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  1. #1
    Bill Greer's Avatar
    Bill Greer Guest

    Default Orion Expanse E.P. Review



    Review of Orion Expanse 20mm, 15mm, 9mm, and 6mm eyepieces:

    Eyepieces arrived well packaged, looking new. The 20mm and 15mm had
    clear, rubber, stretch-to-fit caps over both ends. The 9mm and 6mm
    had more traditional, semi-flexible plastic caps -- black caps over
    the eye ends and off-white caps over the barrel ends. I liked the
    more traditional caps better. Time will tell whether my cold weather
    concerns with the stretch-to-fit caps will be justified or not . . .

    Day testing and impressions using ST-80 (72.5mm aperture, 400mm focal
    length):

    Wide apparent field. Not sharp near field edge. Comfortable eye
    relief without eyeglasses. Eye relief a bit too short for comfortable
    use with glasses on. Eye position was critical with the 9mm. Part of
    the field would black out if the eye placement wasn't just right. The
    other eyepieces in the set were more forgiving of eye placement. The
    central area of the fields seemed sharp and well corrected.

    Since the ST-80 is my "fastest" scope (meaning it's the scope that
    provides the largest, easiest to measure exit pupils), I used it to
    focus on a distant hill top in order to measure exit pupils. A
    homemade dynamometer marked at 1/10 mm intervals was used. A dark
    green filter was added to make it easier to measure the small disks of
    light.

    I took into account that my ST-80 has an effective aperture of about
    72.5mm and a focal length of 400mm when I calculated magnification and
    then 'reverse-calculated' the focal lengths of the eyepieces. The
    calculated focal lengths were within 1mm of the stamped focal lengths
    on all eyepieces except the 9mm. The 9mm eyepiece had a calculated
    focal length of about 10.4mm, but errors in my measurements may have
    contributed to that result. There were plenty of opportunities for
    errors to creep into my measurements!

    Night testing and impressions using a 5 inch f/6 apochromat:

    Actually, I was out last night under a mostly cloudy sky making
    transit timings in order to calculate true fields of view of all the
    eyepieces with and without each of my two barlows. It wasn't until
    this morning that I decided to write this review. The clouds were
    such that extended observations of any single object were impossible
    to make. Nevertheless, some things were noticed:

    The field edges were judged to be adequate for providing a 'context'
    or background for whatever was being studied in the field center; but
    they were insufficiently sharp for any kind of critical work. The
    field centers were sharp and well corrected.

    Eye relief impressions were identical -- in every way -- to the
    daytime eye relief (and eye placement) impressions.

    The star I used for transit measurements was Theta Aquilae (magnitude
    3.2). A ghost reflection of the star was obvious in the 6mm eyepiece.

    I was able to observe Mars as clouds repeatedly passed over and
    uncovered it. The situation was too chaotic for me to consider making
    any sketches. Nevertheless I was able to gain at least a vague
    comparison between a 6mm U.O. Orthoscopic and the 6mm Expanse. A TV
    2x barlow was used with both eyepieces. The Expanse was *far* more
    comfortable to use -- much better eye relief than the Orthoscopic.
    The Expanse insisted on creating a prominent ghost image of the red
    planet -- easy enough to ignore, but it did make for a cosmetic flaw
    in the view. The Orthoscopic produced a 'cleaner' image. Both
    eyepieces showed the most prominent Martian features. Unsteady seeing
    and frequent dodging of clouds prevented me from making a more
    critical comparison. The telescope was used straight through --
    without a star diagonal.

    Indoor calculations and observations:

    From my magnification and true field of view determinations I was able
    to calculate the apparent fields of the Expanse eyepieces. The
    calculated apparent fields ranged from 61 to 66 degrees with an
    average of 64 degrees. Considering all the opportunity for errors to
    creep into my calculations, I believe it's fair to say that the
    Expanse eyepieces meet the advertised, wide 66 degree apparent fields
    of view.

