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Thread: Calculating Magnification of Telescope from Eyepiece and Focal Length

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    Arrow Calculating Magnification of Telescope from Eyepiece and Focal Length



    Here I will describe how to calculate the magnification of of your telescope from the eyepiece and and telescope focal Length.


    To calculate:

    Magnification = Focal length of the telescope / Focal length of the eyepiece

    so for example:

    Magnification = 900 mm / 9 mm

    Magnification = 100X

    The telescope with an eyepiece of 9mm would magnify the object (eg moon) you are viewing 100X.

    Download an EXCEL file that will automatically calculate every possible eyepiece for your telescope and the resulting magnifications:

    http://www.astronomyforum.net/downlo...?do=file&id=18
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    Hi
    This is my first go at this forum
    I have a 8in Dob (skywatcher) wich I am told is good for 400x
    under good conditions.
    Do you think I should get a 3mm eye peice
    And where would I get one in Australia

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    hey 7715

    that would be 333x and you would have to be under extrem good conditions to see really good.

    on a good nite i up it too 300x on jupiter but like i said u need exteme conditions.

    but for a good eyeview a 5mm would be ok,, 1000/5 =200x
    i have a 12.5 in a barlow and i push it to 240x .
    but with good eps around 150x to 180x you get great views thats for sure..
    Celestron C9.25 moonlte CS, explore scientific AR102, Skywatcher mak102mm, Orion short 80mm, Celestron Cg5, Canon t3, Philips spc900nc, dbk21au618 ,ZWO ASI224MC

    flicker. https://www.flickr.com/photos/74059838@N00/

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    Quote Originally Posted by 7715gra View Post
    Hi
    This is my first go at this forum
    I have a 8in Dob (skywatcher) wich I am told is good for 400x
    under good conditions.
    Do you think I should get a 3mm eye peice
    And where would I get one in Australia
    Hi 7715 ...Welcome aboard the forums ... I have a 8in. sct with a focal length of 2000mm and use my 5.5 on the moon only ...It will give me 363 power , but conditions have to be great ...Normaly i use a focal reducer for a shorter focal length and a wider field of view ...By the way , meade says my scope has a theoretical power of 600 but i havent been able to pull it off ..
    16in Night sky
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    classic Big-mac , Meade eye pieces with a few odd balls thrown in ...
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    I sometime use the focal lenght of the objective lens or mirror divided by the eyepiece focal lenght in "inches". A 25mm eyepiece is "1" inch. 12.5 is roughly a "1/2 inch. I find I can do this in my head sometimes easier then millimeters. Certainly mm are accurate and I'm in no disagreement.

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    if i built a telescope with a focal length of 6 m, what focal length should the eyepeice have to give a magnification of 950 times? (hypothetically)

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    Welcome aubrie

    You would need about a 6.5 mm eyepiece.
    - A 6 meter focal length? Wow.

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    Hi Aubrie ...Welcome aboard the forums ...
    16in Night sky
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    I want to help
    Please ??
    If you build a telescope with a focal length of 1.3 m, what focal length should the eyepiece have to give a magnification of 100 times?
    this is Bonus Question please

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    A 13mm eyepiece.
    Enrico Bandolin
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