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Astronomical observing techniques

Depending on the nature of celestial objects and what one wants to know about them, different techniques are applied to collect their emission.

Obviously, and most well-known, to obtain the distribution of light from a region of the sky, one will use the technique of imaging.

However, for studies of emission lines, another technique, namely spectroscopy, is much more well-suited.

To monitor the emission of a time-variable object, astronomers perform photometric observations.

In everyday we are not used to dealing with this effect, but a lot of cosmic radiation is polarised. The observing mode to register such polarised emission is polarimetry.

It is for many reasons necessary to know the precise positions of objects on the sky (not the least of which being that one wants to find them, possibly with a telescope with a very small field of view... The process of determining high-accuracy positions and thereby developing an extremely accurate coordinate reference frame is called astrometry.

For some applications the angular resolution of even the largest existing single telescopes is not sufficient, while it is (either economically or technically, or both) impossible to build yet larger ones. This led to the development of a "trick", using which astronomers can obtain higher-resolution data by replacing a larger single telescope by an array of several smaller ones, the so-called interferometry or aperture synthesis.

These techniques, including examples of actual observations, are described on dedicated pages:

New techniques, like observations with energy-sensitive cameras, now enable astronomers to combine several of the above techniques in a single observation data set. This is explained on a separate page about multi-dimensional observing data sets.

Another technique which is used to optimise the surface accuracy of radio telescopes is called radio holography.