lantern with a red shield

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jacdac

Senior Member
Lebanese
She should be able to see him by now. He always used a powerful lantern with a red shield to set up the Newtonian Reflector telescope on its mount, and get it aligned on the heavens.
Source: Crime on the Fens by Joy Ellis.
Context: It is night time.

What is a lantern shield? How does it look like?

Thank you.
 
  • Chasint

    Senior Member
    English - England
    I presume this was an old-fashioned lantern with a flame. If you are using a telescope then you do not want to have stray light from a lantern interfering with your vision. You need some kind of shield in order to block the lantern's light while you look through the telescope. Maybe this is a specially made shield for this purpose.

    It is probably a shaped piece of metal sheet that blocks the light when that is required.
     

    PaulQ

    Senior Member
    UK
    English - England
    It is probably a shaped piece of metal sheet that blocks the light when that is required.
    You're not an astronomer, are you? :D

    The shield is a screen.

    The description is one of collimating a telescope. The idea is that you shine a beam of light down a Newtonian telescope and the light then reflects inside the telescope and hits the red screen (red is chosen because of the optical properties of red light). The telescope is adjusted properly when the dot of light on the shield is sharp and central.

    You can look up "collimation" on the internet.

    collimate
    ˈkɒlɪmeɪt/
    verb
    gerund or present participle: collimating
    1. make (rays of light or particles) accurately parallel.
      "a collimated electron beam"
      • accurately set the alignment of (an optical or other system).
        "manuals give detailed instructions for collimating the optics"
     

    Chasint

    Senior Member
    English - England
    It is a screen. The description is one of collimating a telescope. The idea is that you shine a beam of light down a Newtonian telescope the light then reflects inside the telescope and hits the red screen (red is chosen because of the optical properties of red light). The telescope is adjusted properly when the dot of light on the shield is sharp and central.
    ...
    I bow to your superior knowledge.
     
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