Talk:Reflecting telescope

message: Where did the above information come from? Celestron is a company that makes telescopes, particularly schmidt-cassegrains. Perhaps this Celestron was something sold in other countries? I've just never heard of this telescope design and would be interested in seeing some documentation.
I moved User:172.158.63.83's question above from the article space Maksutov  paragraph to Talk here, and it's a good question; it sounds a lot like the Questar  as that was a Maksutov but I cannot get detailed specs of how the finder and main mirror were integrated. However Celestron also make a Maksutov design with a flip mirror, so I'm not sure. -Wikibob | Talk 12:10, 2004 May 20 (UTC)
I looked up Questar telescopes and found on Company 7's page a description
 that matches. I also looked up the Questar site . On Celestron's site I found . Basically, the paragraph in question could probably be clarified.... Elizabeth (User:172.158.63.83)kljuhugtft=ftrey
I modified the Maksukov reference to Questar... the flip mirror (it was really
a sliding prism)/"viewfinder" is covered in Questar's early 1950's patent, and
was (and still is) a  hallmark of the scope.  At $1000 (1957) then and today's
$4000 (for a 90mm diameter scope), it has forever been in the "luxury" class.
... Dick (User:128.95.100.19)
:I removed the section describing the Questar's built in finderscope - This article seems to specifically describe optical designs, not commercial brands. The Questar is not a separate design type and the Questar's addition of a built in finder has nothing to do with the Maksutov design.Halfblue 12:30, 17 September 2006 (UTC)
replies: text: I disagree. The questar design is another unique implementation, particularly the finder mechanism. Garglebutt / (talk) 23:07, 19 September 2006 (UTC)
replies: text: The page seems to be about unique optical designs and their variations. The section in question is about the Maksutov design. Questar's mechanical design of having the finder co-use the eyepiece with the main OTA is, as you say, a "mechanism", not a modification of the Maksutov optical design -- so it should not be listed as a Maksutov variation.Halfblue 03:48, 20 September 2006 (UTC)

text: it doesn't. Duk 08:53, 31 Dec 2004 (UTC)
thread_title:  Question on content for Celestron 

message: I believe that it is important to note that there is debate about whether Isaac Newton or Robert Hooke (http://en.wikipedia.org/wiki/Robert_Hooke) invented the reflecting telescope.  There appears to be no debate that Robert Hooke first demonstrated it, which should be noted in the reflecting telescope page.
Speisert 07:16, 8 December 2005 (UTC)
replies: text: Yes that should be added, if there is an authoritative article you can reference maybe there should be an opening sentence along the line of "There is some debate as to the origins of the reflecting telescope ". I have been cleaning up the recent adds coming in and moved it all into a "History" category. Those adds have no citations and if you take them at face value it states that Hook built the Gregorian design in 1673. That would mean that Newton built the first practical model in 1670. That section should probably be expanded to explain the limitations of early speculum metal and silver coatings that limited reflector design. 69.72.93.219 15:06, 16 December 2006 (UTC)
thread_title:  Newton or Hooke? 

message: Is a Dall-Kirkham a sub-variant of Cassegrain? Should it be moved up to be under Cassegrain?. I have a few pictures of "reflecting telescopes" that may work for a header picture in case the Ritchey 24" is too obscure. Halfblue 13:50, 20 September 2006 (UTC)
replies: text: For now I've readded this as there is no dall-kirkham article and I believe it is valid to reference novel implementations of designs and it appears to be in context for the article to me. Garglebutt / (talk) 06:29, 21 September 2006 (UTC)
replies: text: I have removed it again because the linked article astrograph states the Celestron f/6.8 astrograph does not exist and in fact Celestron has removed all info on it from their website. This is not the page to add information on commercially produced telescopes. This is a page on basic design. Wikipedia is not an indiscriminate collection of information WP:NOT. Wikipedia is an encyclopedia and edits should fit in an encyclopedic fashion. Commercial information should be added to their respective company pages or in a section in an article about commercial implementations of designs. I have also reverted edits by 165.138.178.3 since they were borderline vandalism. Halfblue 23:02, 21 September 2006 (UTC)
replies: text: Hmm! That is interesting. I don't agree with your view of what is valid content however the fact that this example no longer exists makes the point moot. I should also point out that neither of the oft quoted WP policy pages has anything to do with providing practical examples of theoretical concepts. Garglebutt / (talk) 23:15, 21 September 2006 (UTC)

text: And I've responded on your talk page. Garglebutt / (talk) 22:10, 22 September 2006 (UTC)
thread_title: More mods

