<p>The following table is based on <a href="https://ieeexplore.ieee.org/document/1140521" rel="nofollow noreferrer">The measurement of large antennas with cosmic radio sources</a> (sorry for the paywall), Table I &quot;Radio Sources for Antenna Measurements&quot;, Panel A &quot;Flux Density and Polarization Data&quot;.  This table contains some of the brightest &quot;point sources&quot; at microwave frequencies.  I have extracted only the flux densities at 1 GHz to match the requested frequency range in the question.  Flux densities below 1 GHz will be different.</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>Source</th>
<th>Flux Density (fu)</th>
</tr>
</thead>
<tbody>
<tr>
<td>Cassiopeia A (Cas A, 3C461)</td>
<td>3185 <span class="math-container">$\pm$</span> 30</td>
</tr>
<tr>
<td>Cygnus A (Cyg A, 3C405)</td>
<td>2270</td>
</tr>
<tr>
<td>Taurus A (Tau A, 3C144)</td>
<td>986 <span class="math-container">$\pm$</span> 12</td>
</tr>
<tr>
<td>Virgo A (Vir A, 3C274)</td>
<td>285 <span class="math-container">$\pm$</span> 5</td>
</tr>
<tr>
<td>Orion A (Ori A, 3C145)</td>
<td>330</td>
</tr>
<tr>
<td>Hydra A (3C218)</td>
<td>60</td>
</tr>
<tr>
<td>Hercules A (3C348)</td>
<td>62</td>
</tr>
<tr>
<td>3C353</td>
<td>73</td>
</tr>
<tr>
<td>DR21</td>
<td>4</td>
</tr>
</tbody>
</table>
</div>
<p>1 fu = 10<sup>-26</sup> Wm<sup>-2</sup> Hz<sup>-1</sup> = 1 Jy</p>
<p>Locations are epoch 1950.0.</p>
<p>For a home system these are still likely to be very small signals.  Using the sun as a reference source may be a better choice even though it is &quot;extended&quot; and the location changes rapidly.  Whether you consider it extended or not of course depends on your angular resolution.</p>

CC BY-SA 4.0
2022-01-10T17:14:37.480Z
This is a good answer, although 1GHz isn't clear of terrestrial transmitters. I'll give it a try and see what happens. Thanks!
Craeft
CC BY-SA 4.0
2022-01-10T17:39:35.230Z
@Craeft If you can go somewhat higher in frequency above 1 GHz there are some protected bands.  I'm not as familiar with lower in frequency.
GrapefruitIsAwesome
CC BY-SA 4.0
2022-01-09T15:44:10.457Z
2022-01-09T15:44:10.457Z
GrapefruitIsAwesome
<p>I have a small antenna and radio system that can receive frequencies between 1MHz and 1GHz.  The system has a discone antenna. I plan to do some aperture synthesis based on the daily rotation of the Earth that will allow me to resolve a lune with a width of about one degree.</p>
<p>What objects and specific frequencies should I observe to test to see if the system and algorithm is functioning properly?</p>

CC BY-SA 4.0
2021-03-11T23:48:08.567Z
Interesting question! By aperture synthesis I think you mean a single antenna's received signal is recorded at several different times as it moves to different locations, and those are combined computationally off-line in a way similar to having multiple antennas at those locations. This works well for radar where phase and coherence of the source is controlled. Can aperture synthesis be used for single antenna receive-only radio astronomy systems? Are there any known examples of this being done with a single antenna?
uhoh
CC BY-SA 4.0
2021-03-11T23:59:12.503Z
I can do the aperture synthesis only because the antenna is a on the rotating Earth.  Like you said, as the Earth rotates, it's as if I have lots of antennas.  One limitation is that objects that move faster or slower than the "fixed stars" will look like noise to the synthesis algorithm.  I might be able to use different processing techniques to see the faster/slower objects.  I don't know of any examples of this being done like this, but I am not really in a position to know that sort of thing.  Part of the reason for posting was to see if anyone recognized what I was doing.
Craeft
CC BY-SA 4.0
2021-03-12T00:05:44.117Z
Okay got it, thanks! Your question about convenient calibration targets is a good one by itself and doesn't necessarily depend on the details of the analysis. You're looking for something that's strong and compact I'd guess.
uhoh
CC BY-SA 4.0
2021-03-12T00:15:13.350Z
Yes, and also within my receiver bandwidth, and likely to avoid Earth based transmitters.
Craeft
CC BY-SA 4.0
2021-03-12T18:24:26.193Z
In  1960s Cassiopeia A, Crab Nebula used to calibrate radiotelescopes.
A. Rumlin
CC BY-SA 4.0
2021-03-15T01:36:16.610Z
Now that your question has been here for two days I can add a bounty to it. I think it's a great question and am interested in its answer.
uhoh
CC BY-SA 4.0
2021-04-29T20:38:44.457Z
@A.Rumlin Could you please elaborate a bit on why Cassiopeia A has been used as reference source (and for what frequencies)?
B--rian
CC BY-SA 4.0
2021-05-01T01:00:14.653Z
@B--rian "the brightest extrasolar radio source in the sky at frequencies above 1 GHz" https://en.wikipedia.org/wiki/Cassiopeia_A
A. Rumlin
<radio-telescope><radio-astronomy>
Recommend a radio calibration target for amateur radio telescope
Craeft
# Recommend a radio calibration target for amateur radio telescope

