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Star filter

Filter mounted at front of the camera lens gives videotaped light sources a starburst effect.
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A cross screen filter, also known as a star filter, creates a star pattern using a very fine diffraction grating embedded in the filter, or sometimes by the use of prisms in the filter. The number of stars varies by the construction of the filter, as does the number of points each star has.

A similar effect is achieved by photographing bright lights through a window screen with vertical and horizontal wires. The angles of the bars of the cross depend on the orientation of the screen relative to the camera.

In amateur astrophotography, a Bahtinov mask can be used to focus small astronomical telescopes accurately. Light from a bright point such as an isolated bright star reaching different quadrants of the primary mirror or lens is first passed through grilles at three different orientations. Half of the mask generates a narrow "X" shape from four diffraction spikes; the other half generates a straight line from two spikes. Changing the focus causes the shapes to move with respect to each other, as shown in the illustration. When the line passes exactly through the middle of the "X", the telescope is in focus and the mask can then be removed.

Key Terms

cross screen filter
definition
filter
fine diffraction
focus
half
mask
star filter
star pattern
usage

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Acronymn

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Synonymns

Star filter
Cross screen filter

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Sources & Credits

Last modified on September 29 2019
Content adapted from Wikipedia
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