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Prism Diagonal Anti Chromatic Aberration Effect?
I read that in a 90 degrees prism diagonal. Chromatic aberrations
are almost cancelled. I'd like to know to what extend it is true and what is the rule. For the entering light cone, it encounters flat surface via the air-glass interface, and since there is an angle of the incident light, chromatic deviation occurs from the splitting of the white light into the different wavelength inside the glass, But when the light cone exits on the other flat surface of the prism diagonal, the chromatic aberrations are cancelled from the opposite glass-to-air interface and the light cone returns to its original unchromatic aberrated form (this is assuming of course that the objective lens of the telescope is an apo or sct where chromatic aberrations are a nil compared to an achromat). Now what is the rule, like does shorter focal ratio or steeper light cone make the prism diagonal ineffective in cancelling the chromatic aberrations inside the prism diagonal? In long focal ratio scope or light cone entering and exiting a prism diagonal with parallel entry and exit surface (remembering that there is no chromatic aberrations from the internal reflections). How many percentage approximately of the light cone returns to its original unchromatic aberrated form after it exits the prism diagonal. If anyone has any site or articles about this in details. Let me know. Thanks. (Note: Some may say that a prism diagonal is obsolete and just buy a mirror diagonal. Well, the above inquiry is to understand better the behavior of chromatic aberrations in parallel entering and exiting surfaces such as a prism diagonal and novelty item like binoviewer (which has almost zero chromatic aberration when I observe thru one) and also to get some idea like how some products such as the chromacorr (which removes spherical aberrations) work. optidud |
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Prism Diagonal Anti Chromatic Aberration Effect?
I read that in a 90 degrees prism diagonal. Chromatic aberrations
are almost cancelled. Do you believe everything you read on the net? What you read is not true. Prisms do not cancel chromatic aberration, they just shift it a bit - more blue color error with a bit less red color error. Roland Christen |
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Prism Diagonal Anti Chromatic Aberration Effect?
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Prism Diagonal Anti Chromatic Aberration Effect?
This topic reminds me of the once sold 4" triplet "semi-apo" telescope kit, which in fact originated
from recycled Chinese border patrol giant binoculars. If the scope was not used with an appropriate optical length prism, the performance was rather mediocre. David |
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Prism Diagonal Anti Chromatic Aberration Effect?
While we're talking about prism diagonals, I have a question. With a commercial
prism diagonal (Celestron, for example)about how much light throughput is there to the eyepiece? Are these diagonals FMC or MC? Just wondering. I'm contemplating the purchase of a dielectric diagonal for use with my 8"SCT and 4"APO. Wondering if the extra bucks are worth it, aside from the durability factor that the dielectric diag. provides, Thanks in advance, Jeff |
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Prism Diagonal Anti Chromatic Aberration Effect?
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Prism Diagonal Anti Chromatic Aberration Effect?
Alan W. Craft wrote:
I'm wondering about whether to purchase Takahashi's 1.25" star diagonal (prism), or a William Optics 2" mirror diagonal to go with my FS-102. The reason I prefer refractors is that I like the idea of looking directly at an object rather than at a reflection of it. Hi Alan, The prism diagonal also uses reflection - looking is in no way more "direct" than when using a flat mirror. The back side of the diagonal is the mirror. - Alex I would be defeating that preference if I went with that reportedly superb mirror diagonal, but would be risking the introduction of spurious color, however small, with a prism. Of course, I could bypass both via a straight-through observance, but we are all well aware of its disadvantages, too. Opinions? Experiences? Alan |
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Prism Diagonal Anti Chromatic Aberration Effect?
I'm looking for shareware optical software in the net and there are many
of them, like Modas, Optalix, Atmos, Oslo, etc. Which of them has the easiest user interface that a novice can operate? I'd like to see ray trace of chromatic effects of light cone when it passes thru the Takahashi 1.25" prism diagonal, for example. I still can't visualize how the light cone behave from the dispersing lateral chromatic effects of a prism diagonal. Or if anyone can capture the screen and share the jpeg illustration. Pls. do. Thanks. optidud Alexander Avtanski wrote in message ... Alan W. Craft wrote: I'm wondering about whether to purchase Takahashi's 1.25" star diagonal (prism), or a William Optics 2" mirror diagonal to go with my FS-102. The reason I prefer refractors is that I like the idea of looking directly at an object rather than at a reflection of it. Hi Alan, The prism diagonal also uses reflection - looking is in no way more "direct" than when using a flat mirror. The back side of the diagonal is the mirror. - Alex I would be defeating that preference if I went with that reportedly superb mirror diagonal, but would be risking the introduction of spurious color, however small, with a prism. Of course, I could bypass both via a straight-through observance, but we are all well aware of its disadvantages, too. Opinions? Experiences? Alan |
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Prism Diagonal Anti Chromatic Aberration Effect?
On Mon, 14 Jul 2003 14:57:44 -0700, Alexander Avtanski ...reflected:
Alan W. Craft wrote: I'm wondering about whether to purchase Takahashi's 1.25" star diagonal (prism), or a William Optics 2" mirror diagonal to go with my FS-102. The reason I prefer refractors is that I like the idea of looking directly at an object rather than at a reflection of it. Hi Alan, The prism diagonal also uses reflection - looking is in no way more "direct" than when using a flat mirror. The back side of the diagonal is the mirror. - Alex I was waiting for someone to tell me that! Okay, so now I'm relegated to a straight-through observance! What a purist! I would be defeating that preference if I went with that reportedly superb mirror diagonal, but would be risking the introduction of spurious color, however small, with a prism. Of course, I could bypass both via a straight-through observance, but we are all well aware of its disadvantages, too. Opinions? Experiences? Alan Alan |
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Prism Diagonal Anti Chromatic Aberration Effect?
The reason I prefer refractors is that I like the idea of looking directly at an object rather than at a reflection of it. What's so wrong about looking at a 'reflection'....or actually 2 reflections when you count a secondary mirror...as compared to a severely 'bended cone of converging light'? (Which actually has a higher probability of introducing chromatic and spherical aberrations). Do you believe that a double reflected image is somehow not giving you reliable information?? Do you dis-believe your own reflected image in a mirror?? Just wondering if we, who use Newtonian reflector telescopes, are somehow missing something. Clear Skies, Tom W. |
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Thread | Thread Starter | Forum | Replies | Last Post |
Prism Diagonal Anti Chromatic Aberration Effect? | optidud | Amateur Astronomy | 12 | July 18th 03 04:25 AM |