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Thread: Barlow+Ortho

  1. #31
    John Baars's Avatar
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    Default Re: Barlow+Ortho



    A good achromatic barlow has normally two lenses, which are kitted together. Only two glas-air surfaces. That's good news for transmission and lightscattering.
    More good news: The average CA of an ED achromat is 1/4000 F.
    Since the F of a ED barlow is many times shorter than your telescope's F, the total amount of CA of your achromatic barlow in microns is even less than the CA of a normal APO. In other words: you won't notice it.

    Apochromatic ( and triplet)barlows are build to be short. If you don't need a short barlow ( to reach focus for instance), normal achromatic barlows of good quality are all you need.
    Telescopes in Schiedam : SW Evostar 120ED F/7.5, Vixen 102ED F/9, OMC140 maksutov F/14.3, SW 102MAK F/13 on Vixen GPDX.
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  3. #32
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    Default Re: Barlow+Ortho

    Quote Originally Posted by not_Fritz_Argelander View Post
    I don't know the TS barlow you're considering.
    I know I'm being boring, I'm sorry for that. But it's only to say that the TS Optics 2x and 1.5x Achromatic Barlow is nothing more, nothing less than the GSO 1.25 "shorty" Achromatic Barlow. Telescope Service guys only change the name "GSO" to "TS", exactly as they did with the Newtonian I bought them. "https://agenaastro.com/gso-1-25-2x-achromatic-barlow-lens.html?SID=m67nsjsclsfop6picrctdf4757"
    TS (GSO) 150/900 Newtonian Telescope; SkyWatcher 130/900 Newtonian Telescope; KONEX 10x50 Binoculars
    Omegon Serie LE 5mm 1.25" EyePiece; Skywatcher Super MA 10mm 1.25" Eyepiece; Skywatcher Super MA 25mm 1,25" Eyepiece
    Skywatcher 1.25" 2X Barlow lens

  4. #33
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    Default Re: Barlow+Ortho

    Quote Originally Posted by John Baars View Post
    A good achromatic barlow has normally two lenses, which are kitted together. Only two glas-air surfaces. That's good news for transmission and lightscattering.
    More good news: The average CA of an ED achromat is 1/4000 F.
    Since the F of a ED barlow is many times shorter than your telescope's F, the total amount of CA of your achromatic barlow in microns is even less than the CA of a normal APO. In other words: you won't notice it.

    Apochromatic ( and triplet)barlows are build to be short. If you don't need a short barlow ( to reach focus for instance), normal achromatic barlows of good quality are all you need.
    Great news! Thanks.
    TS (GSO) 150/900 Newtonian Telescope; SkyWatcher 130/900 Newtonian Telescope; KONEX 10x50 Binoculars
    Omegon Serie LE 5mm 1.25" EyePiece; Skywatcher Super MA 10mm 1.25" Eyepiece; Skywatcher Super MA 25mm 1,25" Eyepiece
    Skywatcher 1.25" 2X Barlow lens

  5. #34
    not_Fritz_Argelander's Avatar
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    Default Re: Barlow+Ortho

    Quote Originally Posted by JPAG View Post
    I know I'm being boring, I'm sorry for that. But it's only to say that the TS Optics 2x and 1.5x Achromatic Barlow is nothing more, nothing less than the GSO 1.25 "shorty" Achromatic Barlow. Telescope Service guys only change the name "GSO" to "TS", exactly as they did with the Newtonian I bought them. "https://agenaastro.com/gso-1-25-2x-achromatic-barlow-lens.html?SID=m67nsjsclsfop6picrctdf4757"
    Likely it's just fine. I've used this one and as noted in another post, color was not a problem.
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  7. #35
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    Default Re: Barlow+Ortho

    Hello again. This forum was inaccessible for several days, with great pity of mine.

    About the ortho eyepiece and the barlow, I thought a lot and decided to buy these two items:

    <https://www.teleskop-express.de/shop/product_info.php/info/p8857_Kokusai-Kohki-Fujiyama-HD-OR-9mm---a-classical-Abbe-ortho.html>
    That's not a new.

    and

    <https://www.teleskop-express.de/shop/product_info.php/language/en/info/p1892_TS-Optics-TSShorty-2x-Apo-Barlow--1-25-inch--3-element---for-observing-and-astroph.html>
    That's a new!

    About this barlow which is the same as that (only changes the brand name): https://www.firstlightoptics.com/bst...rlow-lens.html
    What's your opinion? Has anyone ever used it?
    Last edited by JPAG; 12-09-2017 at 08:36 PM. Reason: Error in links.
    TS (GSO) 150/900 Newtonian Telescope; SkyWatcher 130/900 Newtonian Telescope; KONEX 10x50 Binoculars
    Omegon Serie LE 5mm 1.25" EyePiece; Skywatcher Super MA 10mm 1.25" Eyepiece; Skywatcher Super MA 25mm 1,25" Eyepiece
    Skywatcher 1.25" 2X Barlow lens

 

 
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