Using a parabolic mirror in a reflecting telescope offers significant advantages, primarily in reducing spherical aberration. Spherical aberration occurs when light rays reflecting off the edges of a spherical mirror focus at a different point compared to those reflecting near the centre, leading to a blurred image. A parabolic mirror, however, has a shape such that all incoming parallel light rays (like those from distant stars) are reflected to a single focal point. This precise focusing enhances image clarity and sharpness, making it ideal for astronomical observation. Additionally, parabolic mirrors mitigate the need for corrective lenses, which can introduce chromatic aberration and additional light loss. This improvement in image quality is particularly beneficial for observing fine details in distant celestial objects, making parabolic mirrors a preferred choice in professional astronomical telescopes.

The aperture size of a telescope, which refers to the diameter of its primary light-gathering lens or mirror, significantly influences its observational capabilities. A larger aperture allows more light to enter the telescope, which is crucial for two main reasons. Firstly, it improves the telescope's light-gathering ability, making faint objects more visible and enhancing the overall brightness of the image. Secondly, a larger aperture increases the resolving power of the telescope, defined as its ability to distinguish between two close objects as separate entities. According to the Rayleigh criterion, the minimum angular resolution of a telescope is inversely proportional to the diameter of its aperture. Therefore, telescopes with larger apertures can resolve finer details and are more effective in studying distant celestial bodies like distant galaxies, nebulae, and star clusters.

Reflecting telescopes are often preferred over refracting telescopes for several reasons, especially in professional astronomical observations. One key advantage is that reflectors do not suffer from chromatic aberration, a problem inherent in refractors where different wavelengths of light do not converge at the same point, creating colour fringes around the image. This is because mirrors reflect all wavelengths equally, whereas lenses refract them differently. Additionally, reflecting telescopes can be built with much larger apertures since mirrors can be supported from behind, unlike lenses which can only be supported at their edges, limiting their size due to weight and structural issues. Larger apertures allow for greater light-gathering and resolving power. Moreover, mirrors are generally cheaper and easier to manufacture and maintain than large, high-quality lenses, making reflecting telescopes more cost-effective for large-scale astronomical research.

The eyepiece in a telescope plays a crucial role in magnifying the image formed by the objective lens or primary mirror. It is the final lens through which the observer views the image. The eyepiece's focal length is a key factor in determining the overall magnification of the telescope, as the telescope's magnifying power is calculated by dividing the focal length of the objective lens by that of the eyepiece. Changing the eyepiece with a different focal length can significantly alter the magnification. For instance, a shorter focal length eyepiece increases the magnification, allowing for closer views of celestial objects, which is particularly useful for detailed observations of planets and lunar features. However, higher magnification also reduces the field of view and can diminish image brightness and sharpness, especially in telescopes with smaller apertures. Therefore, selecting the appropriate eyepiece is essential for optimising the balance between magnification, field of view, and image quality based on the specific observational needs.

Atmospheric turbulence, often referred to as "seeing" in astronomy, significantly impacts the quality of astronomical observations through telescopes. This turbulence is caused by the movement of air and varying temperature layers in the Earth's atmosphere, which can distort the path of light as it travels from space to the surface. This distortion leads to a blurring and twinkling effect on the images of stars and other celestial objects, reducing the clarity and sharpness of the observations. The effects of atmospheric turbulence are more pronounced at higher magnifications and for telescopes with larger apertures, as they collect light from a larger area of the atmosphere. To mitigate these effects, astronomers often use adaptive optics, which involves real-time adjustments to the telescope's mirror or lens shape to compensate for atmospheric distortions. Additionally, selecting observation sites with stable atmospheric conditions, such as high-altitude locations or areas with minimal atmospheric turbulence, can also improve observation quality.