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Thread: UO abbe orthos?

  1. #1
    shawn o'deal's Avatar
    shawn o'deal Guest

    Default UO abbe orthos?

    I have been thinking about getting a really good planetary high power
    eyepiece for some time.
    My current collection is rather hodgepodge, 10 and 25 Orion Sirius plossl,
    15 Orion Expanse, 40 Celestron Omni plossl, 20 kellner (cheap eyepiece but
    rather good views). I don't really mind having a rather small view as the
    ortho's have, as the contrast and views are considered so superb. I am
    looking for as much contrast and detail as possible. The question is, how
    small can I go, or rather what is the best balance for my scopes...
    As far as barlows, I use a Celestron Omni 2x. Would like to get a UO 2.8x
    Klee at some day.
    I have a 120mm Orion Skyview Pro achromat refractor and have a Orion ED80
    apo refractor on order. I am wondering, the 12.5 or the 9 UO ortho? Or you
    have a better idea?
    You all have been a great help since I started on this quest, and I am
    having a lot of fun...

  2. #2
    Michael A. Covington's Avatar
    Michael A. Covington Guest

    Default UO abbe orthos?

    What is the f-ratio of your telescope?

    I hear nothing but good things about University Optics orthos. The eye
    relief is too short for me, so I prefer to use more modern designs, but the
    orthos are undeniably sharp and low-priced.

  3. #3
    shawn o'deal's Avatar
    shawn o'deal Guest

    Default UO abbe orthos?

    f ratios would be 8.3 for the 120mm and the ed80 is 7.5

    "Michael A. Covington" <> wrote
    in message

  4. #4
    Michael A. Covington's Avatar
    Michael A. Covington Guest

    Default UO abbe orthos?

    "shawn o'deal" <> wrote in message

    OK, both are about f/8. Typical eyepieces would be:

    Lowest usable power (7mm exit pupil): 55mm (requires a 2-inch tube)

    Low power (for deep-sky objects, 4mm exit pupil): 32mm

    Medium power (for higher contrast on deep-sky objects, 2mm exit pupil):

    High power (lunar and planetary, 1mm exit pupil): 8mm

    Maximum power (0.5mm exit pupil): 4mm

    So your highest-power eyepiece should be something in the 4 to 8 mm range; I
    suggest 8mm or so. Note that with an ortho, this will be an eyepiece that
    requires you to hold your eye very close to the eyepiece. You may find a
    Vixen Lanthanum eyepiece more comfortable; it gives you 20 mm of eye relief.

    Eyepieces don't work magic. When you're doing high-power planet viewing,
    the sharpness is not likely to be limited by the quality of the eyepiece.
    Use any good eyepiece that you find comfortable and affordable.

    Clear skies,

    Michael Covington --
    Author, Astrophotography for the Amateur
    and (new) How to Use a Computerized Telescope

  5. #5
    Jackie's Avatar
    Jackie Guest

    Default UO abbe orthos?

    "shawn o'deal" <> wrote in message

    UO orthos are my favorite, most-used EPs. I have had Naglers and Radians,
    but for the kind of viewing I do, you can't beat UO orthos. I have a
    Takahashi FS-102 and an Synta-made 90 mm f/11. If you don't mind short eye
    relief and narrower FOV's, I feel that orthos represent the best value in
    eyepieces around.


  6. #6
    kowen's Avatar
    kowen Guest

    Default UO abbe orthos?


    I agree with Jackie & Michael: about the UO's being sharp and
    contrasty, they also show up good detail in the lower contrast views
    like shadow detail on the moon, craters, etc. I've never looked
    through Naglers, Pentax or other hi-end eps except I have the .965 4mm
    Hi-Ortho Tak (excellent), but the seeing conditions are a big factor
    in viewing the planets at high power.

    I've had excellent-the best I've seen-views of Jupiter & Saturn with
    just my Shorty Barlow plus & my 10mm Sirius plossl-the views blew me
    away, showing much detail but the seeing conditions were probably
    close to perfect. I bought the UO 7mm classic ortho, and I do barlow
    that with my S. Plus 2x, giving me 258x on my 4.5xt (f7.9), and 290x
    with my C102hd (f/10) with no image break down ~unless~ the seeing is

    So, the most expensive ep may not necessarily be the best because
    seeing conditions have much to do with the views. I'd like to try the
    5mm UO classic or the (9mm barlowed) for Saturn & Jupiter; I think the
    5mm by itself would give more contrast and appear sharper. From
    everything I've read from owners & users, these are some of the
    sharpest, contrastier eps for the money.

    Hope this helps...


  7. #7
    Engineer Scott's Avatar
    Engineer Scott Guest

    Default UO abbe orthos?

    On Wed, 31 Dec 2003 03:12:00 GMT, "shawn o'deal" <>

    I love Ortho's. I've got an Orion 80ED and one of my favorite
    eyepieces I use with it is a Vixen 4mm Ortho. This give 150X with that
    scope. I also have a Takahashi 2.8mm high eye relief Ortho and It does
    a pretty good job also but most of the time the 4mm is the best. I
    personally don't care much for Barlows but that's just my personal
    preference. If I'm going to go to the trouble and effort to use an
    Ortho I'm trying to get the highest fidelity image possible and to me
    that means as little glass as possible. But a 7mm with a 2X Barlow
    would be a very good mach for the 80ED at 171X and a 6mm and 2X Barlow
    at 200X would be about the equivalent of the 2.8mm Tak Ortho.

    It's true the Ortho's have pretty short eye relief but it's better
    than a Plössl of the same focal length.

    I also like the longer Orthos. I have an excellent 12.5mm Vixen and
    also an 18mm Vixen. I usually start with these and then pump up the
    power. I have Pentax Orthos in 9, 7, 6 and 5mm so I can adjust for the
    seeing conditions. I think with these higher power eyepieces it makes
    sense to have a lot of magnifications near each other so you can pick
    the one that's just right. But most of the time the 80ED easily
    supports the 4mm.


  8. #8
    Alan W. Craft's Avatar
    Alan W. Craft Guest

    Default UO abbe orthos?

    On Wed, 31 Dec 2003 03:12:00 GMT, "shawn o'deal" <> ...reflected:

    It's very, very good, and I've only used mine once thus far.

    The University Optics orthoscopics are perhaps the greatest bargain
    in astronomical hardware...ever.

    My 4mm is superb!

    I'd get the UO 12mm Konig II 'stead of the 12.5mm orthoscopic.
    Of course, 'tis a bit pricier, but what a sharp field of view for the price!




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