https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&feedformat=atom&user=Jdbaum 2026-05-24T07:29:19Z User contributions MediaWiki 1.30.0 https://www.explainxkcd.com/wiki/index.php?title=1791:_Telescopes:_Refractor_vs_Reflector&diff=134280 2017-01-27T14:26:56Z

<p>Jdbaum: /* Explanation */</p> <hr /> <div>{{comic<br /> | number = 1791<br /> | date = January 27, 2017<br /> | title = Telescopes: Refractor vs Reflector<br /> | image = telescopes_refractor_vs_reflector.png<br /> | titletext = On the other hand, the refractor's limited light-gathering means it's unable to make out shadow people or the dark god Chernabog.<br /> }}<br /> <br /> ==Explanation==<br /> {{incomplete|stub}}<br /> This comic shows two types of telescopes: {{w|Reflecting Telescope|Reflecting}} and {{w|Refracting Telescope|Refracting}}. It first looks like the comic is trying to show that refracting has many flaws, such as expense, size and visibility. However, the punchline invalidates these complaints with the (apparently major) flaw listed with the reflecting telescope: it can't see space vampires. The unstated reason for this is that vampires cannot be seen in a mirror. As space vampires do not exist {{Citation needed}}, this complaint is moot, and the reflecting telescope technically has no flaws in comparison to the refracting telescope. The title text expands on the seeing of supernatural beings, as another negative point is added to the refracting telescope- it apparently can't see shadow people or the Slavic god {{w|Chernabog}}, both of which are apparently equally important to the telescope's merit despite also not existing.<br /> <br /> An error in the comic would seem to be that both telescope illustrations contain a mirror (in the refracting, it's at the eyepiece). This would invalidate the advantage it has over reflecting.<br /> <br /> The title text adds an additional drawback to a refracting telecsope: it cannot see {{w|Shadow person|Shadow People}} or {{w|Chernobog|Chernabog}}. In reality, &quot;shadow people&quot; are a psychological phenomenon wherein humans ascribe human shapes and movements to shadows in dark spaces. Chernabog is a 12th century Slavic diety, whose name translates to ''black god''. His most famous apperance in modern media was in the 1940 Disney movie {{w|Fantasia (1940 film)|''Fantasia''}}.<br /> <br /> It is worth noting that in reality a Reflecting Telescope also has disadvantages compared to a refracting telescope. The main disadvantage is that in almost all reflecting telescope designs the focal point is directly in front of the mirror, i.e. in between the mirror and the target of interest. As a result a {{w|Secondary_mirror|secondary mirror}} is commonly used to direct the focal point somewhere outside of the field of view. However, this secondary mirror (and the struts that support it) will still block part of the field of view and result in diffraction patterns that also hinder the image quality. In fact, this is the source of the {{w|Diffraction_spike|diffraction spikes}} around stars which are commonly seen in astronomical images. Despite this disadvantage, reflecting telescopes are used almost exclusively in modern astronomy because of practical limitations in making large refracting telescopes.<br /> <br /> ==Transcript==<br /> {{incomplete transcript}}<br /> [The comic is one panel showing two different telescope designs.]<br /> REFRACTOR<br /> More expensive<br /> Less compact<br /> Chromatic aberration<br /> Reduced Light-gathering<br /> <br /> REFLECTOR<br /> Can't see space vampires<br /> <br /> Title text:<br /> On the other hand, the refractor's limited light-gathering means it's unable to make out shadow people or the dark god Chernabog<br /> {{comic discussion}}<br /> <br /> [[Category:Comics with color]]<br /> [[Category:Science]]<br /> [[Category:Astronomy]]</div>

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