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  • Mirror vs prism diagonal?

    From StarDust@21:1/5 to All on Sat Sep 9 16:45:13 2023
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    🤗🤔

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From StarDust@21:1/5 to StarDust on Sat Sep 9 16:57:26 2023
    On Saturday, September 9, 2023 at 4:45:15 PM UTC-7, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    🤗🤔

    I already, had an older 11/4" prism diagonal, Celestron, Made in Japan.
    Just bought a mirror, dialectic diagonal coated, of the same size.
    I've been testing them in my 80 mm f/6.25 APO refractor daytime, lookin it trees, high power, low power, but can't see any difference?
    The prism type add focus distance, I have to to crank it out more for things to come into focused than the mirror diagonal.
    Any input, which one should I keep?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From W@21:1/5 to StarDust on Sat Sep 9 19:10:16 2023
    On Saturday, September 9, 2023 at 7:57:28 PM UTC-4, StarDust wrote:
    On Saturday, September 9, 2023 at 4:45:15 PM UTC-7, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    🤗🤔
    I already, had an older 11/4" prism diagonal, Celestron, Made in Japan.
    Just bought a mirror, dialectic diagonal coated, of the same size.
    I've been testing them in my 80 mm f/6.25 APO refractor daytime, lookin it trees, high power, low power, but can't see any difference?
    The prism type add focus distance, I have to to crank it out more for things to come into focused than the mirror diagonal.
    Any input, which one should I keep?

    Compare them on stars and planets. Daytime views have turbulence and low contrast that will hide defects.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From RichA@21:1/5 to StarDust on Tue Sep 12 00:33:55 2023
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    🤗🤔

    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From StarDust@21:1/5 to RichA on Tue Sep 12 04:19:46 2023
    On Tuesday, September 12, 2023 at 12:33:57 AM UTC-7, RichA wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    🤗🤔
    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance is a problem, some thing to think about?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Chris L Peterson@21:1/5 to All on Tue Sep 12 07:40:29 2023
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT), StarDust <csoka01@gmail.com>
    wrote:

    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    ??
    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance is a problem, some thing to think about?

    Prism diagonals do not make the light path longer. In fact, prism
    diagonals usually have a somewhat shorter light path.

    Prism diagonals will be slightly brighter which is a plus. They might
    introduce a small amount of chromatic aberration with short focal
    length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice any
    difference between the two, assuming they were quality products.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From StarDust@21:1/5 to Chris L Peterson on Tue Sep 12 14:49:30 2023
    On Tuesday, September 12, 2023 at 6:40:36 AM UTC-7, Chris L Peterson wrote:
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT),
    wrote:
    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    ??
    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance is a problem, some thing to think about?
    Prism diagonals do not make the light path longer. In fact, prism
    diagonals usually have a somewhat shorter light path.

    Prism diagonals will be slightly brighter which is a plus. They might introduce a small amount of chromatic aberration with short focal
    length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice any difference between the two, assuming they were quality products.

    In my experience comparing the two, using the prism diagonal, I have to crank the focuser out more to come into focus, using the same eyepiece, same OTA!
    I assume, my prism diagonal. Celestron, marked Made in Japan, should be a fairly good quality?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From W@21:1/5 to StarDust on Wed Sep 13 07:49:10 2023
    On Tuesday, September 12, 2023 at 5:49:33 PM UTC-4, StarDust wrote:
    On Tuesday, September 12, 2023 at 6:40:36 AM UTC-7, Chris L Peterson wrote:
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT),
    wrote:
    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    ??
    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance is a problem, some thing to think about?
    Prism diagonals do not make the light path longer. In fact, prism diagonals usually have a somewhat shorter light path.

    Prism diagonals will be slightly brighter which is a plus. They might introduce a small amount of chromatic aberration with short focal
    length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice any difference between the two, assuming they were quality products.
    In my experience comparing the two, using the prism diagonal, I have to crank the focuser out more to come into focus, using the same eyepiece, same OTA!
    I assume, my prism diagonal. Celestron, marked Made in Japan, should be a fairly good quality?

    The tube where the eyepiece fits could perhaps be a bit shorter on the prism diagonal, requiring that the assembly be moved outward to get to achieve focus. The prism could also be smaller than the mirror version.

    If the diagonal says "Japan" on it, I would keep it.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From StarDust@21:1/5 to All on Wed Sep 13 09:27:13 2023
    On Wednesday, September 13, 2023 at 7:49:13 AM UTC-7, W wrote:
    On Tuesday, September 12, 2023 at 5:49:33 PM UTC-4, StarDust wrote:
    On Tuesday, September 12, 2023 at 6:40:36 AM UTC-7, Chris L Peterson wrote:
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT),
    wrote:
    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust wrote:
    Which is better of the two?
    I read some where, mirror is better for short f ratio telescopes, f/6 and under, prism works better for longer f/ratios?
    ??
    I've never used a prism that was as good as a good mirror and I owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance is a problem, some thing to think about?
    Prism diagonals do not make the light path longer. In fact, prism diagonals usually have a somewhat shorter light path.