message: :Nevertheless, the Gregorian design was used most commonly in practice for the next century and a half. Cassegrain designs then became more popular.
I rv-ed this edit because it does not make much sense in context. Gregorian design was used most commonly? For what propose? As compared to what? By who? Is there a citation to support this? What exactly are you trying to say here? Cassegrain designs then became more popular. More popular than what? Please clarify this statement and maybe add a citation before re-adding it. 69.72.7.161 01:59, 15 December 2006 (UTC)
thread_title: Gregorian notability

message: Could someone please explain "eyepiece"? Does an eyepece have to have lenses in it, and if so, what lenses and why?
Also - it's prety obvious that a system that throws an image onto a photographic plate or CCD isn't one yuo can look through - you can't just put your eye at the focal point. So what's the deal there?
:Hmmm... it did need a link to the article Eyepiece... fixed. That should contain answers to your questions. In general an eyepiece is a lens (more normaly a set of lenses) that magnifies the focal plane image and allows you to view it. 69.72.7.163 05:26, 2 February 2007 (UTC)
thread_title:  Eyepeice 

message: Perhaps the article should include mention of the Herscelian design, as a matter of historical curiosity. robert2957 12:21, 7 March 2007 (UTC)
replies: text: Added section. Fountains of Bryn Mawr (talk) 15:17, 23 February 2008 (UTC)
thread_title:  HERSCHELIAN 

message: There is a lot of info about Off Axis Newtonian Telescopes.
Essentially using a parabolic lens, shifted.  
Often cut from a larger parabolic "parent" lens.  
As far as I can tell, visual defects are limited to those inherited from the parent lens.  
The focal length would be identical as that of the parent lens, but for a smaller lens and thus may appear to have unusually long focal lengths for the actual size of lens.
Or if short focal length parent lenses are chosen, they often carry with them errors caused by the short focal length design.
DGM is one small manufacture of Off Axis Telescopes.
http://users.erols.com/dgmoptics/indexwelcome
The individual segments of many larger segmented Newtonian telescopes, for example the James Webb Space Telescope, are essentially equivalent to off axis Newtonian Telescope Mirrors.
--Keelec (talk) 09:06, 4 August 2010 (UTC)
thread_title:  Off Axis Newtonian 

message: The lower green line on the left is incorrect. It should be parallel to the upper green line on the left since these rays are coming from infinity. It should be lower than the mauve line. The result will be that the angles of incidence and reflection at the primary mirror are equal for both the green line and the mauve line. The only way for that to be true at the moment is for the two rays to have different normals at the mirror. - Peter  — Preceding unsigned comment added by 203.97.236.166 (talk) 22:22, 10 August 2015 (UTC)
thread_title:  Gregorian Telescope ray diagram 

message: :The use of mirrors avoids chromatic aberration but they produce other types of aberrations.
Forgive my noobity on the subject; but given that lenses are ground from a cylinder on one side wouldn't they fundamentally be forming a achromatic doublet, or achromatic lens? So wouldn't they be intrinsically by design incapable of causing chromatic aberration? For example: https://en.wikipedia.org/wiki/Achromatic_lens BaSH PR0MPT (talk) 18:46, 19 October 2015 (UTC)
replies: text: Sorry, don't follow. The linked article shows single element lenses are not achromatic (because they are fundamentally prisms, they make rainbows). Achromatic doublets are combinations of two pieces of glass, not a single chunk out of a cylinder, and they bring some colors together but are also not 100% achromatic. Fountains of Bryn Mawr (talk) 19:28, 19 October 2015 (UTC)
thread_title:  Chromatic aberration. 

message: The diagram of light rays in the Gregorian Telescope cannot be correct.  Someone has switched the green and purple segments in part of it.  — Preceding unsigned comment added by 23.119.204.117 (talk) 05:19, 19 February 2016 (UTC)
thread_title:  Gregorian incorrect 

message: This telescope type is classified as Catadioptrics type of telescope in some sources and sell as a catadioptric telescope https://www.bhphotovideo.com/c/product/1365511-REG/ioptron_6112_photron_8_200mm_f_8.html)( Gerçekler (talk) 04:37, 16 November 2021 (UTC)
replies: text: Advertisements are not reliable sources, for obvious reasons. Fountains of Bryn Mawr (talk) 18:29, 16 November 2021 (UTC)
thread_title:  Ritchey-Chretien Telescope 

message: This addition has no secondary sourcing to establish notability or even describe what it is. Patents and scientific papers are primary sources (see WP:PST) so need extensive secondary source coverage. This material also does not belong in an overview of Reflecting telescopes, there are a multitude of catadioptric lenses out there. Fountains of Bryn Mawr (talk) 11:39, 25 June 2022 (UTC)
thread_title:  Multi-reflecting telescopes