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B Help with lenses for hand-made telescope

  1. Apr 25, 2016 #1
    I'm trying to make a handmade telescope, but I'm stuck with the lenses I bought 2 lenses. they are the same
    "convex from one side and concave from the other side" like glasses lenses.

    then I knew that I need a double convex for both the object lens and the eyepiece lens.
    so I decided to put the 2 lenses that I bought together to make a double convex lens so now air is in between the two lenses.

    Is what I did going to give me a double convex lens?!
  2. jcsd
  3. Apr 25, 2016 #2


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    Hello Mohab, :welcome:

    I'm afraid not. Unless you fill up the hollow space in beteen with glass too ...
    Did you check if the two lenses have positive or negative focal distance ? (positive: they work as a magnifying glass, negative: things look smaller but stay upright).
  4. Apr 25, 2016 #3
    Thanks for your reply BvU,

    I've looked up to the moon with it, the moon appeared smaller, I think it has a negative focal distance.
  5. Apr 25, 2016 #4

    Andy Resnick

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    meniscus lenses are fine to use; just be aware that the orientation does impact the total amount of aberrations.

    What are the focal lengths of the lenses?
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