British Astronomical Association - Radio Astronomy Group

Radio Spectrum

Most amateur astronomers observe in Visible light. The electromagnetic spectrum encompasses a vast scope, starting almost at Direct Current and with frequencies up to 2.4×10²³ Hz (Gamma rays).

(image courtesy wikipedia)

As can be seen from the figure, visible light comprises a tiny fraction of the entire EM spectrum - everything else is considered to be fair game for radio astronomers

However, not all this radiation can actually penetrate the atmosphere. Additionally, much of the spectrum is used by commercial bodies - for example, television, mobile phones, data communications etc. In fact, there is actually very little left that is potentially usable yet unused. Because of this, certain bands of frequencies are protected and these should be considered if serious observations are planned. It is not necessary to stick to these bands though, in fact it can be much more rewarding and easier making use of existing consumer hardware and living with the interference. This is potentially no worse than that most optical astronomers have to put up with - observing through a light polluted sky.

Radio Astronomy Protected Frequencies

There are a number of internationally protected frequencies that are sererved for the use of Radio Astronomers. However, not all these are globally honoured. For example, the band 73 - 74.6MHz is peculiar to the USA and Canada whereas it is unrecognised in the UK. It should also be noted that the 608 - 614MHz band will lose its protection in the UK from September 2012.

Frequency band	Status	Radio astronomy use
13.36 - 13.41 MHz
25.55 - 25.67 MHz
37.5 - 38.25 MHz		Continuum observations
73 - 74.6 MHz		Solar wind observations. Continuum observations.
80.5 - 82.5 MHz		Pulsar observations
150.05 - 153 MHz		Continuum observations. Pulsar observations. Solar observations.
322 - 328.6 MHz		Continuum observations. VLBI
406.1 - 410 MHz		Continuum observations. Pulsar observations.
608 - 614 MHz		Continuum observations. VLBI
1400 - 1427 MHz		Spectral line observations 21cm hydrogen line
1660 - 1660.5 MHz		VLBI
1660.5 - 1668.4 MHz		VLBI Line observations. Continuum observations.
1668.4 - 1670 MHz
1718.8 - 1722.2 MHz
2655 - 2690 MHz		Continuum observations
2690 - 2700 MHz
3260 - 3267 MHz
3332 - 3339 MHz
3345.8 - 3352.5 MHz
4800 - 4990 MHz		Continuum observations
4990 - 5000 MHz		Continuum observations. VLBI
5000 - 5030 MHz		VLBI
6650 - 6675.2 MHz
10.6 - 10.68 GHz		Continuum meausurements. VLBI
10.68 - 10.7 GHz		Continuum observations. VLBI
14.47 - 14.5 GHz		Spectral line observations. VLBI
15.2 - 15.35 GHz		VLBI
15.35 - 15.4 GHz		Continuum observations. VLBI
22.01 - 22.21 GHz		Spectral line observations Water line
22.21 - 22.5 GHz		Spectral line observations Water line.
22.91 - 22.86 GHz		Spectral line observations Methyl Formate Ammonia
23.07 - 23.12 GHz		Spectral line observations
23.6 - 24.0 GHz		Spectral line observations Continuum observations Ammonia line
31.2 - 31.3 GHz		Continuum observations
31.3 - 31.5 GHz		Continuum observations
31.5 - 31.8 GHz		Continuum observations
36.43 - 36.5 GHz		Spectral line observations Hydrogen cyanide Hydroxil
42.5 - 43.5 GHz		Spectral line observations Silicon monoxide and many other lines
48.94 - 49.04 GHz		Spectral line observations Carbon monosulphide
51.4 - 54.25 GHz
58.2 - 59 GHz
72.77 - 72.91 GHz		Spectral line observations Formaldehyde line.
86 - 92 GHz		Spectral line observations. Continuum obserations
92 - 94 GHz		Spectral line observations. Diazenylium and many other lines.
95 - 100 GHz		Spectral line observations. Continuum observations.

The majority of Amateur Radio Astronomy observations are usually performed at less than 12GHz. Higher frequencies are deemed to be very exotic requiring very specialist construction and measurement techniques

Resources

Committee on Radio Astronomy Frequencies