DEFINITION OF TERMS GLOSSARY M-N Telescopes, Binoculars, Spotting Scopes, Microscopes, Riflescopes, Astronomical Accessories,Refractor,Reflector,Monoculars,Night Vision,Cassegrain,GPS,Optical Tubes,Digital Camera,Eyepiece,Filters,Barlow,Lenses,Diagonals,Prisms,Tripods,Mounts,Finder Scopes,BinoViewers,Optics,Astronomy,Astrophotography,Laser Range Finders,Rangefinders, Low Price
Secure website, verified, safe for online shopping
The World's Largest Selection of Optics for Astronomy, Sport, Science and Education
Shop By Price
Shop By Interests
Gift Certificate

 


DEFINITION OF TERMS (GLOSSARY): M - N

  Scope City's Optics Crash Course
Tell Friend  

M

Magellanic Clouds Two small, irregular galaxies found just outside, and orbiting, our own Milky Way galaxy. The Magellanic Clouds are visible in the skies of the southern hemisphere.

Magnetic Field A condition found in the region around a magnet or an electric current, characterized by the existence of a detectable magnetic force at every point in the region and by the existence of magnetic poles.

Magnetic Pole Either of two limited regions in a magnet at which the magnet's field is most directional.

Magnification A measurable increase in the apparent size of an object. Magnification = (focal length of a telescope) / (focal length of the eyepiece).

Magnitude The degree of brightness of a star or other object in the sky according to a scale on which the brightest star has a magnitude -1.4 and the faintest visible star has magnitude 6. Sometimes referred to as apparent magnitude. In this scale, each number is 2.5 times the brightness of the previous number. Thus a star with a magnitude of 1 is 100 times brighter than on with a visual magnitude of 6. This scale is a modern derivation of the ancient astronomer Ptolemy, who divided the stars in the sky into 6 magnitudes, the brightest being "First", and the dimmest "Sixth". The smaller this number is, the brighter is the object or star.

Main Belt The area between Mars and Jupiter where most of the asteroids in our solar system are found.

Major Planet A name used to describe any planet that is considerably larger and more massive than the Earth, and contains large quantities of hydrogen and helium. Jupiter and Saturn are examples of major planets.

Mak - Maksutov-Cassegrain Telescope

Maksutov-Cassegrain - A catadioptric telescope design characterized by a thick deeply curved Corrector Plate , all-spherical mirrors, and usually an f15 focal ratio.

Maksutov-Newtonian: a telescope comprising a meniscus corrector, concave primary, and flat secondary, assembled into a Newtonian configuration. Exhibits coma, though not as much as a Schmidt-Newtonian.

Marechal's Criterion In optical systems, the final wave front aberration tolerance of 0.25-wave peak-to-valley and 0.07-wave(1/14) root-mean-square. Similar to the Rayleigh Limit, but also specifies a smooth wave front.

Mass A measure of the total amount of material in a body, defined either by the inertial properties of the body or by its gravitational influence on other bodies.

Matter A word used to describe anything that contains mass.

Meridian An imaginary circle drawn through the North and South poles of the celestial sphere.

Mesopic - a condition of the eye where the ambient light is starting to turn the cones in the eye¡¯s retina on and we have partial color vision. Most people have this when looking at the night sky after becoming completely dark-adapted..

Messier Object - A non-stellar celestial object listed in the Messier Catalog, compiled in the 18th Century.

Meteor A small particle of rock or dust that burns away in the Earth's atmosphere. Meteors are also referred to as shooting stars.

Meteor Shower An event where a large number of meteors enter the Earth's atmosphere from the same direction in space at nearly the same time. Most meteor showers take place when the Earth passes through the debris left behind by a comet.

Meteorite An object, usually a chunk or metal or rock, which survives entry through the atmosphere to reach the Earth's surface. Meteors become meteorites if they reach the ground.

Milky Way - Our home galaxy. We see it at night as a circle of faint light that goes 360 degrees around the sky. It is only visible in a dark sky.

Minor Planet - Another name used to describe a large asteroid.

