RADIO TELESCOPE

My radio telescope has four antennae and hence four channels, as follows:

1. Solar Observation Channel, using a large satellite TV antenna, centre frequency 12 GHz - for observation of sunspot activity.

2. Milky Way Observation Channel, using a 1m parabolic mesh antenna, centre frequency 1.42 GHz - for observation of cool hydrogen clouds in the Milky Way galactic arms.

3. Meteor Detection Channel, using a folded dipole antenna modified with a parasitic back-reflector, centre frequency  50.408 MHz - for observation of meteor activity utilising the British Astronomical Association GB3MBA radio beacon.

4. Sudden Ionospheric Disturbance (SID) Channel, using an L-shaped antenna with an electrical length of 7 ft (horiz) x 14.3 ft (vert).

SOLAR OBSERVATION

The surface of the Sun that we observe in the visible is called the photosphere. But the lower region of the Sun's atmosphere is called the chromosphere and, together with the corona, is where most of its radio emissions arise. 

The thermal component of solar radiation follows the black body law and is predominant at high frequencies (Infrared, f> 300 GHz & also some high-end radio waves, f> 3 GHz), while the non-thermal component (synchrotron radiation) is predominant at lower frequencies (microwave, f <3 GHz).

Note: Infrared spectrum is 300 GHz to 400 THz. 

So, my telescope is picking up mainly synchrotron radiation, produced by charged particles being accelerated by the sun’s magnetic field.

An active Sun has much larger flux density than does a quiet Sun in the frequency range between 100 MHz (3-m wavelength) and 30 GHz (1 cm wavelength). So the telescope is ideal for picking up flare activity.

Synchrotron radiation occurs when a moving particle is accelerated in a direction perpendicular to its movement, i.e., outwards from the sun. 

NOTE: the condition for the production of an EM wave is acceleration of charged particles.

GALACTIC HYDROGEN OBSERVATION

The Milky Way contains an abundance of cool, 'molecular' hydrogen clouds (H2), whose molecules radiate electromagnetic radiation predominately in the microwave frequency band, the peak occurring at  1.420405752 GHz.

This signal is very weak and sits amidst the general 'noise', but my radio telescope is able to detect that peak by employing spectrum averaging software, which elevates the wanted signal sufficiently above the noise floor for detection. 

What is interesting is that the peak signal frequency of the hydrogen will vary depending upon whereabouts the telescope is aimed within the galaxy. This is due to the fact that different parts of the galaxy are moving at different relative velocities to us on Earth (due to the galactic rotation and other localised phenomena), and so this causes the radiated frequency to be modified by the Doppler Effect.

This radial velocity (velocity along the line of sight of the telescope) can actually be calculated by noting the observed frequency of the peak measured by the telescope and applying the formula below:

vR = -c{(fO-fE)/fO} 

...where fE = 1.420,405,752 GHz and fO = observed frequency and c is the speed of light. As it is a ratio, any unit of frequency can be used as long as it is consistent throughout the equation. Velocity is expressed in m/s if a value of c of 3 EXP 8 m/s is used.

Note: This equation starts with a minus sign to comply with the convention that a red shift, i.e. a receding velocity is a positive value, and a blue shift, i.e. an approaching velocity is a negative value.  

Using this technique, I can plot a radial velocity map of the observed parts of the Milky Way and, from any large velocity changes, distinguish between different galactic arms. 

The arms of the Milky Way are shown below: