Astrophysics (Index)About

filter

(optical filter)
(optical device to filter out part of the EMR spectrum)

In astronomy, optical filters are used with telescopes to limit the spectrum reaching a sensor, by which an image over a more-limited range of electromagnetic radiation can be produced. A sharp cutoff at some precise wavelength is typically unachievable, so their sensitivity function generally shows a hill-like (or somewhat bell-curve-like) peak. They are used for visible light and adjacent regions of the electromagnetic spectrum (within the infrared and ultraviolet bands).

The term passband can be thought of as the specification of such a filter, but the two terms are often treated almost as synonyms, and often the letter identifying the band is used to refer to the filter or to the intensity of an object (such as a star) seen through the filter. The definition and standardization of passbands (photometric systems) similarly applies to filters for those passbands.

There are also filters for higher energy EMR, e.g., X-rays.


(telescopes,equipment)
Further reading:
https://en.wikipedia.org/wiki/Astronomical_filter
https://en.wikipedia.org/wiki/Optical_filter
http://astronomy.swin.edu.au/cosmos/F/Filters
https://mcdonaldobservatory.org/research/instruments/ubvri-filters
http://spiff.rit.edu/classes/phys440/lectures/filters/filters.html
https://www.opticalmechanics.com/telescope-filter/

Referenced by pages:
absolute magnitude (M)
aperture photometry
apparent magnitude (m)
Atlas 3D
B
back end instrument
bandpass filter
bandwidth
BATC
Big Bear Solar Observatory (BBSO)
color index
Dartmouth Stellar Evolution Database (DSED)
DKIST
exoplanet eclipse light curve
filter designator
first galaxies
front end instrument
G band (G)
H-alpha (Ha)
H-beta (Hβ)
HEAO-2
Holmberg radius (RH)
I band
IPHAS
JHK photometric system (JHK)
K band
K correction
light pollution
linearly variable filter (LVF)
luminosity (L)
Lyman-break galaxy (LBG)
MKO photometric system
NIRCam
NIRSpec
Pan-STARRS
particle spectrometer
passband
photometer
photometric redshift (photo-z)
photometric system
photometry
plate
R band
rare designator prefixes
sensitivity function (S)
sky subtraction
SkyMapper Southern Survey (SMSS)
Sloan 2.5m Telescope
spectral band
spectral flux density (S)
SPHEREx
Strömgren photometric system
SUNRISE
SuperCOSMOS Sky Survey (SSS)
synthetic photometry
U
ugriz photometric system
UK Schmidt Survey
USNO Twin Astrograph
UVCANDELS
V
Voyager
Wesenheit function
WFC3

Index