Minus Violet Filter - a filter that removes the color of light most poorly focused by a two-element achromatic refractor lens - violet.

Mirror Coatings - Aluminum or dielectric coatings deposited on first-surface mirrors to greatly enhance reflectivity.

MN - Maksutov-Newtonian Telescope

Monocentric: a term referring to a lens set which has their radii of curvatures at the same location, or at nearly the same location. Also refers to an early type of eyepiece.

Monochromatic Aberrations: spherical aberration, coma, astigmatism, curvature of field, and distortion are the monochromatic aberrations. They were analyzed by Seidel in the 1850's.

Monochromatic Light - Light of a single wavelength.

Moondogs - reflections of the Moon, these are bright spots in the upper atmosphere (caused by ice crystals) that precede and follow the Moon in the sky.

MOT - Mirror On Top. ATM term for mirror grinding, where the mirror is on top of the grinding tool. See also TOT.

Mount - a mechanical device that supports the optical tube assembly of a telescope. There are many configurations, but only 2 basic types: alt/az and equatorial.

Multi-coated: the air to glass surfaces of lenses that are antireflection coated with more than one layer of coatings. In the past, this term was distinguished from "fully multi-coated," where "fully" meant every air-glass surface was so coated, while multi-coated could mean that some surfaces were left uncoated. This difference is no longer maintained; e.g., some manufacturers use "multi- coated" to refer to "fully multi-coated". Additionally, for some applications singly-coated optics are preferred. In general, a meaningless term, somewhat perpetuated by out of date information, occasional marketing hype, and sometimes misplaced brand loyalty. Today, nearly ALL high-quality eyepieces are multi-coated.

Mylar - an aluminized acetate film that is quite flexible. It is often used as a solar filter material for telescopes.

Myopia - near-sightedness. You can see near objects well, but not far ones.

N

Nadir - the opposite of zenith - the bottom-most point of the celestial sphere around you.

Nagler, Albert: foremost telescope ocular designer of the latter half of the 20th century, and beginning of the 21st century. He is best known for designs which offer large fields of view with good correction of off-axis astigmatism and chromatic aberration, in some cases out to 82 degrees of apparent field. Nagler's designs do not use any aspheric surfaces, which reduces manufacturing costs. While many opticians have designed multitudes of such oculars, most of them remain inventions on paper only; Al Nagler's company, TeleVue, manufactures many of Nagler's designs. He deserves fame, as his Ultrawidefield designs were the first commercially successful of the UWA designs.

Nagler Eyepiece - A highly-corrected, ultrawidefield eyepiece manufactured by TeleVue Optics.

Naked Eye - the eye used without optical aid (glasses excepted)

Narrowfield - an apparent field of view of 50 degrees or less. Most inexpensive eyepieces are narrowfields.

NEAF - Northeast Astronomy Forum & Telescope Show.

Nebula A cloud of dust and gas in space, usually illuminated by one or more stars. Nebulae represent the raw material the stars are made of.

Nebular Filters - These are restricted bandwidth filters that target specific frequencies of light, used to enhance views of dim targets such as nebulae.

Negative focal length: a lens or mirror which diverges light is said to have a negative focal length. If a collimated beam of light is passed through such an optic, it will diverge; if the angle of divergence is traced back through the optic to that angle's intersection, the negative of the distance between that point and the optic is its focal length. Common optical systems which have negative focal lengths include the Barlow lens and the secondary mirror on Cassegrain systems.

Negative Lens A lens that cannot form an image when used alone, but can be used together with positive lenses to correct their aberrations, to amplify an optical system, or to relocate an image.

Negative Lens Projection Photography - The photographic technique of using a telenegative amplifying lens to enlarge the image formed by a telescope and to project the image directly into the camera.

NELM - Naked Eye Limiting Magnitude. This refers to the magnitude of the faintest star that can be seen by the naked eye in a dark, moonless, sky.

Neutral Density Filters - Gray Filters used to reduce light from bright targets like the moon without introducing false color.

Neutron Star A compressed core of an exploded star made up almost entirely of neutrons. Neutron stars have a strong gravitational field and some emit pulses of energy along their axis. These are known as pulsars.

