Talk:Optical telescope

message: I have been cleaning up some of the telescope related articles (Reflecting telescopes, Catadioptric, Cassegrain reflector) (and seeking clarification via the web) and most references I am coming across state that there are "three basic types of telescopes: refractors, reflectors and catadioptrics". Is there a preferred nomenclature? i.e. are there three types (the third being catadioptric?) or are there only two types and a combination of the two (compound telescopes?) I am going to edit this article to fit what seems to be more prevalent but would appreciate any input.Halfblue 13:26, 24 September 2006 (UTC)
thread_title:  two primary types?

message: Look at:
http://en.wikipedia.org/wiki/Eyepiece
http://en.wikipedia.org/wiki/Eye_relief 
The distance between the eye (3) and the eyepiece (2) doesn't have to be equal 
to the eyepiece focal length "f2" so the diagram: "Keplerian telescope, schematic"
Should be corrected.  —Preceding unsigned comment added by 212.179.253.187 (talk) 21:00, 2 November 2007 (UTC)
thread_title:  Eye_relief - correction for the diagram "Keplerian telescope, schematic" 

message: I don't understand. We had a big thing about this over at the telescope article, yet he gives me trouble here. 1st, he asked for a reference (deleting a contribution in the process) then when I provided a reference, he changes his stance to "UNDUE" weight. Some people enjoy bothering and vandalising work, but it's not gong to make me quit. Nothing will. I will assume good faith and wait for a discussion to revert my arguement and references. Sincerely, InternetHero (talk) 02:05, 31 July 2008 (UTC)
replies: text: Exactly. The exact same problem that is happening over at telescope is happening now here. Material that is not specifically relevant to the optical telescope will be removed, unless there is a reliable source that mentions the optical telescope. DigitalC (talk) 04:34, 31 July 2008 (UTC)

text: Just because it is from the New York times does not mean it is a good reference. In fact, it isn't a good reference, because it barely mentions al-Haytham's contribution to the telescope. From WP:UNDUE, "Keep in mind that in determining proper weight we consider a viewpoint's prevalence in reliable sources". Even in the NY Times article, there isn't much weight to the assertation that al-Haytham was important to the development of the telescope. Ignoring the input of other editors is disruptive, and can lead to being blocked again. DigitalC (talk) 23:27, 31 July 2008 (UTC)

text: Yes, but there is only one sentence in the entire article about how his work led to the development of the telescope. - DigitalC (talk) 01:32, 1 August 2008 (UTC)

text: I agree, we are going in circles here. I have already discussed those references when you brought them up at Talk:Telescope#My_arguement_to_include_Ibn-Al-Haytham_.28Alhazan.29. DigitalC (talk) 02:09, 1 August 2008 (UTC)

text: Everyone has the right to edit Wikipedia, but they must follow the policies of Wikipedia when they do edit. You are correct that the sources you have found do not convince me that there should be any further mention of al-Haytham in the article. If you do not understand this, let me know and I can elaborate further on each of the sources. DigitalC (talk) 03:59, 1 August 2008 (UTC)
thread_title: DigitalC's reversions

message: The following section is a description of devices/performance and is redundant to those section covering that topic. They do not belong in history. Parts of it (if referenced) could be integrated into "How it works" or related subsections.
The resolution of Earth-bound telescopes is determined by seeing and not the diffraction limit.  One way around this problem is a space based telescope such as the Hubble space telescope.  However, space telescope are extremely expensive and of limited size, so adaptive optics for ground-based telescopes has been developed as well.  Other recent advances include segmented mirrors to allow larger diameters and active optics to compensate for gravitational deformation.
The following section has to do with the word "Telescope" and is already covered in the article Telescope. Radio, gamma ray, neutrinos, cosmic rays, and gravitational waves have nothing to do with Optical telescopes. The material on the derivations and usage of the word "Telescope" could (if referenced) could be integrated to expand the "Telescope" article.
Until the mid 20th century, all telescopes were optical, and were called simply 'telescopes'.  However, starting with the radio telescope, new devices to record emanations of different forms from the heavens were called telescopes as well.   Now the phrase 'optical telescope' (a retronym) is used for a telescope that gathers visible light, to distinguish it from telescopes of other types, ranging from other electromagnetic bands (radio through gamma ray) as well as other forms such as neutrinos, cosmic rays, and gravitational waves.
Fountains of Bryn Mawr (talk) 00:43, 5 December 2008 (UTC)
thread_title: Wrong section/article

