It is possible to build "radio images" of the studied area of the sky creating false color maps showing the spatial distribution of the intensity (or other property) of the received signal.
A single antenna radio telescope is the analogue of a lens or a mirror with a photocell mounted on the focal point: to produce a map of the radio-sky brightness is necessary to observe the region, point by point.

 

map radio-brightness

 


The easiest way:

  1. Point the antenna of the radio telescope on the meridian of interest declination.

  2. Wait for the rotation of the Earth allowing for the registration of the received signal at each "swiping" of sky intercepted by the beam of the antenna.

Changing after each scan the declination and repeating the registration process, you can complete the sky mapping, stripe for stripe.

 

The following requirements are important:

  • The scenery observed must have radiation characteristics stationary in time. Since the map is constructed at different times, making numerous and repeated scans of the sky in different forms, the radiation characteristics of the scenario should not change over time.

  • The receiving system must be a measuring instrument stable and repeatable, to avoid introducing errors due to drift and / or fluctuations in the level of the reference scale.

  • The radio-environmental interference must be "tolerable" for long periods of time. In "difficult" cases it is always possible to repeat in better times the size of the "strip" of sky considered as unsatisfactory. Long time.

The procedure of observation, best in amateur level for a survey of the sky, consists to point the antenna on the meridian declination desired and allow the rotation of the earth to perform a scan of a "strip" of the sky in this declination.

Each scan ("strip") is specific to a given declination.

This is a very slow method, but allows considerable flexibility in the control of the quality of every single scan (interference), with the possibility of identifying the scans which must be repeated.

Each scan will be characterized by its own baseline, according to the amount of radiation from the ground picked up by the antenna (oriented to the specific declination): the final composition of the map will have to take into account of this situation with appropriate compensation in the process of data reduction.

 

radio map of the sky at 30 MHz frequency

 

radio map of the sky at 408 MHz frequency

 

Further details can be found at the Downloads section.