    Prism diagonals will be slightly brighter which is a plus. They might introduce a small amount of chromatic aberration with short focal
    length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice any difference between the two, assuming they were quality products.
    In my experience comparing the two, using the prism diagonal, I have to crank the focuser out more to come into focus, using the same eyepiece, same OTA!
    I assume, my prism diagonal. Celestron, marked Made in Japan, should be a fairly good quality?
    The tube where the eyepiece fits could perhaps be a bit shorter on the prism diagonal, requiring that the assembly be moved outward to get to achieve focus. The prism could also be smaller than the mirror version.

    If the diagonal says "Japan" on it, I would keep it.

    Thx!
    Think, I keep both.
    I also have an older 2" dielectric diagonal (William optics?), it's just too have on my 80 mm OTA to use 2" stuff.
    At F/6 it's all ready wide angle.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Brown@21:1/5 to StarDust on Thu Sep 14 08:08:14 2023
    On 12/09/2023 22:49, StarDust wrote:
    On Tuesday, September 12, 2023 at 6:40:36 AM UTC-7, Chris L Peterson
    wrote:
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT), wrote:
    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA
    wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust
    wrote:
    Which is better of the two? I read some where, mirror is
    better for short f ratio telescopes, f/6 and under, prism
    works better for longer f/ratios? ??
    I've never used a prism that was as good as a good mirror and I
    owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance
    is a problem, some thing to think about?

    Prism diagonals do not make the light path longer. In fact, prism
    diagonals usually have a somewhat shorter light path.

    +1

    Prism diagonals will be slightly brighter which is a plus. They
    might introduce a small amount of chromatic aberration with short
    focal length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice
    any difference between the two, assuming they were quality
    products.

    In my experience comparing the two, using the prism diagonal, I have
    to crank the focuser out more to come into focus, using the same
    eyepiece, same OTA! I assume, my prism diagonal. Celestron, marked
    Made in Japan, should be a fairly good quality?

    That isn't too surprising AOBE. What matters is the location of the
    optical surface where the reflection actually takes place.

    On a prism that is by total internal reflection off the glass surface
    right at the very back of the right angle prism assembly with perhaps a
    1mm air gap behind.

    For a front silvered optical flat mirror you have the physical thickness
    t of the mirror x1.4 extra length to the whole assembly when the
    reflecting surface is in the right position behind the scope.

    --
    Martin Brown

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From W@21:1/5 to Martin Brown on Thu Sep 14 07:22:22 2023
    On Thursday, September 14, 2023 at 3:08:20 AM UTC-4, Martin Brown wrote:
    On 12/09/2023 22:49, StarDust wrote:
    On Tuesday, September 12, 2023 at 6:40:36 AM UTC-7, Chris L Peterson wrote:
    On Tue, 12 Sep 2023 04:19:46 -0700 (PDT), wrote:
    On Tuesday, September 12, 2023 at 12:33:57?AM UTC-7, RichA
    wrote:
    On Saturday, 9 September 2023 at 19:45:15 UTC-4, StarDust
    wrote:
    Which is better of the two? I read some where, mirror is
    better for short f ratio telescopes, f/6 and under, prism
    works better for longer f/ratios? ??
    I've never used a prism that was as good as a good mirror and I
    owned Baader's best prism diagonal.

    Prism makes the light path longer, so if focusing travel distance
    is a problem, some thing to think about?

    Prism diagonals do not make the light path longer. In fact, prism
    diagonals usually have a somewhat shorter light path.
    +1

    Prism diagonals will be slightly brighter which is a plus. They
    might introduce a small amount of chromatic aberration with short
    focal length telescopes, which is a minus.

    In reality, in actual use, it is unlikely that you would notice
    any difference between the two, assuming they were quality
    products.

    In my experience comparing the two, using the prism diagonal, I have
    to crank the focuser out more to come into focus, using the same
    eyepiece, same OTA! I assume, my prism diagonal. Celestron, marked
    Made in Japan, should be a fairly good quality?
    That isn't too surprising AOBE. What matters is the location of the
    optical surface where the reflection actually takes place.

    On a prism that is by total internal reflection off the glass surface
    right at the very back of the right angle prism assembly with perhaps a
    1mm air gap behind.

    For a front silvered optical flat mirror you have the physical thickness
    t of the mirror x1.4 extra length to the whole assembly when the
    reflecting surface is in the right position behind the scope.

    None of that matters since the reflection occurs at a surface with an infinitesimally small thickness.

    It's the housing of the optic that determines how much back focus the device consumes.

    The OP is comparing just TWO such devices and can draw no general conclusions from that small sample.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)