The plate scale of a

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

connects the

angular separation Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...

of an object with the linear separation of its image at the

focal plane In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the '' focal points'', the principal points, and the nodal points; there are two ...

. If focal length is measured in millimeters, the plate scale in radians per millimeter is given by angular separation , and the linear separation of the image at the focal plane , or by simply the focal length :

p =\frac =\frac\ ,

since

s =f \theta\ .

Plate scale is usually expressed in

arcseconds A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

per millimeter:

p \approx\frac,

where is in , or expressed in

per pixel after further division through the pixel scale.

Plate scale on JWST FGS/NIRISS

The pixel scale of the

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. As the largest telescope in space, it is equipped with high-resolution and high-sensitivity instruments, allowing it to view objects too old, Lis ...

component Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph is about 0.066 arcsec/pixel. It uses a pixel array with a pixel size of per side with a

field of view The field of view (FOV) is the angle, angular extent of the observable world that is visual perception, seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to elec ...

of https://jwst-docs.stsci.edu/jwst-near-infrared-imager-and-slitless-spectrograph#JWSTNearInfraredImagerandSlitlessSpectrograph-Opticalelements

Notes

Astrophotography Equations of astronomy {{telescope-stub

Plate scale on JWST FGS/NIRISS

See also

Notes