<p>No, it won't work. After all, it is recommended to make a pinhole camera to watch a solar eclipse. What you suggested is similar to a pinhole camera. Why it won't work, is that the rays that pass through the pinhole are not parallel, but divergent. Light from a point source would have (nearly) parallel rays.</p>

CC BY-SA 3.0
2014-06-09T13:42:44.413Z
Good point! But what about two pinhole cameras in a row? Only parallell light beams could pass through both. Would that turn sunlight into a point source? (Or are there other ways to do it?)
LocalFluff
CC BY-SA 3.0
2014-06-10T01:20:43.547Z
@LocalFluff Yes, 2 pinholes in a row should work. You could also mount a lens before the pinhole to produce parallel rays; it would have quite a long focal length.
LDC3
CC BY-SA 3.0
2014-06-10T17:51:19.440Z
So with such an arrangement, one could use the Sun as an arbitrarily large number of point sources, and thus focus its light at will?
LocalFluff
CC BY-SA 3.0
2014-06-10T18:25:39.017Z
@LocalFluff I don't understand your question. Parallel rays don't focus since there is no convergence. The only way to get many point sources is to have a lot of pin holes.
LDC3
CC BY-SA 3.0
2014-06-10T18:45:48.120Z
And I don't understand the physics/optics here. But I often read that sunlight cannot be focused well because it isn't a point source (so conversion to microwaves is prefered for transfering the energy, for example). I wonder if many point sources together could be better focused. And if so if the light from the disc of the Sun could be partitioned into many point sources.
LocalFluff
CC BY-SA 3.0
2014-06-09T13:28:30.637Z
2014-06-09T13:28:30.637Z
LDC3
<p>There's a limit to how well sunlight can be focused by a parabolic reflector or a lens because the Sun is not a point source. I wonder if the sunlight could be engineered to work as if it was (much more similar to) a point source.</p>

<p>If almost all of the Solar disc was covered by a coronograph, the light which gets through a small hole would be (almost) a point source. Is that correct?</p>

<p>If then an array of such covered reflectors or lenses concentrated their light to one and the same point, would a better focus be achieved than without covers?</p>

<the-sun><optics>
Can the Sun be used as a point source of light to achive better focus?
LocalFluff
# Can the Sun be used as a point source of light to achive better focus?

(Asked by: username_0 on 2014-06-09)

There's a limit to how well sunlight can be focused by a parabolic reflector or a lens because the Sun is not a point source. I wonder if the sunlight could be engineered to work as if it was (much more similar to) a point source.

If almost all of the Solar disc was covered by a coronograph, the light which gets through a small hole would be (almost) a point source. Is that correct?

If then an array of such covered reflectors or lenses concentrated their light to one and the same point, would a better focus be achieved than without covers?

**Tags:** the-sun, optics

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## 1 answers

### Answer by username_1 on 2014-06-09. Score: 2

No, it won't work. After all, it is recommended to make a pinhole camera to watch a solar eclipse. What you suggested is similar to a pinhole camera. Why it won't work, is that the rays that pass through the pinhole are not parallel, but divergent. Light from a point source would have (nearly) parallel rays.

> **Comments:**
> **username_0**: Good point! But what about two pinhole cameras in a row? Only parallell light beams could pass through both. Would that turn sunlight into a point source? (Or are there other ways to do it?)  
> **username_1**: @LocalFluff Yes, 2 pinholes in a row should work. You could also mount a lens before the pinhole to produce parallel rays; it would have quite a long focal length.  
> **username_0**: So with such an arrangement, one could use the Sun as an arbitrarily large number of point sources, and thus focus its light at will?  
> **username_1**: @LocalFluff I don't understand your question. Parallel rays don't focus since there is no convergence. The only way to get many point sources is to have a lot of pin holes.  
> **username_0**: And I don't understand the physics/optics here. But I often read that sunlight cannot be focused well because it isn't a point source (so conversion to microwaves is prefered for transfering the energy, for example). I wonder if many point sources together could be better focused. And if so if the light from the disc of the Sun could be partitioned into many point sources.  

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