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  1. #1
    Gaz's Avatar
    Gaz Guest

    Default 127mm Mak-Cas or Orion 80ED?




    hi all,

    I'm looking for a small scope to use on the moon and planets, assuming
    cool down isn't a problem, has the refractor got anything to offer over
    the Mak-Cass?

    cheers
    gaz


  2. #2
    Szaki's Avatar
    Szaki Guest

    Default 127mm Mak-Cas or Orion 80ED?


    "Gaz" <reds4ever@gmail.com> wrote in message
    news:1107016559.777882.46540@f14g2000cwb.googlegro ups.com...

    No central obstruction(nice for double stars), much wider field view, able
    to go lower power, no collimation hassle, no cool down time, smooth images,
    more contrast etc...
    Julius





  3. #3
    Tim Killian's Avatar
    Tim Killian Guest

    Default 127mm Mak-Cas or Orion 80ED?

    Assuming equal optical quality, the 127 mm Mak is equivalent to an 80 mm
    refractor for lunar and planetary observing. The refractor would be
    better suited for photography and low power/daytime use.


    Gaz wrote:


  4. #4
    Gaz's Avatar
    Gaz Guest

    Default 127mm Mak-Cas or Orion 80ED?


    Tim,

    I didn't know that, I'd assumed I'd be losing a bit of resolving power
    on the planets if I choose the ED , it was the main reason i was
    leaning towards the Mak. Otherwise, as Szaki points out, i could have
    a larger FOV, skip collimation etc.

    Gaz


  5. #5
    Tim Killian's Avatar
    Tim Killian Guest

    Default 127mm Mak-Cas or Orion 80ED?

    In terms of resolving power, the equivalent refractor aperture is
    roughly equal to the aperture of the Mak minus the diameter of its
    central obstruction. Collimation and cool down are not big issues with
    small aperture Maks.

    One advantage for the refractor I forgot to mention is less scattered
    light because there are no extra reflections involved, This will give
    slightly more contrast on planets.


    Gaz wrote:



  6. #6
    David Nakamoto's Avatar
    David Nakamoto Guest

    Default 127mm Mak-Cas or Orion 80ED?

    While I agree with other posters about the optical properties of the refractor,
    there are two things that you should also keep in mind. First, the Mak you
    mentioned is capable of over 2.5x the magnification of the refractor you
    mentioned due to its focal length, not a trivial consideration when it comes to
    the Moon and planets, where magnification is as important as clarity of view.
    Second, the Mak will have less color dispersion, giving cleaner images than the
    refractor - no blue fringes on planet or Moon images.

    And I know of three of those Orion Maks, one I own, and they've all performed
    better than an equivalent sized Mak and according to one guy I trust, better
    than an 8-inch SCT. While a well-made Mak will not outperform a well-made
    refractor, the refractor you mentioned is a two element one with a relatively
    short focal ratio of f/7.5, and making a good one takes more effort than the
    Mak, so you're chances of getting a good Mak is better than the refractor, in my
    opinion, given what I've experienced.

    --
    Sincerely,
    --- Dave
    ----------------------------------------------------------------------
    It don't mean a thing
    unless it has that certain "je ne sais quoi"
    Duke Ellington
    ----------------------------------------------------------------------

    "Gaz" <reds4ever@gmail.com> wrote in message
    news:1107016559.777882.46540@f14g2000cwb.googlegro ups.com...



  7. #7
    Szaki's Avatar
    Szaki Guest

    Default 127mm Mak-Cas or Orion 80ED?


    "David Nakamoto" <res07oeg@verizon.net> wrote in message
    news:wqQKd.403$zb.85@trnddc07...

    That's a bull! Orion 80ED should do 250x or more any day, so 2.5x the Mak127
    magnificatain, as you suggesting, would put it over 600x. Never
    happened!Hahahaha!
    I owned 6" Intes-Mak-Cass, much finer and more expensive OTA than the Orion
    127 Mak, but it had to have excelent seeing to perform. My 3" f/15 Edscorp
    refractor regularly out perfomed the 6" Mak when the seeing was not there.
    Mak has a larger central obstruction (<37%) than an SCT has, so one has to
    deal with large, multable diffrection rings around stars or the moons of
    Jupiter.
    Person who used to refractor images, would puke.
    Julius





  8. #8
    David Nakamoto's Avatar
    David Nakamoto Guest

    Default 127mm Mak-Cas or Orion 80ED?

    Szaki, you're thoughtless in your answers, as simple math will show.

    We're talking about an f/7.5 system in the 80ED, which you would have known if
    you took the time to visit the Orion website, and thought anything about giving
    correct answers instead of "showing off", and doing research before writing
    anything down. This means the focal length is 600mm. Since "focal length of
    telescope" / "magnification" = "focal length eyepiece", 600 / 250 = 2.4 mm.
    Even if such an eyepiece exists, it also means you're pushing 80x per inch
    aperture in a two element 80 mm telescope, only possible with the best optics
    (which the Orion is not), long telescope focal ratios, and under absolutely
    steady nights.