    A white light was used to check the optical coatings of the eyepieces
    this morning. In general, each Expanse eyepiece had one green
    reflection, a small number of blue reflections, and mostly white
    reflections. In other words, the optical coatings weren't very good.
    As discovered last night, the coatings were insufficient to prevent
    ghost images of small, bright objects.

    Final opinion (at this point in time):

    For the price ($182.95 delivered) this set of four eyepieces is a good
    deal. (I expected less than perfect edge-of-field quality. One
    generally has to pay for perfection!)

    I still need to make some critical comparisons on deep sky, the moon,
    and planets before deciding if any of these eyepieces end up in my
    regular observing arsenal.

    The wide apparent fields, the comfortable eye relief, and the
    relatively low price make these eyepieces attractive for use with
    visitors and children. (I just couldn't bear thinking about showing
    Mars to my wife's parents using a 6mm Orthoscopic eyepiece!)

    Bill Greer

  2. #2
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default Orion Expanse E.P. Review

    >The wide apparent fields, the comfortable eye relief, and the

    Bill:

    Nice review. I have a set from Adorama and nearly all my experiences agree
    nicely with yours. I also have some UO orthos but since these eyepieces
    arrived, the orthos (and my Plossls as well) just sit.

    I haven't noticed the positioning problem you did with the 9mm, wonder if
    something is not quite right there. The 6 and the 9 mm both have a secondary
    lens, a Smyth or Barlow lens or some such thing. Both these came loose after a
    short while. I removed the 1.25inch section and tighted them up from the top,
    since then, no problems.

    I have been using mine for seveal months now, I think these eyepieces are a
    great bargin and a definite upgrade from standard and even premium Plossls.

    jon




  3. #3
    Pete Rasmussen's Avatar
    Pete Rasmussen Guest

    Default Orion Expanse E.P. Review

    On Mon, 21 Jul 2003 14:08:15 -0600, Bill Greer
    <sketcher@strangeweb.net> wrote:


    <snip very nicely done review>

    Hi Bill,

    My Orion 9mm Expanse is the only one I have so far and I agree it is
    just a little bit tricky to use. On coatings, if you screw the upper
    housing off and opaque the lenses you will see with light source all 4
    A-G surfaces are mulicoated. At least mine is. The negative achromat
    in the barrel is fully coated presumably with mag fluoride. That
    aspect is very light (nearly white) magenta colored and would
    potentially explain your notation about "white" surfaces. IOW,
    coatings on mine are excellent.

    Also, I have done preliminary testing and this wide-angle model
    appears extremely sharp with excellent contrast for moon and planets.
    That is exceptional for the type and highly useful with undriven Dobs
    for same viewing.

    One problem I see is the internal mechanics need user modifications to
    improve the contrast to full potential, and eliminate bright object
    glare and ghosting. The inside of the upper housing can extremely
    easily be flocked by auser simply unscrewing and removing the top and
    bottom lens assemblies to access it. However, the nasty, shiny lens
    spacer between the upper lens assembly is more difficult to get at,
    but is not impossible to access to deaden. Upon completion the
    eyepiece would be fantastic.

    Clear skies,

    Pete

  4. #4
    Pete Rasmussen's Avatar
    Pete Rasmussen Guest

    Default Orion Expanse E.P. Review


    I'd like to add as update that there seems no problem at all using the
    9mm Expanse when an eye pupil is expanded somewhat. Deep sky viewing
    with a pair is fantastic and very comfortable. Only when viewing a
    brightly illuminated moon does this eyepiece design seem to get antsy.
    Additionally, I was viewing Mars last night at 300x through a large
    Dob with my pair of these attached and the views were truly excellent
    with plenty of drift space to tag the planet. There were a couple of
    minor floating ghosts outbound of field center but they were not
    distractive to me.

