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  • How much light does a refractor let through (in percentage)? 60% 70% 80

    From Jean Mario Charest@21:1/5 to All on Fri Nov 3 13:32:30 2023
    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.

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  • From Chris L Peterson@21:1/5 to ve2mcj@gmail.com on Fri Nov 3 15:55:36 2023
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest
    <ve2mcj@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.

    If it's a good quality refractor, I'd figure about 0.5% loss per
    air-to-glass surface.

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  • From StarDust@21:1/5 to Chris L Peterson on Fri Nov 3 18:54:08 2023
    On Friday, November 3, 2023 at 2:55:44 PM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per air-to-glass surface.

    So, it means a doublet refractor let's more light through than a triplet?
    🤔

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  • From W@21:1/5 to Jean Mario Charest on Sat Nov 4 03:12:14 2023
    On Friday, November 3, 2023 at 4:32:32 PM UTC-4, Jean Mario Charest wrote:
    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    For an old uncoated objective the number would be in the 85% range.

    For many modern coated objectives the number would be in the 95% range.

    The best anti-reflection coatings bring the number into the high 90s.

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  • From Chris L Peterson@21:1/5 to All on Sat Nov 4 07:11:58 2023
    On Fri, 3 Nov 2023 18:54:08 -0700 (PDT), StarDust <csoka01@gmail.com>
    wrote:

    On Friday, November 3, 2023 at 2:55:44?PM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest
    <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per
    air-to-glass surface.

    So, it means a doublet refractor let's more light through than a triplet?
    ?

    Depends on the design. Not all doublets or triplets have all of their
    surfaces facing air.

    --- SoupGate-Win32 v1.05
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  • From W@21:1/5 to StarDust on Sat Nov 4 19:14:35 2023
    On Friday, November 3, 2023 at 9:54:10 PM UTC-4, StarDust wrote:
    On Friday, November 3, 2023 at 2:55:44 PM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per air-to-glass surface.
    So, it means a doublet refractor let's more light through than a triplet? 🤔

    The triplet will probably have better coatings.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From StarDust@21:1/5 to Chris L Peterson on Sat Nov 4 19:23:03 2023
    On Saturday, November 4, 2023 at 6:12:05 AM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 18:54:08 -0700 (PDT),
    On Friday, November 3, 2023 at 2:55:44?PM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest
    <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per
    air-to-glass surface.

    So, it means a doublet refractor let's more light through than a triplet?
    ?

    Depends on the design. Not all doublets or triplets have all of their surfaces facing air.

    Your telescopes Chris are oil filled, isn't it?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Chris L Peterson@21:1/5 to All on Sun Nov 5 07:30:44 2023
    On Sat, 4 Nov 2023 19:23:03 -0700 (PDT), StarDust <csoka01@gmail.com>
    wrote:

    On Saturday, November 4, 2023 at 6:12:05?AM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 18:54:08 -0700 (PDT),
    On Friday, November 3, 2023 at 2:55:44?PM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest
    <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per
    air-to-glass surface.

    So, it means a doublet refractor let's more light through than a triplet? >> >?

    Depends on the design. Not all doublets or triplets have all of their
    surfaces facing air.

    Your telescopes Chris are oil filled, isn't it?

    I mainly image with an RC, so no lenses. I have a small refractor I
    use for occasional projects... a well corrected doublet, and I'm not
    sure of the details of the objective.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jean Mario Charest@21:1/5 to All on Sun Nov 5 06:25:08 2023
    Le samedi 4 novembre 2023 à 22 h 23 min 05 s UTC-4, StarDust a écrit :
    On Saturday, November 4, 2023 at 6:12:05 AM UTC-7, Chris L Peterson wrote:
    On Fri, 3 Nov 2023 18:54:08 -0700 (PDT),
    On Friday, November 3, 2023 at 2:55:44?PM UTC-7, Chris L Peterson wrote: >> On Fri, 3 Nov 2023 13:32:30 -0700 (PDT), Jean Mario Charest
    <ve2...@gmail.com> wrote:

    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    If it's a good quality refractor, I'd figure about 0.5% loss per
    air-to-glass surface.

    So, it means a doublet refractor let's more light through than a triplet? >?

    Depends on the design. Not all doublets or triplets have all of their surfaces facing air.
    Your telescopes Chris are oil filled, isn't it?
    Thank you for your advice. It's a 156mm achromatic doublet that I bought this spring. I didn't have the chance to observe with it. Also I want to buy a used Newton 200mm/1000mm f5.0 SkyWatcher but it doesn't have the cranford 10:1 just plain. but I doubt
    it needs to be coating on the primary mirror and the secondary mirror. How many years does a coating need to be redone?
    It seems to me to be an old model.... Do you have a price for this tube and also it has a small dovetail for an 8''!!!!

    --- SoupGate-Win32 v1.05
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  • From Rich@21:1/5 to Jean Mario Charest on Mon Nov 6 17:47:53 2023
    On Friday, 3 November 2023 at 16:32:32 UTC-4, Jean Mario Charest wrote:
    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.

    Depends on the frequency and the angle the light hits the lens at. Perpendicular rays of green light would loose about 0.5% per coated surface. So for an air-spaced triplet apo, about 3% or so. Light rays in blue or red end of the spectrum would lose
    more percentages and light hitting a curved lens at the edge (partially glancing blow) could lose as much as 20%.

    --- SoupGate-Win32 v1.05
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  • From StarDust@21:1/5 to Rich on Mon Nov 6 18:22:34 2023
    On Monday, November 6, 2023 at 5:47:55 PM UTC-8, Rich wrote:
    On Friday, 3 November 2023 at 16:32:32 UTC-4, Jean Mario Charest wrote:
    How much light does a refractor let through (in percentage)?

    60%
    70%
    80%
    90%
    Etc.
    Depends on the frequency and the angle the light hits the lens at. Perpendicular rays of green light would loose about 0.5% per coated surface. So for an air-spaced triplet apo, about 3% or so. Light rays in blue or red end of the spectrum would lose
    more percentages and light hitting a curved lens at the edge (partially glancing blow) could lose as much as 20%.

    What if I leave the cover on by accident?
    😃

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