message: Here are some potentially missing points, in no particular order:
*Reflecting telescopes were guided by theory, but the mirror technology is hard.  Note that the optics used in the Hubble were understood in 1632, and the mirror mis-manufactured in the 1980s.  The Hale (Palomar) 5 meter was the last big parabolic mirror, since Hale thought the project risky enough already.  All big telescopes since then are Ritchey-Chrétien telescope or more sophisticated yet.
*In comparison, theory did not help much with refractors, and in fact set them back. In particular, Newton thought an achromatic lens was impossible, and this discouraged research for many years.
*On the other hand, Newton invented the pitch lap, the key to polishing reflectors for the next few hundred years.
*In many cases there are three contributors, the person who first discovered it, the person who popularized it, and the person who made it work.  Cavalieri (1632) and Mersenne (1636) invented the Cassegrain and Gregorian reflectors, Gregory (1663) and Cassegrain (1672) made them popular (all before Newton's reflector) but could not make them work, but later Hooke (1674, Gregorian) and (???, Cassegrain)  figured out how to make the mirrors and make them practical.
*Many modern telescopes are optimized for etendue as well as diameter.  For many research programs, field of view is as important as mirror size (since in a large angle investigation or survey, one can be traded for the other.)
*Modern telescopes have no need to accomodate a human observer at the focus, though this was a requirement for many years.
:Those look like important points that could be added to the article.  Why not  give it a go, be bold.   Martin Hogbin (talk) 19:19, 20 December 2008 (UTC)
thread_title:  Some big picture points 

message: I reworked the History section for prose style, focus, and to fit summary style and other guidelines. Also several misstatements of fact or mis-quotes of reference. Several referenced sections were a bit to detailed for a summary of telescope history but should be added to History of the telescope.
RM first statement since it is a statement of fact that is un-referenced WP:V, not invention of "science” by referenceFred Watson, Stargazer (page 55) . Removed single thinker examples “Archimedes”, “Alhazen” ect, references do not specifically say this WP:V, citing one person per each era is back to WP:UNDUE. Alhazen as first to put "Optics on a scientific footing" is a misreading of King and contradicted by ref .  Powers as a source is unreliable as used since it should not be used for statements of fact WP:RELY.
Summery of introduction of achromatic lenses was missing.
Statement “Theory was of little help in the development of refractors” is broad, redundant to intro and was a quote referring to Hyperbolic lenses, a bit off topic to the purpose of a summery. No reference as to how an Aspheric lenses is an important summery step in the history of telescopes so reworded. These should be added to HOTT if they can be put into historical context.
Reflecting telescopes were known almost from the refractors invention
Watson says Bonaventura Cavalieri had theories similar to Cassegrain and Gregorian, he did not intend them as telescopes, and they were not “known by 1632”, they were, in fact, known by 1975, and citation of Bonaventura Cavalieri is more of a footnote to history of telescopes than a summery “fact” (WP:RELIABLE). Should be added to HOTT if it can be put into historical context, if any.
James Short did not make the first parabolic mirrors, just perfected fabrication. Parabolic mirrors were being used in Gregorian telescopes being built by Robert Hooke in 1673 
In a summery, Newton’s contribution would be a working reflector, not the pitch lap and source says he my not have invented it. 
Schmidt Cassegrain is a commercial subgroup of the real invention, the Schmidt camera. Schmidt cameras were not invented so the corrector could to support the secondary, in fact they don’t in research telescopes, and dust seal was not a priority, they were invented for wide field work.
Fountains of Bryn Mawr (talk) 03:41, 18 January 2009 (UTC)
thread_title: Corrections

message: Science, of the AAAS, has produced a cartoon version of the history of the telescope.  It's at A brief history of the telescope by Larry Gonick and William Alschuler.  It makes many of the same points we do, although there is more on achromatic lenses and less on reflectors.  The people mentioned at Alhazan, Lippershey, Janssen, Galileo, Kepler, Gregory, Newton (including his error about achromatic lenses), Hall, Bass, Dollond, Hershel, Rosse, Hale, Schmidt, (then segmented mirrors and adaptive optics with no names).  
Although their has more humor (about ridiculously long refractors, and the folly of siting telescopes in Ireland) I think the version here (at least in some incarnations) has more info in the same or less space.
What does everyone else think??  LouScheffer (talk) 00:58, 19 January 2009 (UTC)
replies: text: That article seems to be subscription only (at least I can't get to it:(). FYI there is a whole series of videos on the topic at the Institute and Museum of the History of Science. They give a basic outline and bring up room for improvement (they show a second inventor for mirror silvering, ect) and other milestones. It may not pertain to this summary article, except for some changes in the footnotes, but it looks invaluable for History of the telescope. Fountains of Bryn Mawr (talk) 15:47, 21 January 2009 (UTC)
replies: text: I tried this again.  You are right, it's subscription.  I did not notice since at work we have an institutional subscription, automatic by IP address, I think.  I suspect most schools or research institutions will have this.   From home I needed to use my AAAS membership to see the article (if you are a AAAS member then you can get digital access at little or no charge..)   LouScheffer (talk) 13:46, 23 January 2009 (UTC)
thread_title:  History of the telescope in magazine 'science' (cartoon version) 

