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Thread: Telescope

  1. #1
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    Default Telescope

    Can someone suggest where to get a good 2X or so Telescope for 445nm.
    I do not really know much about the make up of a telescope, I know the basic function and that is about it.

    I am looking to half the beam size and double the divergence so I think a 2X is what I want.

    Thanks
    Larry

  2. #2
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    I have been working with Microscope objective lenses with some luck i will get a good formula.

  3. #3
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    If your happy with 2x magnification for both vertical and horizontal dimensions then you have two choices; a Keplerian or Galilean design. A Keplerian is simply two positive lenses in series with the ratio of the FL's determining the magnification ratio. To reduce the size of the beam place the longer FL first. The Galilean uses a positive and negative lens in series. In order to reduce the size of the beam place the positive lens first. Given the same focal ratios in either case (and in your case 2:1) use the longest FL that room permits ( a significant advantage of the more compact Galilean) this will give less off-axis aberrations and is a lot easier to align. If you want to experiment then a good source of cheep lenses is Anchor Optics (the low price division of Edmond Optics).

  4. #4
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    colimate to infinity? or umm close?

  5. #5
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    If you have some idea of your projection throw then collimate and align to that distance or a little beyond for the best performance. Only time an infinite throw would apply is for an aerial or extreme venue and then divergence is probably more forgiving anyway.

  6. #6
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    Quote Originally Posted by planters View Post
    If your happy with 2x magnification for both vertical and horizontal dimensions then you have two choices; a Keplerian or Galilean design. A Keplerian is simply two positive lenses in series with the ratio of the FL's determining the magnification ratio. To reduce the size of the beam place the longer FL first. The Galilean uses a positive and negative lens in series. In order to reduce the size of the beam place the positive lens first. Given the same focal ratios in either case (and in your case 2:1) use the longest FL that room permits ( a significant advantage of the more compact Galilean) this will give less off-axis aberrations and is a lot easier to align. If you want to experiment then a good source of cheep lenses is Anchor Optics (the low price division of Edmond Optics).
    I appreciate the help, I still do not know what type of lens to look for? I understand I need two lens but can you tell me what kind to search for. Do not know much about optics.
    Thanks
    Larry

  7. #7
    Join Date
    Dec 2007
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    Default

    Something like:
    NT47-370
    http://www.edmundoptics.com/products...owall#products

    and

    NT47-918
    http://www.edmundoptics.com/products...owall#products

    Distance between lenses would be around 48mm. Will give a fixed 2:1 beam reduction when aligned correctly. As planters said, the bigger distance between the two lenses the easier alignment will be.
    Change the lens diameters to match something that's a bit more practical if needed.

    You'll also need some nice fine adjustable mounts too

    Stanwax has some low price good ones for 15mm and 25mm optics:
    http://shop.stanwaxlaser.co.uk/adjus...ounts-21-c.asp


    Over and out
    - There is no such word as "can't" -
    - 60% of the time it works every time -

  8. #8
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    Hey Sir Briggs,

    is it DCX and DCV lenses or PCX and PCV ? ? ? I'm a bit confused
    "its called character briggs..."

  9. #9
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    Hello there!
    It shouldn't really make too much of a difference. Double's are better suited for low/near-unity relays.

    Use whatever set you have in your box of bits.
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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