PLate OPtimizer
Encyclopedia
PLate OPtimizer, or PLOP is a CAD program used by amateur telescope makers
to design primary mirror
support cells
for reflecting telescope
s. It was developed by telescope
maker David Lewis, first described in 1999, and used to simplify calculations needed in the design of mirror support cells. It was based on Toshimi Taki's 1993 program PLATE, with a simplified user interface, thus giving it wide acceptance among makers of large Dobsonian style amateur telescopes, with good support of mirrors as thin as two inches for a diameter of thirty inches.
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. 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 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 that merely results in refocus of a mirror's parabola
. PLOP can be used to calculate floating support points for a mirror's axial
(rear) support; however, additional tools are needed to calculate potential error from a mirror's lateral (edge) support
.
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.
Amateur telescope making
Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers build their instruments for personal enjoyment of a technical challenge, as a way to obtain an inexpensive or personally customized telescope, or as a...
to design primary mirror
Primary mirror
A primary mirror is the principal light-gathering surface of a reflecting telescope.-Description:The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal , or in later telescopes, glass or other material coated with a reflective layer...
support cells
Mirror support cell
In astronomy the mirror support cell - more commonly mirror cell - is the component of a reflecting telescope which supports the mirror in place to hold optical alignment, allow collimation adjustment, and protect it from falling out...
for reflecting telescope
Reflecting telescope
A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from...
s. It was developed by telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
maker David Lewis, first described in 1999, and used to simplify calculations needed in the design of mirror support cells. It was based on Toshimi Taki's 1993 program PLATE, with a simplified user interface, thus giving it wide acceptance among makers of large Dobsonian style amateur telescopes, with good support of mirrors as thin as two inches for a diameter of thirty inches.
Comparisons and limitations
A basic mirror cell may be built using minimal calculation and simple materials such as wood and outdoor carpet, with a good example being Dobson'sJohn Dobson (astronomer)
John Lowry Dobson is a popularizer of amateur astronomy. He is most notable for being the promoter of a design for large, portable, low-cost Newtonian reflecting telescopes that bears his name, the Dobsonian telescope. The design is considered revolutionary since it allowed amateur astronomers to...
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
Public domain
Works are in the public domain if the intellectual property rights have expired, if the intellectual property rights are forfeited, or if they are not covered by intellectual property rights at all...
program, Cell. 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 stress
Yield (engineering)
The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed...
. Although general finite element analysis programs such as Nastran
Nastran
NASTRAN is a finite element analysis program that was originally developed for NASA in the late 1960s under United States government funding for the Aerospace industry. The MacNeal-Schwendler Corporation was one of the principal and original developers of the public domain NASTRAN code...
will work for mirror cells, an advantage of PLOP is that it can be set to ignore deformation that merely results in refocus of a mirror's parabola
Parabola
In mathematics, the parabola is a conic section, the intersection of a right circular conical surface and a plane parallel to a generating straight line of that surface...
. PLOP can be used to calculate floating support points for a mirror's axial
Optical axis
An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens or microscope.The optical axis is an imaginary line that defines the path along which light propagates through the system...
(rear) support; however, additional tools are needed to calculate potential error from a mirror's lateral (edge) support
Lateral support
Lateral support may mean:* Lateral support, a type of support to help prevent sideways movement* Lateral and subjacent support, a legal term...
.
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
Honeycomb mirror
A honeycomb mirror is a large mirror usually used as the primary mirror in astronomical reflecting telescopes whose face is supported by a ribbed structure that resembles a honeycomb. The design provides sufficient rigidity for ultra-high precision optics while reducing the weight of the mirror...
s and those using active optics
Active optics
Active optics is a technology used with reflecting telescopes developed in the 1980s, which actively shapes a telescope's mirrors to prevent deformation due to external influences such as wind, temperature, mechanical stress...
systems are outside the design parameters of such programs.
See also
- Amateur astronomyAmateur astronomyAmateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
- Amateur telescope makingAmateur telescope makingAmateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers build their instruments for personal enjoyment of a technical challenge, as a way to obtain an inexpensive or personally customized telescope, or as a...
- List of telescope parts and construction
- MATLABMATLABMATLAB is a numerical computing environment and fourth-generation programming language. Developed by MathWorks, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages,...
- NastranNastranNASTRAN is a finite element analysis program that was originally developed for NASA in the late 1960s under United States government funding for the Aerospace industry. The MacNeal-Schwendler Corporation was one of the principal and original developers of the public domain NASTRAN code...
- Optical aberration
- Optical telescope#Imperfect images
- Whiffletree