<story><title>First images from James Webb telescope exceed expectations</title><url>https://cosmosmagazine.com/space/exploration/first-photos-james-webb-telescope/</url></story><parent_chain><item><author>mysterypie</author><text>I was wondering why the star has 6 crisp points and found an explanation here (a 3 minute video):&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=VVAKFJ8VVp4&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=VVAKFJ8VVp4&lt;/a&gt;&lt;p&gt;The most interesting part of the video explains why even your naked eye viewing the sky at night will cause this effect -- it&amp;#x27;s due to imperfections in the lens of your eye.</text></item></parent_chain><comment><author>hatsunearu</author><text>I think the wikipedia explanation is much better.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Diffraction_spike&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Diffraction_spike&lt;/a&gt;&lt;p&gt;One deficiency is why apertures (effectively, the support structure in a telescope is an aperture) observe this behavior.&lt;p&gt;&amp;gt; No matter how fine these support rods are they diffract the incoming light from a subject star and this appears as diffraction spikes which are the Fourier transform of the support struts.&lt;p&gt;Like why is that the case?&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Airy_disk&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Airy_disk&lt;/a&gt;&lt;p&gt;Read this if you don&amp;#x27;t immediately understand why. This is the shape of the image you see when the aperture is circular. This is the Fourier transform of a circular aperture, which, in 1D, is a sinc function.&lt;p&gt;I can&amp;#x27;t give a straightfoward answer to elucidate further, but if you&amp;#x27;ve done signal processing stuff before you can probably handwavey explain that if there is a Fourier-transform relationship with one function, due to linearity and spacial invariance, you can say that it holds for all functions.</text></comment>
<story><title>First images from James Webb telescope exceed expectations</title><url>https://cosmosmagazine.com/space/exploration/first-photos-james-webb-telescope/</url></story><parent_chain><item><author>mysterypie</author><text>I was wondering why the star has 6 crisp points and found an explanation here (a 3 minute video):&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=VVAKFJ8VVp4&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=VVAKFJ8VVp4&lt;/a&gt;&lt;p&gt;The most interesting part of the video explains why even your naked eye viewing the sky at night will cause this effect -- it&amp;#x27;s due to imperfections in the lens of your eye.</text></item></parent_chain><comment><author>staindk</author><text>Good summary but I found it a bit weird how only 2 seconds were spent on the &amp;#x27;camera aperture&amp;#x27; explanation - as AFAIK that&amp;#x27;s the main cause for photos of stars and lights to have &amp;#x27;points&amp;#x27; - it depends on how many &amp;#x27;leaves&amp;#x27; (? term) your camera&amp;#x2F;lens aperture has -&amp;gt; the more leaves the &amp;quot;more-sided&amp;quot; a shape the aperture makes (hexagon, octagon...) thus the more points you get when photographing lights.</text></comment>