Obs Astro OPTICS Part 4

Created by: JProx01
Created on: 23-06-22 22:31

Defocus

the longitudinal displacement of the effective focal plane from the first order or Gaussian focal point. This causes a radial expansion of the image point on the effective image plane, decreasing the luminance of each point and causing point images to ove

1 of 11

Decenter

the displacement of an optical element so that its center is no longer on the optical axis

2 of 11

Tilt

the rotation of an optical element around an axis that passes through the center of the element and is perpendicular to the optical axis

3 of 11

Collimation

the process of adjustment that eliminates tilt and decenter from the optical system

4 of 11

Spherical aberration

a failure of focus, caused when rays parallel to the optical axis have different focal lengths at different aperture heights s. It produces a roughly uniform, concentric defocus around all the bright elements in all parts of an image, and a blurring in ex

5 of 11

Coma

a failure to magnify equally off axis light rays passing through the objective or eyepiece. Unlike spherical aberration, the effect is not constant within the same concentric aperture height height (s); instead the magnification also varies with field hei

6 of 11

Distortion

is caused by a failure to magnify the image equally as the field height increases. It is characterized in two ways. In positive or rectilinear distortion and In negative or angular magnification distortion

7 of 11

positive distortion / rectilinear distortion

the magnification increases toward the edge of the field: this causes straight lines to appear curved outward, even when the image is stationary

8 of 11

negative distortion / angular magnification distortion

the magnification decreases toward the edge of the field: this causes straight lines to appear projected onto a spherical surface curved toward the viewer, which is especially noticeable when the optical axis is moved — the image then appears to "roll awa

9 of 11

Field curvature / Petzval curvature

a failure to focus the entire image on a single plane perpendicular to the optical axis. Instead the focal "plane" is a paraboloid surface resembling a bowl or meniscus. This produces a characteristic inability to focus the center and edges of the field a

10 of 11

Astigmatism

when light rays from perpendicular cross sections of the image cone do not have the same focal distance along the optical axis. It is therefore an error both of focus and of magnification.

11 of 11

Other cards in this set

Card 2

Front

the displacement of an optical element so that its center is no longer on the optical axis

Back

Decenter

Card 3

Front

the rotation of an optical element around an axis that passes through the center of the element and is perpendicular to the optical axis

Back

Card 4

Front

the process of adjustment that eliminates tilt and decenter from the optical system

Back

Card 5

Front

Back

View more cards

Get Revising

Obs Astro OPTICS Part 4