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Thread: Barlows - useful for eyeglass wearers?

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    Default Barlows - useful for eyeglass wearers?



    Esteemed friends:

    Can you give me your opinion on whether Barlows are indeed useful in improving eye relief for a wearer of glasses and, in my case, one with a significant astigmatism?

    And since your hand is already on the keyboard, would you recommend a good one?

    Appreciated
    John

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    Default Re: Barlows - useful for eyeglass wearers?

    - Usually eyerelief is not improved, but not decreased too.
    - Astigmatism in the eyepiece is reduced. Off axis sharpness of the eyepiece is increased.
    - The smaller exitpupil as a result of using a barlow is a cause for observing less astigmatism with the same eyepiece too. The smaller the exitpupil, the less astigmatism an astigmatic eye sees.
    - Barlows tend to flatten the focal plane.

    The best is to keep your glasses on.

    A good and affordable one: Televue and Baader VIP modular. Expensive: Baader Zeiss.
    Last edited by John Baars; 01-03-2019 at 10:18 PM.
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    Default Re: Barlows - useful for eyeglass wearers?

    Sorry, I made a mistake. Couldn't correct it for I was timed out.
    The last one should be: Zeiss Abbe. Sold by Baader.
    Link to all three: https://www.teleskop-express.de/shop...er-Lenses.html
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    Default Re: Barlows - useful for eyeglass wearers?

    Barlows do affect eye relief, but this is small and negligible. However, many EPs like Orthos and Polssls have scalable design and eye relief (ER) decreases with focal length. In this case barlows are beneficial for glasses wearers. For example 10mm Plossl has very short ER, but combination of 20mm Plossl and 2x barlow results in effective 10mm focal length and very comfortable ER.

    I have a complex and strong prescription and prefer to observe with glasses on. Using barlow is a good option for me. Another route is to use EPs with long eye relief (15-20mm).

    For a good quality barlow I second John on Televue 2x and 3x barlows.

    https://www.highpointscientific.com/...-1-25-blw-2125

    More budget but still good choice is Baader Q-barlow.

    https://www.highpointscientific.com/...ulticoated-bqb
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