    Clear skies,

    Pete


  5. #5
    Rod Mollise's Avatar
    Rod Mollise Guest

    Default Orion Expanse E.P. Review

    > I was viewing Mars last night at 300x through a large

    Hi:

    I've got the 6mm, and it acquitted itself well on Mars last weekend at 300x.
    Even close to 500x, it was doing fine, with the seeing being the main culprit
    in any yuckiness. Very nice, reasonably priced eyepieces IMHO. I'll probably
    buy a couple more.

    Peace,
    Rod Mollise
    Author of _Choosing and Using a Schmidt Cassegrain Telescope_
    Like SCTs and MCTs?
    Check-out sct-user, the mailing list for CAT fanciers!
    Goto <http://members.aol.com/RMOLLISE/index.html>

  6. #6
    Rod Mollise's Avatar
    Rod Mollise Guest

    Default Orion Expanse E.P. Review

    >Very nice, reasonably priced eyepieces IMHO. I'll probably

    Oh...and let me add...Scopestuff and Adorama sell the very same eyepieces for
    less $$$.

    Peace,
    Rod Mollise
    Author of _Choosing and Using a Schmidt Cassegrain Telescope_
    Like SCTs and MCTs?
    Check-out sct-user, the mailing list for CAT fanciers!
    Goto <http://members.aol.com/RMOLLISE/index.html>

  7. #7
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default Orion Expanse E.P. Review

    >I've got the 6mm, and it acquitted itself well on Mars last weekend at 300x.
    Ron: Glad to hear you like, I like mine, not having any Naglers or Panoptics,
    these are about all I use.

    I have had good success with mine 6 at high powers but there are some internal
    reflections when bright objects are not centered. Have you noticed this with
    yours, maybe they had fixed this??

    I have the 6, 9, and 15mm, the 9 is the best of the lot IMHO.

    jon

    jon

  8. #8
    Rod Mollise's Avatar
    Rod Mollise Guest

    Default Orion Expanse E.P. Review

    >

    Hi:

    Did not notice any.

    Peace,
    Rod Mollise
    Author of _Choosing and Using a Schmidt Cassegrain Telescope_
    Like SCTs and MCTs?
    Check-out sct-user, the mailing list for CAT fanciers!
    Goto <http://members.aol.com/RMOLLISE/index.html>

  9. #9
    Pete Rasmussen's Avatar
    Pete Rasmussen Guest

    Default Orion Expanse E.P. Review

    On 23 Jul 2003 23:19:53 GMT, rmollise@aol.com (Rod Mollise) wrote:


    Yup, they are definitely very good multi-use wide-angles (MUWA's ?).
    Have very good sharpness and the color error too often found with this
    type is pretty darn low! Funny, that "ghost" situation seems not to
    be visable at all times. Like a _real_ one? <g>

    My viewing this morning was to 417x (usually at 370x) with Mars and,
    near dawn, the moon. Scope a loaned for upgrade large aperture Dob
    Newtonian. I compared the pair of 9mm Expanse to a pair of University
    9mm HD orthos in my Zeiss binoviewer. As expected, the orthos
    resolved better, were more contrasty, a little lower in color error,
    and a hair brighter. Alas, both 9mm pairs remain as handy keepers as
    the Expanse is dynamite for wide-eyed viewing of the moon. Especially
    after baffling them I bet. Can't wait to try the 15mm pair of Antares
    (exact same?). They should be here tomorrow

    Pete

  10. #10
    Pete Rasmussen's Avatar
    Pete Rasmussen Guest

    Default Orion Expanse E.P. Review

    On 23 Jul 2003 23:53:54 GMT, jonisaacs@aol.com (Jon Isaacs) wrote:


    Jon,

    Why not unscrew and remove the top and bottom assemblies to access and
    flock the lower half of the middle housing I.D.? You would find it
    incredibly easy and quick to accomplish. Will need to leave portion
    unflocked where the top section goes back in. That's it, and should
    take care of most of the problem.

    Pete

 

 
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