Newt - Newtonian Reflector

Newtonian Reflector - A telescope employing a paraboloidal primary and a smaller, flat diagonal mirror to form images: the first practical reflecting optical telescope, invented by Isaac Newton, consisting of a concave primary mirror and a flat secondary mirror that diverts light out the side of the tube. For best correction on-axis, the Newtonian is made with a paraboloidal primary mirror. Small Newtonians of around f/14 or longer can give acceptable performance with a spherical mirror. Spherical Newtonians with an aperture stop at the radius of curvature can be made coma-free. See also coma.

NGC New General Catalog of Non-Stellar Astronomical Objects. A catalog of all visible deep-sky objects known at the time (late 19th Century) it was complied. You can find a corrected list free for download at http://www.ngcic.org/

Noctilucent Clouds - high clouds composed of ice crystals; visible long after sunset and seemingly illuminated by the Sun.

Nova A star that flares up to several times its original brightness for some time before returning to its original state. Often a convulsive explosion of the atmosphere of a very old star.

<< Prev Table of Contents Next >>

ASTRONOMICAL BOOKS

Tell Friend  

(112 Items) 1 2 3 4 5 6 7 8  Next Gallery View Click here for List Display
Sort By: Price | New | Brand | Category | Name
Agena Astro Products - The Great Atlas of the Sky, Jubilee Edition
New
Agena Astro Products - The Great Atlas of the Sky, Jubilee Edition
Item No. 786-20000

Agena Astro Products BOOKS The Great Atlas of the Sky by P.Brych
 
Our Price: $239.00
Buy Agena Astro Products - The Great Atlas of the Sky, Jubilee Edition
 

Sun Observer's Guide, Firefly Books
New
Sun Observer's Guide, Firefly Books
Item No. 896-23211
Manuf. No. Firefly 978-1-55297-941-9

A practical reference for how and why to view our nearest star. This book can start you making worthwhile observations.
 
Our Price: $14.95
Buy Sun Observer's Guide, Firefly Books
 

The History of Astronomy, Firefly Books
New
The History of Astronomy, Firefly Books
Item No. 896-23210
Manuf. No. Firefly 978-1-55407-537-9

This extraordinary book traces humans' interaction with the endless wonders of the night sky.
 
Our Price: $29.95
Buy The History of Astronomy, Firefly Books
 

Stargazing with a Telescope, Firefly Books
New
Stargazing with a Telescope, Firefly Books
Item No. 896-23208
Manuf. No. Firefly 978-1-55407-577-5

Stargazing with a Telescope is a practical guide that demystifies the process of buying and using a telescope.
 
Our Price: $19.95
Buy Stargazing with a Telescope, Firefly Books
 

Stargazing with Binoculars, Firefly Books
New
Stargazing with Binoculars, Firefly Books
Item No. 896-23207
Manuf. No. Firefly 978-1-55407-368-9

A practical, concise beginner's guide to viewing the night sky through binoculars
 
Our Price: $19.95
Buy Stargazing with Binoculars, Firefly Books
 

300 Astronomical Objects: A Visual Reference to the Universe, Firefly Books
300 Astronomical Objects: A Visual Reference to the Universe, Firefly Books
Item No. 896-23206
Manuf. No. Firefly 978-1-55407-175-3

A handy and comprehensive reference to the 300 most interesting celestial objects. This book provides a tour through the galaxy.
 
Our Price: $29.95
Buy 300 Astronomical Objects: A Visual Reference to the Universe, Firefly Books
 

Moon Observer's Guide, Firefly Books
Moon Observer's Guide, Firefly Books
Item No. 896-23203
Manuf. No. Firefly 978-1-55297-888-7

Moon Observer's Guide offers practical guidance to amateur astronomers viewing Earth's only natural satellite.
 
Our Price: $14.95
Buy Moon Observer's Guide, Firefly Books
 

Night Sky Atlas: The Moon, Planets, Stars and Deep Sky Objects, Firefly Book
Night Sky Atlas: The Moon, Planets, Stars and Deep Sky Objects, Firefly Book
Item No. 896-10719
Manuf. No. Firefly 978-1-55407-026-8

This Firefly book is a very nice introduction to astronomy for beginners.
 