message: * Redirect to Optical telescope - Clearly a duplicate article. Some ref'ed material could be merged. Fountains of Bryn Mawr (talk) 16:01, 14 April 2009 (UTC)
replies: text: It's not worth a discussion, as it's just a recent inadvertant content fork; just redirect it here and tell the author to put anything new here instead. Dicklyon (talk) 02:12, 15 April 2009 (UTC)
thread_title: [[Visible spectrum telescopes]] merger

message: The invention of the telescope can be seen as the first door that was opened to more information about Space. In the Wikipedia article, “Optical Telescopes,” the writers go into the specific history of the optical telescope. The history section has a plethora of information regarding the telescope. One of the most striking comments within the article was on the first line, which states, “The telescope is more a discovery of optical craftsmen than an invention of scientist.” This comment was well stated, because it shows that technological development does not have to come from those within the specific field of study of the technology. For example, the optical telescope, according to Wikipedia, was credited to a pair of spectacle makers. In addition, the writing talks about who the inventors of the telescopes where and even around the time period that the telescope was invented. Moreover, the piece referred to the additional people that improved upon the design of the telescope, like Galileo and Johannes Keppler. The article goes on to describe how the optical telescope was the gateway to other telescopes, like the refracting telescope.  The last part of the writing refers to how the optical telescope led to the development of other telescopes, like the refracting telescope.
While the article was easy to read, there were a few issues with the grammar and format of the piece. One such instance of a grammatical error was within the first paragraph of the history section. It reads, “The lens and the properties of refracting and reflecting light had been known since antiquity and theory on how they worked were developed by ancient Greek philosophers, preserved and expanded on in the medieval Islamic world, and had reached a significantly advanced state by the time the telescope’s invention in early modern Europe.” The sentence is long-winded and wordy. In addition, the sentence does not flow and has some grammatical issues. Instead of saying “and theory on how they worked were developed,” the sentence should read, “and the theory on how it worked was developed.” This is not only grammatically correct, but it also helps the sentence flow. Furthermore, about half of the article refers to how the optical telescope aided in the development of other types of telescopes. In my opinion, the article should have spent more time talking about the invention than the overall impact of the telescope. It makes the section shift from a historical section to an impact or result section. 
Overall, the history section has absolutely no pictures in the historical section of the article. Instead of having no pictures, the article could have placed pictures of the historical figures that helped aid in the invention or advancement of the technology. For instance, a picture of Galileo could be used, because he was the first to use telescope for astronomical reasons. Another picture that would be useful within the writing would be a picture of an older model of the telescope. This could help viewers picture what the telescope originally looked at. Besides pictures, the article could also use more dates. There are only a few select dates and some are broad like the 13th century. Finally, the historical section alone has 19 citations. Most of these citations are from websites, like the “Galileo Project” And “MadeHow.com.” There are a few good secondary sources, like books, but some of the sources are dated as far back as 1975. If more information could be found on the telescope in current secondary sources, instead of websites and outdated writings, then the historical section would be more credible as a source of information. 
When comparing the Wikipedia article about optical telescopes to the Encyclopedia Britannica article, within the first sentence there were discrepancies between the two. Britannica gives the credit to Galileo as building and using the first telescope for astronomical use, but does not mention the two spectacle makers from the Wikipedia article. The article is also more specific with dates and has the measurements of various telescopes. Furthermore, the article goes into more detail about what the telescope was able to see, like some of the planets. Similarly to the Wikipedia article, Britannica does not have any pictures within the section, but one the left hand side of the website, there is a photo galaxy with several images of telescopes.  — Preceding unsigned comment added by HIST406-11rcaouett (talk • contribs) 03:29, 5 October 2011 (UTC)
thread_title:  Optical Telescope Critique 

message: I removed the list "Famous optical telescopes" per WP:LIST (can be seen here) because the list's inclusion criteria is undefined - all optical telescopes listed in Wikipedia are "Famous" (notable) - to pick some as more famous seems to be against WP:NPOV. There may be a way to re-include the list with a non-POV definition/inclusion criteria so editors won't be guessing what should be in the list, but I don't see one. The list may simply be redundant/unnecessary since "See also" section already has links to all definable lists. Fountains of Bryn Mawr (talk) 19:19, 26 June 2012 (UTC)
thread_title: Famous optical telescopes?

