CH 05

Optimal exposure for faint objects

The diameter of the telescope and the length of the exposure are important to make a very dim object appear brighter.

Radio telescopes vs Optical telescopes

Radio telescopes can observe objects in the daytime and even when it's cloudy, unlike optical telescopes.

Hubble Space Telescope resolution

The angular resolution of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light.

Telescope observations on Mauna Kea

The large research observations on Mauna Kea use giant reflecting telescopes.

Spectrographs purpose

Spectrographs separate the various colors of light, allowing astronomers to determine stellar composition.

Interferometry

The twin 10-m Keck telescopes can work together through interferometry to obtain better angular resolution.

Chandra X-ray observatory feature

The Chandra X-ray observatory focuses X-rays with grazing incidence mirrors.

Light-collecting area comparison

A 10-meter telescope has a larger light-collecting area than a 4-meter telescope.

Galileo's telescope type

Galileo's designs using lenses were examples of refracting telescopes.

Need for large telescopes

At certain wavelengths, telescopes with vast light-collecting areas are necessary to map faint cosmic signals.

Radio astronomers arrays

Arrays of multiple telescopes can produce maps of radio emission as detailed as optical images, known as interferometers.

X-ray image requirements

A telescope designed to be launched into space is needed for successful X-ray imaging of high-energy sources.

Penetrating dust and smog

X-ray radiation is more able to penetrate dust and smog than visible light.

Light deflection by lenses

The thickest lenses deflect and bend light the least.

Professional research telescopes

Most professional research telescopes are reflectors because large mirrors are easier to build than large lenses.

Largest light-gathering power

A circle with a diameter of 1 m has the most light-gathering power.

Resolution image sharpness

The image is sharpest when the ratio of wavelength to telescope size is close to unity.

Lag time of light

As objects get farther away, the 'lag time' for light becomes more significant.

Reasons for larger telescopes

Larger telescopes collect more light and produce less scattering, improving angular resolution.

High observatory locations

Professional observatories are built on high mountaintops to reduce atmospheric blurring.

Optical vs Radio telescopes resolution

Compared with radio telescopes, optical telescopes can resolve finer detail.

Improving resolving power

When multiple radio telescopes are used for interferometry, increasing the distance between telescopes improves resolving power.

Spitzer Space Telescope location reason

The Spitzer Space Telescope is stationed far from Earth to avoid heat from Earth.

Studying hot gas in galaxies

The best frequency range to study hot gas in the Virgo galaxy cluster is X-ray.

Studying young stars behind dust clouds

The best way to study warm young stars forming behind an interstellar dust cloud is to use infrared light.