Our Price: $29.95
Buy Night Sky Atlas: The Moon, Planets, Stars and Deep Sky Objects, Firefly Book
 

Software Bisque TheSkyX Professional Edition for Mac
Free Shipping
Software Bisque TheSkyX Professional Edition for Mac
Item No. 773-55161
Manuf. No. Software Bisque SKYX_PRO_MAC

TheSkyX Professional Edition for Mac is the next major release in TheSky's 25+ year history
 
Our Price: $349.00
Buy Software Bisque TheSkyX Professional Edition for Mac
 

Software Bisque TheSkyX Professional Edition for Windows
Free Shipping
Software Bisque TheSkyX Professional Edition for Windows
Item No. 773-55160
Manuf. No. Software Bisque SKYX_PRO_WIN

TheSkyX Professional for Windows will get you charged up about your passion. Explore, engage, enjoy while getting the most from your observing sessions.
 
Our Price: $349.00
Buy Software Bisque TheSkyX Professional Edition for Windows
 

Sky & Telescope - Sky Atlas 2000.0 Companion, 2nd Edition
Sky & Telescope - Sky Atlas 2000.0 Companion, 2nd Edition
Item No. 846-10899
Manuf. No. Sky Publishing 46956

This essential reference features an alphabetical listing of every deep sky object plotted in Sky Atlas 2000.00.
 
Our Price: $29.95
Buy Sky & Telescope - Sky Atlas 2000.0 Companion, 2nd Edition
 

Sky & Telescope - SKY ATLAS 2000.0 DESK UNLAMINATED
Sky & Telescope - SKY ATLAS 2000.0 DESK UNLAMINATED
Item No. 846-10898
Manuf. No. Sky Publishing 46883

Includes close-up charts of such areas as the celestial poles and the Virgo-Coma galaxy region, as well as an acetate coordinate-grid overlay for determining accurate positions
 
Our Price: $34.95
Buy Sky & Telescope - SKY ATLAS 2000.0 DESK UNLAMINATED
 

Sky & Telescope - SKY ATLAS 2000.0 FIELD LAMINATED
Eligible for Rewards
Sky & Telescope - SKY ATLAS 2000.0 FIELD LAMINATED
Item No. 846-10895
Manuf. No. Sky Publishing 46921

The standard against which all other star atlases are measured, each version of Sky Atlas 2000.0 contains 26 charts covering the whole sky and showing 81,312 single, multiple, and variable stars of magnitude of 8.5 and brighter and 2,700 deep-sky objects
 
Our Price: $69.95
Buy Sky & Telescope - SKY ATLAS 2000.0 FIELD LAMINATED
 

Sky & Telescope: SKY ATLAS 2000.0 FIELD UNLAMINATED
Sky & Telescope: SKY ATLAS 2000.0 FIELD UNLAMINATED
Item No. 846-10890
Manuf. No. Sky Publishing 46891

Field Version: Stars and deep sky objects are white on a black background. Unbound and printed on heavy paper
 
Our Price: $34.95
Buy Sky & Telescope: SKY ATLAS 2000.0 FIELD UNLAMINATED
 

Sky & Telescope - Astronomy Library Sky Atlas 2000.0 Deluxe Edition
Eligible for Rewards
Sky & Telescope - Astronomy Library Sky Atlas 2000.0 Deluxe Edition
Item No. 846-10880
Manuf. No. Sky Publishing 46875

Sky Atlas 2000.0 Deluxe Edition contains 26 charts showing close to 85,000 objects (stars and deep sky objects) down to magnitude 8.5
 
Our Price: $69.95
Buy Sky & Telescope - Astronomy Library Sky Atlas 2000.0 Deluxe Edition
 

1 2 3 4 5 6 7 8  Next
 


Scope City 100% Satisfaction Guarantee

Scope City unconditionally guarantees that you will be 100% satisfied with your mail order purchase, or just
return the merchandise in original condition within 15 days for a Full Refund, less shipping and handling charges!