magnification is ... This is why telescopes advertised by power, ...
    (sci.astro.amateur)
  • Re: Need help setting up my TASCO Telescope
    ... to the 1.5X erecting eyepiece or the 3X Barlow before the "skeeters" ... That seems to be the scope I have. ... eyepiece and Barlow or other devices, the _useful_ magnification is ... This is why telescopes advertised by power, ...
    (sci.astro.amateur)