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Thread: EP design

  1. #1
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    Default EP design



    What is it about the design of Orthos that make them the choice for planetary viewing but not for DSOs?
    Intercepting & temporarily inconveniencing light photons as they travel through the universe since 1989
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  2. #2
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    Default Re: EP design

    Hello Nimitz,

    the orthos are often the best choice even for the nebulae and galaxies, whenever the angular size of the nebulae or galaxies, when multiplied by the magnification, fits comfortably into the 40° AFOV of most orthos.
    The Baader BCO orthos have enjoyed some popularity, as they offer 52° AFOV, and the lost of sharpness towards the edge of the field of view is still acceptable.

    Best,

    JG
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  4. #3
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    Default Re: EP design

    There's another aspect of ortho eyepieces, the are an optical match with refractors, SCTs and Maks. The plossl design is just as proficient as orthscopics, but in Newts. The problem around plossls is they are available extremely cheaply and of great quality variations than orthos, so plossls don't carry the same street cred as orthos.

    However, the new eyepiece designs that use new and very exotic glass types coupled with new superior coatings, these EPs are overtaking orthos for image quality, with the added benefits of wider AFOV, much larger eye lens, and very generous eye relief. It is not right to keep saying that a 150 year old eyepiece design that uses old glass types is still superior to the new crop of EP designs. I too used to think that EPs with fewest number of elements was the ONLY way to go. I've now seen different, & a hell of a lot more comfortable.

    Some manufacturers, such as Vixen, have also produced some exquisite new eyepieces that literally poop all over orthos. But because it is Vixen, they are largely unknown outside of Japan. These particular EPs, like orthos, are designed for refractors, which is the main instrument type in the Japanese market.

    Alex.

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    Default Re: EP design

    An Orthoscopic eyepiece as JG stated are the best choice for any target that will comfortably fit in the smaller FOV of the design.
    Though wider fields are good to excellent eyepieces, 60°+ AFOV eyepieces are always a trade off between AMD (Angular Magnification Distortion) or RD (Reticular Distortion) and the designer must decide which will be suppressed while masking the other.
    The Orthoscpic design with its narrower FOV does not suffer from these aberrations. They also do not suffer from EOFB (Edge Of Field Brightening) which can and does affect some wide fields.
    An Orthoscopic can be between 4 - 7 elements depending on the design. The Abbe Orthoscopic eyepiece is a 4 element in 2 groups design (1 - 3) which some people assume defines the "Orthoscopic" criteria.
    Though Plossl designs are also excellent, depending on the design of it asymmetrical or symmetrical and the spacing between the doublets they can show a bit of softening of the on axis FOV at times.
    If you read observing reports from various deep sky observers you will find that they rated the Orthoscopic as being able to dig deeper than even a TeleVue Ethos or Delos eyepiece.

    A high quality Orthoscopic requires top quality glass, coatings and requires more precision to manufacture than a wide field eyepiece.
    Refractors: Antares 105 f/15, Celestron 150 f/8, Stellarvue NHNG 80 f/6.9, TAL 100RS f/10, TS 102 f/11, UR 70 f/10, Vixen SD115s f/7.7
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  6. #5
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    Default Re: EP design

    Hello all,

    I basically agree with Alex on the new technologies for the EPs,

    Quote Originally Posted by mental4astro View Post
    ...
    However, the new eyepiece designs that use new and very exotic glass types coupled with new superior coatings, these EPs are overtaking orthos for image quality, with the added benefits of wider AFOV, much larger eye lens, and very generous eye relief. It is not right to keep saying that a 150 year old eyepiece design that uses old glass types is still superior to the new crop of EP designs. I too used to think that EPs with fewest number of elements was the ONLY way to go. I've now seen different, & a hell of a lot more comfortable.
    ...
    Alex.
    The Plössls, Abbe orthos and Steinheil monocentrics, are the legacy of the 19th and 20th century.
    And when well manufactured by Zeiss or TMB, they are super, not loosing their monetary value,
    true assets in our epoch of zero interst monetary policy.

    Well, there are competing designs, like the Leitz Periplan, optimized originally for the UV/violet and fluorescence highest resolution microscopy, which find their use in astronomy as well. The optimization and the high level of corrections for the wavelengths shorter than 500nm is top important for the nebulae and galaxies.

    Right now, I have recieved a brand new latest Leica eyepiece, developed for their newest APO microscopes.
    The first green laser beam trace test reveals again a new design concept, with some ED lenses inside and multicoatings, all Leica proprietary, not seen elsewhere.
    Will write a review, weather permitted, and I also need some time for writing.

    In Germany and also in the U.S., we can see a trend pointing away from the more or less "consumer" astronomy eyepieces, looking for something different. That's not just a hype, IMHO.

    Best,

    JG
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  7. #6
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    Default Re: EP design

    Quote Originally Posted by Nimitz View Post
    What is it about the design of Orthos that make them the choice for planetary viewing but not for DSOs?
    Oh, orthoscopics are for DSOs all right. I can detect fainter objects and get more internal details from orthos than other designs. Orthos are not any longer limited to crown and flint glass either. The smaller number of elements and surfaces makes control of contrast reducing scattered light an easier task. I find that they work well for me on f5 and slower Newtonians as well. At f4, I prefer Plossls.

    Language, though. Orthoscopic means no angular magnification distortion aberration. So the 3+1 lens grouping is an Abbe Orthoscopic but the 2+2 grouping due to Plossl is also orthoscopic. The identification of orthoscopic with the Abbe design is a case of common language use running away from the facts.

    For discriminating internal detail in DSOs the Abbe style Orthoscopics like the BCO and KK lines are best. For detecting the nebula at all the Plossl style of orthoscopic eyepiece from TV works best for me.
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  9. #7
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    Default Re: EP design

    Quote Originally Posted by Nimitz View Post
    What is it about the design of Orthos that make them the choice for planetary viewing but not for DSOs?
    Others already covered DSO part. I would just add that Orthos excel on planets because of the sharpness and excellent light scatter control. Light scatter is a function of the quality of EP finishes, number of glass elements, number of glass to air surfaces and quality of coating. While most of good quality EPs have good finishes and coating, Orthos still have an edge due to smaller number of glass elements and glass to air surfaces.

    Saying that there are other, more modern designs which do great job on planets to.
    Scopes: Celestron: 8" SCT F10, Omni 150R Achro F5, Onyx 80ED F6.3; ES: 127mm CF F7.5 APO; Meade: ST80 F5. Mounts: ES Twilight I, Bresser EXOS2, SW SkyTee2, AzGTi, UA MicroStar. Binos: Orion 15x70, 10x50, Nikon 8x40. EPs: Pentax: XWs; TeleVue: Delites, Plossls & barlows; ES: 82os & 68os; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV; Meade: UWAs & Plossls. Filters: Astronomik: UHC; Lumicon: OIII, H-beta, DeepSky; Baader: UHC-S, M&SG, CB; Orion: UltraBlock, SG. DSO tally: 1192 (H400-1: 400, H400-2: 302, H300-3: 87; M110: 110, S110: 73). Doubles: 772, Comets: 11, Asteroids: 59
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