New metric can help quantify image quality of the Sun taken from ground-based telescopes

Source: The post is based on the article “New metric can help quantify image quality of the Sun taken from ground-based telescopes” published in PIB on 22nd May 2023

What is the News?

A new metric has been proposed by scientists that can help quantify the image quality of the Sun taken from ground-based telescopes.

What is the drawback currently with ground-based solar telescopes?

Dynamic events like flares, prominences and Coronal Mass Ejections take place on the surface of the Sun.

This has made the Sun the focus of interest of our astronomers. The Sun is also the closest star which means it can be studied in great detail and properties of other stars may be extrapolated by the understanding of the Sun. 

To resolve even the smallest features in greater detail, large telescopes are built.

However, there is a major disadvantage when the telescopes are on the ground. The light from the Sun passes through the Earth’s atmosphere, which is not a homogenous medium. 

There are random temperature fluctuations that lead to refractive index fluctuations. This causes the light to bend randomly and can be observed as the variation of intensity and position of the image on the detector. 

One way to overcome this is to use an adaptive optics (AO) system to measure and correct for the distortions introduced by the atmosphere in real-time.

But there is no way one can quantify the performance of the AO system or quantitatively evaluate the quality of images from ground-based telescopes.

What have scientists developed to overcome this drawback?

Scientists have proposed to use a novel metric called the root-mean-square (rms) granulation contrast to quantify the image quality of ground-based solar telescopes.