PLate OPtimizer: Difference between revisions

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{{ otheruses4about|the CAD program, PLOP|the computer language conference group, PLoP|Pattern Languages of Programs}}

'''PLate OPtimizer''', or '''PLOP''' is a [[CAD program]] programused by [[Amateur telescope making|amateur telescope makers]] to design [[primary mirror]] [[Mirror support cell|support cells]] for [[reflecting telescope]]s. It was developed by [[telescope]] maker David Lewis, first described in 1999,<Refref>{{CitationCite journal| lasttitle = Lewis|Cures firstfor =Unsupportive DavidMirror Cells| author-linklast = http://www.davidlewistoronto.com/plop/Lewis| titlefirst = David| journal = Sky & Telescope| volume = | issue = June| pages = 132-135132–135| date = | year = 1999| url = | doivolume = 97| idbibcode = 1999S&T....97f.132L}}</Refref> and used to simplify calculations needed in the design of [[Mirror#Instruments|mirror]] support cells for [[telescope]]s.<Refref>{{cite web| last = Holm| first = Mark| authorlink = | coauthors = | title = Mirror Cells for Amateur Telescope Makers| work = | publisher = | date = | url = http://www.atmsite.org/contrib/Holm/Plop_optimized_cells/index.html| format = | doi = | accessdateaccess-date = May 3, 2009 }}

</Refref> It was based on Toshimi Taki's 1993 program PLATE,<ref>http://www.asahi-net.or.jp/~zs3t-tk/cell/cell.htm{{Dead link|date=July 2025 |bot=InternetArchiveBot |fix-attempted=yes }} Taki's brief intro to cell design</Refref>, however provideswith a simplified user interface, thus giving it wide acceptance among makers of large [[Dobsonian telescope]]s style amateur telescopes, with good support of mirrors as thin as two inches for a diameter of thirty inches.<ref>{{cite web| last = Anderson-Lee

| first = Jeff| authorlink =| coauthors = | title = Best of 18 and Over - A collection of plop cell designs

| work = | publisher = | date = | url = http://www.cs.berkeley.edu/~jonah/18plus/| format =| doi = | accessdateaccess-date = May 3, 2009}}</ref>

==Comparisons and limitations==

PLOP produces less mirror [[Yield (engineering)|stress]] than equal area rule calculation: it uses [[Finite element analysis]] and can be set to ignore [[Deformation (engineering)|deformation]] which merely results in refocus of the mirror's [[parabola]].<ref>[http://www.atmsite.org/contrib/Holm/Plop_optimized_cells/cellfaq.html#old Atmsite PLOP FAQ]</ref> It is useful to calculate floating support points for mirror [[Optical axis|axial]] (rear) support however additional tools are needed to calculate potential error from mirror lateral (edge) [[Lateral support|support]].<Ref>http://www.cruxis.com/scope/mirroredgecalculator.htm ''Cruxis'' site mirror edge support calculator tool</Ref> Additionally, PLOP calculations do not overcome error introduced by gluing the mirror to its cell, excessive tightening of edge supports nor impingement of the cell structure onto the mirror as result of differential cooling shrinkage. PLOP is not sufficient for the significantly more complex calculations arising from the support of large [[honeycomb mirror]]s nor those using [[active optics]] systems.<Ref>http://medusa.as.arizona.edu/lbto/tech/ua9502.htm Mirror Support System for Large Honeycomb Mirrors</Ref>

A basic mirror cell may be built using minimal calculation and simple materials such as wood and outdoor carpet, with a good example being [[John Dobson (astronomer)|Dobson's]] original telescopes. However, as amateurs sought to build larger and thinner mirrors, they found such designs inadequate.

Many amateur telescope makers use cells which are designed via [[equal area rule]] calculation, using programs such as David Chandler's [[public ___domain]] program, ''Cell''.<ref>{{Cite web| last = Chandler| first = David| title = Floatation Mirror Cell Design| url = http://www.davidchandler.com/cell.htm| access-date = 2009-06-21| url-status = dead| archive-url = https://web.archive.org/web/20090817122733/http://www.davidchandler.com/cell.htm| archive-date = 2009-08-17}}</ref> However, such calculation does not account for mechanical stresses introduced in one part of a telescope mirror by another part, whereas [[finite element analysis]] can be used to reduce such [[Yield (engineering)|stress]]. Although general finite element analysis programs such as [[Nastran]] will work for mirror cells, an advantage of PLOP is that it can be set to ignore [[Deformation (engineering)|deformation]] that merely results in refocus of a mirror's [[parabola]].<ref>[http://www.atmsite.org/contrib/Holm/Plop_optimized_cells/cellfaq.html#old Atmsite PLOP FAQ]</ref> PLOP can be used to calculate floating support points for a mirror's [[Optical axis|axial]] (rear) support; however, additional tools are needed to calculate potential error from a mirror's lateral (edge) support.<ref>http://www.cruxis.com/scope/mirroredgecalculator.htm ''Cruxis'' site mirror edge support calculator tool</ref>

Mirror cell calculations, whether using PLOP or another program, do not overcome errors introduced by gluing the mirror to its cell, excessive tightening of edge supports, nor impingement of the cell structure onto the mirror as result of differential cooling shrinkage. The significantly more complex calculations arising from the support needs of large [[honeycomb mirror]]s and those using [[active optics]] systems are outside the design parameters of such programs.<ref>{{cite web |url=http://medusa.as.arizona.edu/lbto/tech/ua9502.htm |title=UA-95-02: Mirror Support System for Large Honeycomb Mirrors |access-date=2009-11-20 |url-status=dead |archive-url=https://web.archive.org/web/20100703082028/http://medusa.as.arizona.edu/lbto/tech/ua9502.htm |archive-date=2010-07-03 }} Mirror Support System for Large Honeycomb Mirrors</ref>

==See also==

* [[Amateur astronomy]]

* [[Amateur telescope making]]

* [[List of telescope parts and construction]]

* [[MATLAB]]

* [[Nastran]]

* [[ReflectingOptical telescopeaberration]]

* [[Optical telescope]]

* [[Whiffletree]]

==Notes==

{{reflist|12}}

==External Resourcesresources==

* [http://www.cs.berkeley.edu/~jonah/18plus/p18.html A Study of 18-point Mirror Cell Optimization Using Varying Forces] Jeff Anderson-Lee, January 2003

* [http://www.davidlewistoronto.com/plop/ David Lewis, Automated Mirror Cell Optimization]

* [http://www.cruxis.com/scope/scope1100_mirrorcell.htm Mechanical design of the 110 cm cruxis telescope]

* [http://stellafane.org/misc/links.html Stellafane links page] {{Webarchive|url=https://web.archive.org/web/20210211175340/http://stellafane.org/misc/links.html |date=2021-02-11 }}

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[[Category:Computer-aided design software]]

[[Category:Finite element software]]