message: I'm considering putting a few characteristics under a single heading with the characteristics as sub-headings (also expanding more specific information), these properties include;
* Focal length and f-ratio
* Light-gathering power
* Magnification
* True FOV vs. apparent FOV
Is anyone against a cleaner layout and more informative specific optical telescope properties? Dr.Smash 14:29, 9 December 2013 (UTC)
replies: text: Looks good. I was noticing for a while that this article seems to be missing "Magnification", the first thing a reader would probably want to know. FOV was a good add as well. The section "Focal length and f-ratio" should probably be "Focal length and focal ratio" since focal ratio is the correct term and Wikipedia asks that full words be used before abreviations. Fountains of Bryn Mawr (talk) 17:23, 9 December 2013 (UTC)

text: I have sent a request to Starizona, a source for a large part of the magnification information, for the permission to use their images. These are great examples of diffraction and image quality which I really think the topic deserves and provides the most accurate display of factors which I could find on a short basis. Dr.Smash 03:55, 10 December 2013 (UTC)

text: I may have gone a bit overboard with specific information and really require some input on the vastness of information which could be included and what not to. The information can easily be placed elsewhere however it directly relates to the optical performance and capabilities of optical telescopes, the wiki pages where it could be placed don't originally contain the information.</br>The topics in question refer to the characteristics; further information on minimum, maximum, optimum and wide-field magnification with more specific formula (they are only standardized at the moment), eyepiece focal length and formulas relating with how it affects the other characteristics and viewing capabilities, determining maximum performance from the telescope using the correct accessories, more information on exit pupil relations, magnitude limits and expansion in light gathering power. More information can be found at rocketmime.com/astronomy. I would imagine the first stop for someone wanting information would be directly to the telescope page, rather than ciphering through various articles on viewing performance, this is where the usefulness comes in. I will add some info into my sandbox while hopefully we can make an informed decision about what information can be included. Dr.Smash 08:19, 10 December 2013 (UTC)
thread_title:  Amalgamation of properties 

message: A quick note of the reference equations used in many of my content additions, I tried to cite the equations without using the same values used in them. Such values are based on approximations, eg. Moon values are referenced from the Wikipedia Moon characteristics rather the supplied values on the reference page. In some cases a mean value was used in place of an approximation, such as Earth-Moon distance or angular diameter. This gives a more precise syntax where a user can directly reference values from within Wikipedia to achieve the same results. The overall effect just means that some of the values don't match cited references, however the equations do. Dr.Smash 02:23, 18 December 2013 (UTC)
thread_title:  Formulae citation 

message: Dark glass is not safe enough, see Arc welding lenses, see Telescope solar lenses.
was added as correction
Please either say nothing, refer to manufacturer instructions, or correctly say it is a special solar lense. Dark glass alone will cause blindness over time.
This is also true for cheap* sunglasses but don't tell anyone!
(Cheap sunglasses use dark material and the eye feels safe but is actually being damaged at wavelengths that do not cause pain. A doctor would suggest squinting eye lids instead of relying on cheap sunglasses for eye pain situations)
Never look at arc welding using dark sunglasses.  — Preceding unsigned comment added by 72.219.202.186 (talk) 14:51, 9 April 2014 (UTC)
thread_title: Lenses and Filters

message: Isn't this diagram utterly useless?
It completely lacks clear labelling,and for the life of me,I can't figure out what difference between the red and black lines are.
Perhaps it should be clearly labelled,so the people who lack knowledge about telescopes(i.e,your target audience) should be able to gain knowledge about telescopes.
As it is now,I think it is quite useless.182.181.152.111 (talk) 06:33, 28 April 2014 (UTC)
thread_title: Schematic of a Keplerian refracting telescope

message: I found no evidence in the OED, in Wiktionary, or elsewhere that either "everted" or "reverted" means "reversed left to right". Maybe I read the entries too hurriedly. Is there another source?
It confusing to say that "telescope designs produce an inverted image" and at the same time "the image is both inverted and reverted". This gives "inverted" two incompatible meanings, one of which is defined as the other plus something else. While it could be argued from dictionary entries that "inverted" could mean either of these, the reader should leave with only one meaning for this technical term in the telescope context. 129.132.209.199 (talk) 23:42, 7 June 2014 (UTC)
thread_title:  Inverted, everted 

message: Should it be mentioned somewhere that optical telescopes are afocal systems? Shmayo (talk) 13:29, 12 March 2015 (UTC)
thread_title:  Afocal system 

message: Hi folks.  As an astronomy professor, I thank you all for your contributions to making this article better.  I made a change in the introduction, to clearly state the proportionality between a telescopes aperture and its light gathering power and its resolving power.     Resolving power, as previously stated in the article is "directly proportional" to aperture, in the mathematical sense:
https://en.wikipedia.org/wiki/Proportionality_(mathematics)#Direct_proportionality
Light gather power of course is proportional to a telescope's area, and thus to at the size of its aperture *squared*, as state later in the article.  
Substar (talk) 17:25, 20 September 2019 (UTC)
thread_title: "Directly proportional"