    And your comparison is not correct either. You're comparing a 3-inch f/15
    refractor to a 3-inch f/7.5 refractor (the Orion ED). No matter what you do,
    you cannot achieve as much magnification through the same eyepieces from the
    latter as through the former. As anyone who knows optics knows, figuring and
    testing long focal ratio systems is easier than short focal ratio systems
    (steepness of curves as well as tighter requirements on the figure of the curves
    for the short focal ratio systems are two reasons). I have no doubt that a
    3-inch f/15 refractor, if properly made would outperform a similarly sized Mak
    (127 mm aperture and f/12 focal ratio) but we're not comparing such a Mak to an
    f/15 instrument, but a much shorter focal ratio instrument. Color dispersion is
    greater in such systems and affects performance, while the Mak is more immune to
    such effects.
    --
    Sincerely,
    --- Dave
    ----------------------------------------------------------------------
    It don't mean a thing
    unless it has that certain "je ne sais quoi"
    Duke Ellington
    ----------------------------------------------------------------------

    "Szaki" <szaki10@comcast.net> wrote in message
    news:Cf6dnVEC9em8mmHcRVn-3Q@comcast.com...



  9. #9
    Szaki's Avatar
    Szaki Guest

    Default 127mm Mak-Cas or Orion 80ED?

    I'm a user not a builder of telescopes. Good quality APO refractor, one can
    push over 100x per inch on a good seeing night, compound telescopes like the
    Mak, lucky if you can do 50X.
    I'm getting tired of arguing with Newt,Mak, SCT guys about this, cause I
    know they put down refractors for the price/aperture.. What I'm telling you
    is from experience, not from theory.
    I owned all those scopes, but I don't give up my refractor. After owning
    many telescopes, I settled to C102F APO refractor (most used), 4" Mak(
    MTO-11CA 10/1000 Telephoto Lens) for portability and a Ultima C-11 OTA for
    DSO's. They all fit on my EQ mount or the GiroII for alt/az movement.
    All these telescopes are very portable and easy to store, I know the pros
    and cons of these scopes also.
    My 4" Mak don't even come close to my TV Pronto I use to own. I heard good
    things about the Orion80ED.
    One has to use barlows for short focus length refractors, to get higher
    magnification, that's all. I hate to use a Mak for terrestrially, long focus
    length, narrow field. Yak!!!!
    JS




    "David Nakamoto" <res07oeg@verizon.net> wrote in message
    news:i6UKd.1078$UB6.973@trnddc01...



  10. #10
    David Nakamoto's Avatar
    David Nakamoto Guest

    Default 127mm Mak-Cas or Orion 80ED?

    "Szaki" <szaki10@comcast.net> wrote in message
    newsr6dneujJY1RvGHcRVn-vQ@comcast.com...

    Same here. Obviously you're not reading my message carefully enough. I pointed
    out legitimate and KNOWN deficiencies in relatively short focal ratio
    inexpensive two-element refractors, while acknowledging the benefits that others
    have pointed out.

    And what you call theory is the collective wisdom of many decades of visual
    amateur astronomer experience from a lot of people on this newsgroup. You
    obviously have a strong and I must say skewed bias toward refractors, without
    taking into account the differences in performance brought about by such things
    as focal ratio, two vs. three-element design, et al.

    And I own a short focal ratio refractor, so I know something from personal
    experience, if you're going to tout that out as your badge of authority. And
    one thing I would not do, which you do, is to think that a refractor is a
    refractor is a refractor. Focal ratio and objective design DOES MATTER, but I
    doubt you understand this, given your responses to my messages.

    Whatever experience you think you have, it's clear to me you need a lot more
    before you can make cogent and fact-backed statements. That, and read the
    messages your responding to more carefully.




    So have I, but the fact remains that those reports I've gotten from observers
    who I know to have lots of experience evaluating telescopes of various designs
    and makes have said it was good for a two-element short focal length refractor,
    meaning it will perform within the expectations of such a telescope, and NOT
    like a longer focal ratio one, or a three-element one, or an expensive one, et
    al.



    But the Mak will deliver 2.4 times the magnification for the same eyepiece, so
    it is also capable of delivering higher magnification, important for planetary
    viewing. And in any case, I don't think that, given what I've heard and seen of
    the Orion 80ED at star parties, that you can push it much past 30x per inch of
    aperture, so your objection that this is the "limit" on the Mak (something I
    also disagree on, from collective experience) is moot.

    And the original poster asked specifically for planets and the Moon. Why drag
    terrestrial viewing when it was not specified? In this case, the Mak is an
    instrument he should consider, given that for a given eyepiece it will deliver
    more magnification, less color dispersion, and potentially sharper views, if the
    contrast isn't too bad.

    --
    Sincerely,
    --- Dave
    ----------------------------------------------------------------------
    It don't mean a thing
    unless it has that certain "je ne sais quoi"
    Duke Ellington
    ----------------------------------------------------------------------





 

 
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