lp/mm
Line Pairs per Millimetre (lp/mm) - Units used to measure image intensifier resolution. Usually determined from a 1951 Air Force Resolving Power test target. The target is a series of different sized patterns composed of three horizontal and three vertical lines. The lines and spacing between lines in each of the different patterns differ in width; the narrower the width, the greater the resolution is needed to distinguish the lines in a given pattern. Human test subjects must be able to clearly distinguish all the horizontal and vertical lines of a particular pattern in order for an image intensifier to achieve the resolution represented by that pattern.

acrmin
Un minuto de arco o arcmin es una unidad del ángulo plano frecuentemente utilizada en artillería y en astronomía, equivalente a 1/60 de un grado. Un grado se define como 1/360 de un círculo, de manera que un arcmin es 1/21600 del arco de un círculo o (π/10800) radianes. Generalmente se utiliza el sufijo prima (′) (U+2032, ′); Un arcominuto se escribe 1′ (o también 1').   Unidades angulares:grado-arcmin-arcsec-radián

What is a degree?

      This measure is based on the fact that a circle is composed of 360 degrees. From the perspective of an observer on Earth the sky above us is a sphere with a circumference of 360 degrees. At any one time 180 degrees of sky are visible above your horizon. Such high numbers are usually only used to measure the tails of bright, naked-eye comets.
      The moon and the sun make nice measuring sticks as each is very close to one-half degree in diameter. Among deep-sky objects, the Andromeda Galaxy is about 2.5 degrees long.

What is an arcmin?

      This measure technically represents 1/60 of a degree. For comets it is typically used to measure the diameter of the coma and the length of comet tails.
      When at its brightest, Jupiter usually displays a diameter near 0.8 arcmin. Among popular deep sky objects, the Ring Nebula (M57) has a diameter of just over 1 arcmin and the Dumb-bell nebula in Vulpecula is about 8 arcmin long and 5 arcmin wide.

What is an arcsec?

      Technically it is 1/3600 of a degree and 1/60 of an arcmin. It is typically used to measure the diameter of the nuclear condensation within a comet, as well as the coma and tail of very distant comets.
      Planets represent other astronomical objects whose diameters are given in arcsec. As noted under arcmin, Jupiter usually attains a diameter of 45 to 50 arcsec when closest to Earth. On the smaller side, Uranus typically reaches a diameter of 3 arcsec each year, while Neptune is normally around 2 arcsec.


ASPECT RATIO
  • The relationship between the width and the height of an image. To avoid distortion this ratio must be kept constant when displaying an image on different screens.
    www.scottygroup.com/glossary
  • Refers to the relationship between the width and height of a television screen. A standard television has an aspect ratio of 4:3 while a widescreen television has an aspect ratio of 16:9.
    www.flat-screen-tv.info/digital-television-glossary-1.htm
  • The ratio of a television picture width to height. In NTSC video, the standard is 4:3. In HDTV and SDTV widescreen video, it is 16:9.
    www.wgcu.org/watch/hdtv_glossaryofterms.html
  • Proportion of picture width to height such as 1.37:1 or 1.85:1, or 2.35:1.
    www.kodak.com/US/en/motion/students/handbook/glossary.jhtml

    • http://www.thedigitalbits.com/articles/anamorphic/aspectratios/widescreenorama.html