Talk:1791: Telescopes: Refractor vs Reflector

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search

Nitpick: The refracting telescope, drawn correctly, has a mirror in the optical path (image inverter), but it is made with a special vampire reflecting material Ichorium. (talk) (please sign your comments with ~~~~)

Doesn't the one in this image have a mirror too? at the bottom to make the image come out at the side instead of the end?

That's a good point: as drawn, the refracting telescope still has a mirror and also wouldn't be able to see space vampires. However, the refracting telescope doesn't have to have a secondary mirror, and there are plenty that don't, so it is more the drawing that is wrong rather than the text of the comic.Cmancone (talk) 14:31, 27 January 2017 (UTC)

Typically refractors use a prism rather than a mirror at the end, though it does the same thing. Can vampires be seen in a prism? 14:50, 27 January 2017 (UTC)

Only if they're pink. 14:57, 27 January 2017 (UTC)

Every time I press submit, it blocks me and makes me start over. Kynde, rather than making a small change every 30 seconds, perhaps you could do them all at once? -- Frankie (talk) 15:26, 27 January 2017 (UTC)

Well I'm sorry, I had the same problem as you. So I did not dare read it all through before I submitted, and thus so tried to fix the errors I found afterwards. That was also why I did not make the section for the real problems a subsection to the explanation so it (as the transcript) could be edited without conflicting with the other sections. --Kynde (talk) 15:30, 27 January 2017 (UTC)
Ah, it's network congestion. Sending small packets more quickly is indeed one way to get your message through, but it can lead to a tragedy of the commons. Everyone switching to larger packets is the optimal answer, but it's not a stable equilibrium. -- Frankie (talk) 15:39, 27 January 2017 (UTC)

Does anybody on the wiki HAVE a major in optics???? At least anybody who will see this page before MONDAY, when it will no longer be the latest??? That's right, Jacky720 just signed this (talk | contribs) 15:54, 27 January 2017 (UTC)

A telescope mirror typically would have no chromatic aberration, as it's a front-surface mirror. The light doesn't pass through the glass to get to the reflective material; the glass is on the back of the mirror for support. 16:15, 27 January 2017 (UTC)

I think where the commentary says "This means most reflector telescopes make do with narrow apertures" it should be "refractor telescopes". Rtanenbaum (talk) 16:18, 27 January 2017 (UTC)

FYI: Randall updated the comic, so that the refracting telescope doesn't have a mirror.-- 16:59, 27 January 2017 (UTC)

I would think that the main reason for Refractors over Reflectors is that it would be easier to make one with adjustable focus, so you would not need to wear glasses and – more importantly – you might be able to use the telescope as a binocular for things like birds. I don't know of any Reflectors with a significant adjustable focus, but I'm not an astronomer either. 17:31, 27 January 2017 (UTC)

Aren't there Space Vampires in Lovecraft somewhere? 22:48, 27 January 2017 (UTC) Not as such, but there are in the classic Queen of Blood [1] and in the unfortunate "Lifeforce" [2] . A refractor though should be able to see their interstellar umbrella [3] Anthony11 (talk) 07:05, 30 January 2017 (UTC)

An important advantage of refractors that keeps them popular is the very tiny amount of internal scattered light compared to reflectors. This really stands out when viewing planets and bright objects. Everybody loves that velvety black background field that refractors can provide. ExternalMonolog (talk) 09:59, 28 January 2017 (UTC)

Another issue with reflecting telescopes (though not pertinent to the joke) is that when used as a lens in photography, the bokeh, or unfocused highlights beyond the depth of field in an image, are rendered as circular 'doughnut' shapes, instead of the fuzzy points of light created by refracting lens systems. Run-on sentences, FTW. These Are Not The Comments You Are Looking For (talk) 01:20, 29 January 2017 (UTC)

Strictly speaking, bokeh is the "quality" of the OOF areas, not the areas themselves. Anthony11 (talk) 07:05, 30 January 2017 (UTC)

There can be no doubt that the original comic contains a *mirror*, not a prism. And a porro prism would not even work, because it reflects the projection by 180 degrees! Porro prisms are always used in pairs, to upright an image *without* changing the viewing direction! -- 12:26, 30 January 2017 (UTC)

The lens of a refractor flips the image, so having a single prism would render it upright. 01:48, 31 January 2017 (UTC)

These days, Chernobog may be better known as Czernobog, from Neil Gaiman's novel American Gods. 14:11, 1 February 2017 (UTC) Paul

Personal tools


It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal?