Talk:Catadioptric system

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Problem with "aperture"?[edit]

Halfblue's recent change comment: "(→Photographic catadioptric lenses - "Aperture" is the problem word since it has two meanings-- the second being "diameter" of the Objective (optics). Catadioptrics do not come in one diameter.)" essentially for the phrase "but typically lack an adjustable iris and operate at a high fixed f-number equal to the focal ratio of the total optical system" to replace "but typically has a smaller ("slower") and fixed aperture"

I don't understand. Three problems here. First, what is the other meaning you're worried about? The aperture of this system is the diameter of the objective mirror; for any such device, it is typically fixed, not variable. Second, since the topic here is photography, why introduce the astronomical term "focal ratio" where you've just said "f-number"? Third, before we agonize too much over how to say it, is this even really true? Do catadioptric 500mm lenses have smaller apertures than 500mm lenses? And if so, why?

Dicklyon 03:00, 24 October 2006 (UTC)

I have reinstated most of this. Focal Ratio is not an astronomical term, it is a standard optical term for lenses, objective lens diameter (its aperture) divided into its focal length[1]. Fountains of Bryn Mawr (talk) 04:24, 7 April 2009 (UTC)


...And it has no color aberation, right? —Preceding unsigned comment added by (talk) 21:39, 17 March 2009 (UTC)

Name "Maksutov"?[edit]

Moved below to talk since claim of why they are called Maksutovs in un-referenced:

(although it is commonly credited to Maksutov, as it was popularized in 1954 by the US telescope seller Questar Corporation under the name Maksutov-Cassegrain). (talk) 20:42, 6 July 2009 (UTC)

I like your version better. I just tried to clean up previous version.Trilobitealive (talk) 03:02, 7 July 2009 (UTC)
Maksutov telescopes are called Maksutov telescopes becuase they use the specific design invented by Dmitri Maksutov (a single element auto-chromatic lens design not hit upon by Bouwers). Reworded article to fit that logical flow. Article could be reworded to beter describe these types as "meniscus" or "concentric" telescopes. More thoughts at Talk:Maksutov telescope#Maksutov and Bouwers. MrFloatingIP (talk) 03:22, 2 August 2009 (UTC)


This page needs more diagrams showing how the telescopes work to be comprehensible to the general public.

In what way? How a corrector works? Or how the mechanics of a Meade 8" Schmidt works? Or something in between? Fountains of Bryn Mawr (talk) 23:28, 4 April 2011 (UTC)


Today I was reverted by User:Fountains of Bryn Mawr when I added a note to the lede that a catadioptric optical system is also known as catadiopter or catadioptre. The edit summary read "unreferenced and seems to come up as a non-english term". Well, being unreferenced is not a valid reason to revert another editor unless the information is clearly incorrect. What I can say is that while the terms dioptric, catoptric and catadioptric systems or lenses are certainly much more common, I have occasionally run into the terms catopter and catadiopter (and their UK spelling variants) as well in books and papers in the past. Thinking about it, these might have been older sources, so it is possible that these are historical terms which are no longer in wide circulation today (however, this would not be criteria to not mention them in the article). Searching Google, I get a few hundred hits for them (including cites from books) in various languages including English. As the terms originate from ancient Greek, it is only normal to find derivations of them in various languages including English, French, Italian, Spanish and German. So, reliable sources (in English language) using the term catadiopter in the meaning of catadioptric optical system could be given. I cannot, however, come up with a source formally defining their equivalence - I guess authors just use(d) the term knowing what it means by having at least some minimum grasp of ancient Greek (as was common at least in Europe), so such a formal definition would have to come from another encyclopedia, perhaps a historical one. --Matthiaspaul (talk) 17:11, 23 July 2015 (UTC)

The revert was because it came up as a very uncommon synonym. "Catadiopter" only gets 15 useful hits in Google Books, some are vague about what they are describing and 8 hits are about corner reflector prisms (take a look at the nearest bicycle and the safety reflector on the back). Catadioptre gets 203 hits[2], but its a French term. If there is no "source formally defining the equivalence" it doesn't belong in Wikipedia. Fountains of Bryn Mawr (talk) 21:43, 23 July 2015 (UTC)
I didn't state there is no source "formally" defining it, I just don't have any such source handy. Actually, the fact that we both found the term in books (you in electronic books, me in printed ones in the past) indicates that the term exists and is used to mean a "catadioptic optical system" also in the English language, although it is apparently not very common (or no longer common, I don't know), but if we only include what's common, we can hardly achieve our goal as an encyclopedia. At least I expect an encyclopedia to mention synonyms.
If you check the German WP for de:Spiegellinsenobjektiv (catadioptric lens), it contains a sentence "Spiegellinsenobjektive, auch Katadiopter genannt, sind von astronomischen Teleskopen abgeleitet." (Catadioptric lenses, also called Katadiopter, ...) also indicating the equivalence of catadioptric lens and catadiopter. Another hint, that the term exists in the English language (and is apparently old) is our Diopter (disambiguation) page, stating that diopter also has the meaning of dioptric lens. If so, it is perfectly obvious from a linguistical point of view that the analogous term catadiopter existed as well, so we should mention it. --Matthiaspaul (talk) 10:48, 25 July 2015 (UTC)
Seeing a words used and including it in an article is WP:OR so we actually do need a definition somewhere and an indication that it is commonly used (beyond just our observations). Per WP:TECHNICAL we actually do mention what is common for a general audience. A very obscure word would not belong in a lead summary. That is not to say the word wouldn't show up in the body. Most of what we are seeing refers to prisms re: they can be refractive or reflective and refractive (catadioptric) depending how they are used ---> [3] and those are sometimes called catadiopter. The problem with even including it in the body is you need a source that says "Catadioptric is sometimes referred to as catadiopter. Fountains of Bryn Mawr (talk) 15:49, 25 July 2015 (UTC)
(I'm moving the comment you left on my talk page to where it belongs, the article's talk page) --Matthiaspaul (talk) 18:59, 26 July 2015 (UTC)
catadiopter or catadioptre
Hi, I reverted the addition[4] of "historically also known as catadiopter or catadioptre" because the statement is not supported by reference given, it is not a historical treatise on etymology and simply shows someone using one of the words. Wikipedia is not a dictionary where we see a word used and then try to come up with a definition and doing so is very much original research by Wikipedia standards. I have looked for a usable definition and have failed, it keeps coming up as a foreign language term or being used by what may be non-English speakers[5] (they may be misusing the word). At this point you really need to fulfill WP:BURDEN, i.e. citation to a reliable source that directly supports the contribution. Fountains of Bryn Mawr (talk) 18:36, 26 July 2015 (UTC)

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