Telescopes

Question 1

What are the 2 types of telescopes

Answer 1

• Refracting Telescopes (Lenses)
• Reflecting Telescopes (Mirrors)

Question 2

What is the equation for

Separation of 2 points in the sky

Answer 2

ℓ = f α

ℓ = distance between 2 points, f = focal length, α = angle separation

Question 3

What is

Focal ratio

Answer 3

• Ratio of focal length to lens diameter
• “f/8” = 8

f = focal length, D = Diameter of lens

Question 4

What is the equation for

The amount of power a telescope receives per unit area

Answer 4

(πS_B)/4(f/D)^2

S_B = surface brightness, f/D = focal ratio

Question 5

What is the

Diffraction Limit

Answer 5

• Smallest angle between 2 stars, where you can still distinguish 2 separate stars (not a single merged star)
• α_min = 1.22λ/D
• This limit is for circular apertures

α = angular resolution, λ = wavelength of light, D = Lens Diameter

Question 6

Facts about

Visual observing using eyepieces

Answer 6

• Eyepiece makes light parallel so the eye can see it
• Provides angular magnification
• M = α_2/ α_1 = f_1 /f_2

M = angular magnification, α = angular separation, f = focal length