The 7" Deluxe Intes I had had no problem showing smaller craters around the Apollo 11 Trio. None of these come with an interferometer test report, so it takes an experienced eye to be able to tell the difference. Yet I have also come across a 5" mass production scope that had no problem at all showing the trio (Collins 2.4km, Aldrin 3.4km but the most difficult of the trio to see). What is even more fascinating is the mass production technology has allowed for not only better average quality optics, but with this comes units that are thrown up that are stonking good too, reaching 1/6 wave and 1/8 wave! Rare, and in some instances not so rare either!Īs an example I have come across 8" mass production scopes that have been unable to even resolve the crater Armstrong from the Apollo 11 trio of craters (Armstrong is the largest of the trio at 4.6km). And would they be prepared to pay an extra premium for a modest % gain in resolution? Here's the thing, while most people don't know any better, for most applications better isn't necessary either and people are happy with what they get. And remember, most people don't know any better either.
#Diffraction limited free
But what are you prepared to pay for that longshot?īut why wouldn't scope companies provide such reports to verify the quality of their scopes? Because such quality cost money to generate and the test reports are not free either. They read "diffraction limited optics" and because they don't understand what this means then believe that this is somehow meaning "as good as it gets".
But most people don't know what such optics are capable of doing/providing. knowing what I know now about scopes, I wouldn't be putting my money towards a 1/4 wave scope now knowing what 1/8 and better optics gives me. If anything this allows for the quality of scope optics to be "legitmately" brought down. The term "diffraction limited" is a techy term that is misunderstood and used by some to push a line of supposed quality. Not hearsay from Intes as they provided an interferometer report with each of their instruments to prove their claim - something no other manufacturer has done or currently does. Their standard is remarkable in resolution capability, the Deluxe is outrageous in resolution capability! And these are all refined beyond the 1/4 wave. Their "Deluxe" offered 1/8 wave or better. Their "standard" was bewteen 1/6 and 1/8 wave. When you start using optics of known optical quality, these differences start becoming apparent. There is a marked difference in resolution between 1/4 wave and 1/8 wave, be it with point sources of light (stars) and extended objects. You then need to look through 1/8 wave optics. On the other hand, according to :Īny deviation from perfection results in energy transfer from central part of diffraction pattern to outer rings and potentially beyond resulting in a loss of contrast. Additionally, illustrates that the difference between a planetary image with 1/10th wave optics is nearly indistinguishable from 1/4 wave. I guess, for good measure, I'll throw in the oft-quoted Ceravalo star party test where folks could not distinguish between 1/4 wave and near perfect optics. An optical system in which the resolution is no longer limited by imperfections in the lenses but only by diffraction is said to be diffraction limited. In optics, the Airy disk (or Airy disc) and Airy pattern are descriptions of the best-focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. When the diffraction limit is reached, the lens is incapable of resolving greater frequencies A perfect lens, not limited by design, will still be diffraction limited. This limit is the theoretical maximum resolving power of the lens. Optics that bring all light rays to a focus within 1/4th of a wavelength of light of each other at the final focus are considered to be diffraction limited.Įvery lens has an upper-performance limit dictated by the laws of physics and the Airy disk, known as the diffraction limit. A telescope is said to be "diffraction limited" if its optics are made with enough accuracy so that all the light rays from a star fall within that star's Airy disk and diffraction rings, with no excess light being scattered out of theĭisc and rings by defects in the mirrors. My question is triggered by some of what I've come across below:Ī star appears in a telescope as a small Airy disk surrounded by faint diffraction rings. I am out of my depth in a puddle on this topic and could use some help answering this question.
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