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  1. #1
    HarryBnBad's Avatar
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    Default Barlow or Powermate



    I think I'm sold on getting a tv barlow. Unless someone can tell me why I'd like the powermate better. Seams like thier web site says something about taking barlows to the next level....

  2. #2
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    Default

    The advantage of the Powermate is it keeps eye relief exactly where the manufacturer put it.
    Barlows increase the eye relief slightly although this isn't usually a problem, but it can be on eye pieces with already long eye relief.
    Regards Steve
    Steve

  3. #3
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    Default

    A PowerMate is a Telecentric Barlow.

    A Barlow adds magnification to a telescope by divering the light comming towards focus.

    Eyepieces are designed to deal with parallel converging light cones (not diverging ones). When an EP deals with a diverging light comming to focus, the exit pupil is moved farther from the eye lens.

    Some Eyepieces display an optical malady called vignetting when used with a Barlow. PowerMates were designed to give the Barlow magnification effect without causing the vignetting effect.

    There was an intermediate form between Barlow and PowerMate. This form used a TV 2X 2" Barlow with an "Interface" lens. Taken together these are in essence a PowerMate.
    Attached Images Attached Images

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    akjudge (12-25-2011),G4Jon (06-08-2013),HarryBnBad (12-23-2011),Schlayer (01-05-2012)

  5. #4
    HarryBnBad's Avatar
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    Default

    Ok, now that I have the meade zoom, I'm ordering the 2.5 powermate....

 

 

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