(Asked by: username_0 on 2021-03-11)

I have a small antenna and radio system that can receive frequencies between 1MHz and 1GHz. The system has a discone antenna. I plan to do some aperture synthesis based on the daily rotation of the Earth that will allow me to resolve a lune with a width of about one degree.

What objects and specific frequencies should I observe to test to see if the system and algorithm is functioning properly?

**Tags:** radio-telescope, radio-astronomy

> **Comments:**
> **username_1**: Interesting question! By aperture synthesis I think you mean a single antenna's received signal is recorded at several different times as it moves to different locations, and those are combined computationally off-line in a way similar to having multiple antennas at those locations. This works well for radar where phase and coherence of the source is controlled. Can aperture synthesis be used for single antenna receive-only radio astronomy systems? Are there any known examples of this being done with a single antenna?  
> **username_0**: I can do the aperture synthesis only because the antenna is a on the rotating Earth.  Like you said, as the Earth rotates, it's as if I have lots of antennas.  One limitation is that objects that move faster or slower than the "fixed stars" will look like noise to the synthesis algorithm.  I might be able to use different processing techniques to see the faster/slower objects.  I don't know of any examples of this being done like this, but I am not really in a position to know that sort of thing.  Part of the reason for posting was to see if anyone recognized what I was doing.  
> **username_1**: Okay got it, thanks! Your question about convenient calibration targets is a good one by itself and doesn't necessarily depend on the details of the analysis. You're looking for something that's strong and compact I'd guess.  
> **username_0**: Yes, and also within my receiver bandwidth, and likely to avoid Earth based transmitters.  
> **username_2**: In  1960s Cassiopeia A, Crab Nebula used to calibrate radiotelescopes.  
> **username_1**: Now that your question has been here for two days I can add a bounty to it. I think it's a great question and am interested in its answer.  
> **username_3**: @A.username_2 Could you please elaborate a bit on why Cassiopeia A has been used as reference source (and for what frequencies)?  
> **username_2**: @username_3 "the brightest extrasolar radio source in the sky at frequencies above 1 GHz" https://en.wikipedia.org/wiki/Cassiopeia_A  

---

## 1 answers

### Answer by username_4 on 2022-01-09. Score: 4 | Accepted answer

The following table is based on [The measurement of large antennas with cosmic radio sources](https://ieeexplore.ieee.org/document/1140521) (sorry for the paywall), Table I "Radio Sources for Antenna Measurements", Panel A "Flux Density and Polarization Data". This table contains some of the brightest "point sources" at microwave frequencies. I have extracted only the flux densities at 1 GHz to match the requested frequency range in the question. Flux densities below 1 GHz will be different.

| Source | Flux Density (fu) |
| --- | --- |
| Cassiopeia A (Cas A, 3C461) | 3185 $\pm$ 30 |
| Cygnus A (Cyg A, 3C405) | 2270 |
| Taurus A (Tau A, 3C144) | 986 $\pm$ 12 |
| Virgo A (Vir A, 3C274) | 285 $\pm$ 5 |
| Orion A (Ori A, 3C145) | 330 |
| Hydra A (3C218) | 60 |
| Hercules A (3C348) | 62 |
| 3C353 | 73 |
| DR21 | 4 |

1 fu = 10-26 Wm-2 Hz-1 = 1 Jy

Locations are epoch 1950.0.

For a home system these are still likely to be very small signals. Using the sun as a reference source may be a better choice even though it is "extended" and the location changes rapidly. Whether you consider it extended or not of course depends on your angular resolution.

> **Comments:**
> **username_0**: This is a good answer, although 1GHz isn't clear of terrestrial transmitters. I'll give it a try and see what happens. Thanks!  
> **username_4**: @username_0 If you can go somewhat higher in frequency above 1 GHz there are some protected bands.  I'm not as familiar with lower in frequency.  

---

