Angular Resolution / Beam Width

[yellowputty]

Hello all,

In terms of Radio Astronomy, can someone please explain to me the difference between the Beam Width and the Angular Resolution? I have a 1.2m dish to play about with, and I wanted to know what it could resolve. I thought I was sorted by using the diffraction formula, but then I read about Beam Width. I found a calculator online, and when the resolution formula gave me 1.45, the Beam Width was 1.44. It seems logical to me that the FWHM of the main lobe fairly accurately describes the resoltution of a Radio Scope.

If they are different, does the Beam Width differ, because it doesn't encorporate the entire beam, and the beam geometry can differ?

Sorry if that sounded confusing.

Thank you.

 

[AndyW]

Thank you for your question about the difference between Beam Width and Angular Resolution in Radio Astronomy. I am happy to explain these concepts to you.

The Beam Width and Angular Resolution are related, but they are not the same thing. The Beam Width refers to the width of the main lobe of the antenna pattern, which is the central part of the beam that is used for observations. This can be described by the Full Width at Half Maximum (FWHM) of the main lobe. The Angular Resolution, on the other hand, is a measure of the smallest angular separation between two objects that can be resolved by the telescope. It is usually expressed in units of arcseconds or degrees.

In simple terms, the Beam Width determines the size of the area that the telescope is observing at any given time, while the Angular Resolution determines the smallest details that can be resolved within that area. So even though the Beam Width may be small, if the Angular Resolution is not high enough, the telescope will not be able to distinguish between closely spaced objects within that beam.

In your example, the diffraction formula and the Beam Width calculator are giving you similar values because they are both taking into account the size of your 1.2m dish. However, the Beam Width may vary depending on the geometry and design of the antenna, while the Angular Resolution is a fixed value based on the size of the antenna and the wavelength of observation.

I hope this explanation helps clarify the difference between Beam Width and Angular Resolution in Radio Astronomy. If you have any further questions, please don't hesitate to ask. Happy observing!