Block 1 Lesson 1

Introducing Telescopes

Why can’t we see everything with naked eye?

1. Aperture of our eyes limit amount of light that enters and therefore what we see

2. Sensitivity of our retinas limits us from seeing stuff that’s too bright or dark

Main camera vocab

Aperture

ISO

Shutter Speed

Aperture + 1 extra note + how works (X2)

Size of gap where light enters camera.

• telescope aperture is 70-200mm orbigger

Low aperture = larger opening = more light

High aperture = smaller opening = less light

ISO + how works (X2 with two points for each)

Sensitivity of sensor to light

—

Low ISO (e.g. 100 or 200):

• sensor is less sensitive to light, better for bright conditions

• clearer, less noisy images

High ISO (e.g. 1600 or 3200):

• sensor is more sensitive to light, better for darker conditions

• however, makes more noise (grainy stuff or speckles)

Shutter speed + how it works (X2)

Length of time between shutter opening and closing

—

Slow speed = more blurred photos

High speed = clearer photos

Key parts of telescope + 2 types

Eyepiece

Aperture

Objective element

—

Reflecting telescope

Refracting telescope

Eyepiece

Part you look through

Aperture + extra note

Gap where light enters

• size determines how well we view fainter objects

Objective element + extra note

The main mirror or lens of telescope

• diameter given on side of telescope

Reflecting telescope + 2 types

Telescope that uses mirror

• Cassegrain

• Newtonian

Refracting telescope + 2 types

Telescope that uses lenses

• Keplerian

• Galilean

Three main parts of convex lens diagram + 2 points

• distance between lens and principal focus is called focal length

• convex lens is drawn as a vertical line with outward facing arrows to indicate shape of the lens

Convex Lens (4 points)

• thick in middle

• converges light rays, refracts

• light rays come together at a point called the principal focus

• object appears bigger (when close to lens, if light rays haven’t started diverging yet (after passing principal focus))

Three main parts of concave lens + 2 points

• a concave lens doesn’t have an actual principal focus or focal length, we simply draw back the light rays that diverge and basically make a principal focus. this is just so it can be used for other calculations

• a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens

Concave Lens

• thin in middle

• light rays diverge, refracts

• object appears smaller

Convex Mirror

• light rays diverge, reflects

• objects look smaller, image bigger (you see more)

Concave mirror

• light rays converge, reflects

• objects look bigger, image smaller (you see less)