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  1. #1
    silvereagle100's Avatar
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    Smile Sky Watcher LET Long Eye-Relief Eyepieces



    I have a question about the eyepieces that came with my Skywatcher refractor. As some of you may know, Skywatcher sends no literature (beyond a warranty) with their product. Anyway I noticed the the eye cups appear to be adjustable. This in what I found in a write up on one website: "Sky Watcher LET Eyepieces also feature a continuously adjustable twist top eyecup design which accommodates eyeglasses while blocking stray light from interfering with your view."

    Does this mean it will make a correction for my eyesight if I am viewing without my eyeglasses? Or what?

    I have already written to Celestron support and received a link to a good but nevertheless generic article on eyepieces. They also told me not to take them apart (well...duh) I may be ignorant but I am not that stupid.

    Thanks, Silvereagle

  2. #2
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    Eye relief is built into the design of the EP. Eyecups are to help eliminate ambient light. Sometimes you can adjust your eyecup so that you can lightly rest your brow, or your eyeglasses, against it to help steady your gaze.
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  3. #3
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    Quote Originally Posted by silvereagle100 View Post

    Does this mean it will make a correction for my eyesight if I am viewing without my eyeglasses? Or what?

    Thanks, Silvereagle
    The eyecup will not correct for your eyesight, but your focuser can correct for near and farsightedness. Simply turn the knob on the focuser until the object is in focus. That does not work for astigmatism though. So if you have that then you will have to observe with your glasses. At least at large exit pupils, at small exit pupils astigmatism becomes much less noticeable.
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    WWPierre's Avatar
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    .....At least at large exit pupils, at small exit pupils astigmatism becomes much less noticeable.
    Thanks, I have noticed I can see without my glasses sometimes better than others. Never connected it with anything.
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    wallcreeper's Avatar
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    A rough formula to determine at what exit pupil you can do without glasses is: 2/D, in which D stands for the diopter value of your eye. I have read that for others a 3/D or even 4/D works better. For me the 2/D seems about right. My Diopter value is 1, so the formula world say that at 2mm exit pupil I should be ok without my glasses. From experience this works for me. For example at a 3mm exitpupil I really need my glasses or else the stars will not look sharp.
    Something worth finding out, since you will not have to buy more expensive long eyerelief eyepieces at those exitpupils.
    Here is a link to a Televue article on the topic.
    http://www.televue.com/Pdf/Obs_Acc_D..._TechNotes.pdf
    Last edited by wallcreeper; 11-16-2010 at 02:21 AM. Reason: added link
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  6. #6
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    Thank you all for the help

    Silvereagle

 

 

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