# Aragoscope

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{{Short description|Proposed occulter}}
An '''Aragoscope''' is a telescope design based on diffraction around the edge of an occluding disc, named after French scientist [François Arago](/source/Fran%C3%A7ois_Arago).

==Concept==
The light diffracted around the edge of a perfectly circular occluder interferes constructively at the central axis, producing a bright spot known as the [Arago spot](/source/Arago_spot).  The resolution at that point would be equal to the resolution of a conventional lens with the same size as the occluder, although the light would be much less intense.<ref>{{cite web |title=Phase 1 Report to NIAC for The Aragoscope: Ultra-High Resolution Imaging at Low Cost |url=https://www.nasa.gov/sites/default/files/atoms/files/2014_phase_i_webster_cash_the_aragoscope.pdf |website=[NASA](/source/NASA) |date=2016-09-26 |archive-url=https://web.archive.org/web/20230207020837/https://www.nasa.gov/sites/default/files/atoms/files/2014_phase_i_webster_cash_the_aragoscope.pdf |archive-date=2023-02-07 |url-status=live |last1=Cash |first1=Webster |last2=Harness |first2=Anthony |last3=Shipley |first3=Ann |last4=Zeiger |first4=Ben}}</ref> On this basis it would be possible to create a telescope by placing a suitable disc in space accompanied by a separate telescope some distance away along its axis. This concept has been explored by NASA and received Phase One funding in June 2014 by the [NASA Innovative Advanced Concepts](/source/NASA_Innovative_Advanced_Concepts) (NIAC) program.<ref>{{cite web|title=The Aragoscope: Ultra-High Resolution Optics at Low Cost|url=https://www.nasa.gov/content/the-aragoscope-ultra-high-resolution-optics-at-low-cost/#.U5givlKSz8s|website=NASA|accessdate=9 February 2017}}</ref><ref>{{cite web|url=http://www.colorado.edu/today/2015/01/23/new-space-telescope-concept-could-image-objects-far-higher-resolution-hubble|website=CU Bolder Today|accessdate=9 February 2017|title=New space telescope concept could image objects at far higher resolution than Hubble}}</ref>

It is important to note that this is a very different approach from that taken by another NASA project, the [New Worlds Mission](/source/New_Worlds_Mission), which aims to use an occluder with "petals", otherwise known as a starshade, specifically designed to ''avoid'' diffraction onto the central axis.

==See also==
*[Arago telescope](/source/Arago_telescope), a 38&nbsp;cm (15 inch) refractor at Paris Observatory's east tower
*[Zone plate](/source/Zone_plate)

==References==
{{reflist}}

Category:Telescopes

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Adapted from the Wikipedia article [Aragoscope](https://en.wikipedia.org/wiki/Aragoscope) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Aragoscope?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.