Lecture 16 Flashcards
What are the 3 main parts of a telescope?
- collecting area
- focusing device
- detector
What is the purpose of the collecting area?
To collect incoming photons- this means a bigger collecting area is better
How does the mirror change for a focusing device?
The mirror used depends on the wavelength of light being viewed.
-visible=curved mirror
-x-ray=nested mirrors
What does the detector do?
Records the incoming photons. Visible light can be recorded by a CCD
What affects resolution?
-the size of the collecting area
-the wavelength of light
-the atmosphere (for visible light) or the ionosphere (for radio wavelengths)
-𝜃 ~ 1.22 𝜆/𝐷
What is spectroscopy?
Spectroscopy breaks light into its constituent parts
How does the Earth’s atmosphere effect astronomical imaging?
- seeing
- filters out many wavelengths
What is seeing?
The amount that objects flicker due to changes in the Earth’s atmosphere
What wavelengths can pass through the atmosphere?
Mainly visible and radio
How does exposure time affect images?
In a dark setting, a longer exposure will allow more light to be collected and produce a better image
What is a lunar eclipse?
When the Earth passes between the sun and the moon causing the Earth’s shadow to be cast on the moon
What is a solar eclipse?
When the moon passes between the sun and the earth causing the light from the sun to be blocked
What are the Saros cycles?
Every 18 years 11.3 days the Earth, moon and sun return to approximately the same geometry
