Some Observations

1420MHz Hydrogen Line Emissions

A few examples of  H line signals,  Doppler & velocity profiles, extended Right Ascension repeated spectrum measurements and signal intensity distribution plots,

h Line

An example of a complex H Line spectrum showing various source components with different Doppler shifts / velocities


h line 2

Repeated 1MHz wide frequency scans of H Lines as a function of Time (Right Ascension) [This method captures the peak level of any H Line signal irrespective of its exact frequency / Doppler shift]



A map of the H Line intensity in the region around the Cygnus Arm of the Milky Way



1453.5MHz Measurements

The measurements shown below are made at a frequency close to the 1420MHz H Line frequency  [1453.5MHz in this case] . Received power is predominantly from synchrotron emissions – not from Hydrogen ground state  spin transitions - and shows a  less intense distribution than at the H Line frequencies.


Map of signal intensity @ 1453.5MHz (away from H Lines) along Galactic Plane



1453.5MHz signal intensity registered to optical image of Galactic Plane



409MHz Measurements

The map shown below is generated from measurements at 409MHz using the 3m Dish and a Mk 2 Quagi feed.     
The –3dB BW is about 170  as shown in the overlay on the map.

408 map

409MHz Intensity Map -10 to +60Dec & 17 to 22hrs R.A.

mk2 feed

Mk2 408 Feed

408 dish

The 3m dish and 408MHz Mk2 Feed used for Measurements



Observation of Cygnus A & Galactic Plane @ ~3.9GHz


This observation was made using the 3m Dish and the C Band Feed.

The signal intensity from Cygnus A and the Galactic Plane is much lower at these frequencies than at UHF or VHF. The graph above shows the signal level as a function of time / RA (reversed) plotted on top of a 408MHz radio map of this region of sky from ‘Radio Eyes’ software. The original measurements are due to Haslam et al. At almost 4GHz the meteorological conditions prevailing during the measurement affects the stability of the observation. Rain in particular will disturb the measurement.


Cygnus A & Galactic Plane (RA Reversed) - Radio Eyes Picture


Cygnus A Radio emission @ 21cm (Galaxy is at the centre)



Observations of The Moon


Click image for larger version



406MHz Interferometer Measurements

The measurements shown below are made using a 406MHz interferometer constructed from two Twin Quagi antennas mounted on towers separated by 30m. The output from this system is a fringe pattern with a period determined by the observing frequency, the baseline and the source Declination.

Measurements are made with the antennas pointing due South at an  appropriate Declination for the source to transit the beam. At the present time ( Feb 08) the system measures the Total Power as well as the fringe signal from the point sources. Thus the gentle ‘bump’ in the graph on the left of the page shows the amplitude of the signal from the outer rim of the Galactic Plane. Hopefully this year I will build the electronics to turn this system into a Phase Switched Interferometer that will ignore the background signal from diffuse sources and produce only fringes for the point source of interest.  This current interferometer has an angular resolution in the E-W plane of ~1.50 degrees.


Total Power Plot showing signals from Galactic Plane & Taurus A



Processed data showing only the Fringe Pattern from the point source TaurusA



Optical Photograph of the Radio Source Taurus A - NGC1952 3C144 CTA36 M1 [Crab Nebula] SNR 6,300Ly


This supernova remnant lies in the constellation of Taurus and can be found above the well known ‘Orion – The Hunter’ in the northern hemisphere.

Right Ascension: 05:34:30
Declination: 22:00:57

Freq: 178 MHz     Flux: 1420 Janskys
Freq: 960 MHz     Flux: 1030 Janskys
Calculated Spectral Index: 0.19

Cassiopeia A is a another supernova remnant [SNR]  often observed by amateur radio astronomers and is much brighter than Taurus A

Cygnus A is another bright ‘point source’ and it is not a supernova remnant in the Milky Way. It is a remote Galaxy undergoing violent change producing an immense radio (and other electromagnetic) output


Virgo A

Another extra galactic radio source is Virgo A. This is a giant elliptical galaxy in the constellation of Virgo. It too is a highly active and unusual galaxy producing jets of highly relativistic particles over very large distances that radiate at many wavelengths by the synchrotron process involving weak large scale magnetic fields. Al though it is not as strong a source as the others previously mentioned it can be observed by amateurs. Below is an example observation of this source.


This is the Total Power basic plot of signal strength for a transit of Virgo A [Note the rising curve as the beam starts to track into the inner part of the Galactic Plane]


Processed Data showing only the Fringe Pattern due to the 'Point Source' Virgo A [as Virgo is a point source in a 'cold' region of sky it can be used to calibrate system sensitivity]

Virgo A  3C274   M87    Right ascension 12:30:48  Declination 12:22:59  Freq: 408 MHz Flux: ~560 Janskys Calculated Spectral Index: 0.79
It gives a great deal of satisfaction to develop stable equipment that is capable of detecting and recording signal from galaxies such as Virgo A . It is amazing to realise that amateur efforts can be rewarded by a feeling of almost personal contact with something as large, remote and immensely powerful as a radio galaxy like Virgo A. It is through the efforts of technology that people can experience this ‘contact’.


A composite picture showing an Optical Image of M87 Virgo A with its relativistic Plasma Jet (click image to enlarge).

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