Hartmann mask
Encyclopedia
Hartmann mask is a tool to help focus
ing telescope
s, mainly used by amateur astronomers.
or lens
produces the same image as the whole optical element. The light
is focused in the focal point. The light rays, however, go through different points of a plane before or behind the focus.
This phenomenon can be used when focusing a telescope. The Hartmann mask is a simple opaque mask containing two or three holes. (This device is called a Hartmann mask if it has multiple holes, or a Scheiner disk if it has two holes.) The mask covers the aperture of the telescope.
When the apparatus is out of focus, multiple images can be seen if the telescope is pointed towards a bright light source (Moon, bright star - important: a telescope should NEVER be pointed at the Sun without a proper filter
! Ignoring this warning may cause irreparable damage to the equipment and the observer's eyesight). Adjusting the focuser, the images can be made to overlap, forming a single bright, clear picture.
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
ing 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...
s, mainly used by amateur astronomers.
Theory and practice
Every part of a mirrorMirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
or lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
produces the same image as the whole optical element. The light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
is focused in the focal point. The light rays, however, go through different points of a plane before or behind the focus.
This phenomenon can be used when focusing a telescope. The Hartmann mask is a simple opaque mask containing two or three holes. (This device is called a Hartmann mask if it has multiple holes, or a Scheiner disk if it has two holes.) The mask covers the aperture of the telescope.
When the apparatus is out of focus, multiple images can be seen if the telescope is pointed towards a bright light source (Moon, bright star - important: a telescope should NEVER be pointed at the Sun without a proper filter
Filter (optics)
Optical filters are devices which selectively transmit light of different wavelengths, usually implemented as plane glass or plastic devices in the optical path which are either dyed in the mass or have interference coatings....
! Ignoring this warning may cause irreparable damage to the equipment and the observer's eyesight). Adjusting the focuser, the images can be made to overlap, forming a single bright, clear picture.