Block 1 Lesson 2

More Telescopes!

What is Light Grasp + note

How much light reaches the objective element.

• As objective element doubles, light grasp quadruples

Light grasp equation + unit

light grasp = objective element diameter squared

Unit = mm or whatever given

How are light grasp and diameter of objective element related to each other?

Proportional.

As the diameter of the objective element increases, so does the light grasp.

What is FoV

FoV (field of view) is the angle or diameter of the sky that can be seen through a telescope.

Human FoV is 180°

FoV equation + unit

FoV = (angular separation X diameter of image) / distance between objects

Unit = degree°, arcmin’, arcsec”

How do degrees, arcmin and arcsec work + unit

1 degree = 60 arcmin = 3600 arcsec (multiply by 60 each time)

°, ‘, “

What is angular separation

How far the two objects appear to be in the sky as we look up

Angular Separation equation + units + what each part of equation means

Ang sep = (FoV X distance between objects) / diameter of image

Units = degrees, arcmin or arcsec (whatever is given in question, will say FoV is — and that’s the unit)

Ang sep = How far the two objects appear to be in the sky as we look up

FoV = how much of the sky the telescope can see

Distance between objects = in picture

Diameter of image = size of picture

Magnification equation + unit

Magnification = focal length of objective element / focal length of eyepiece

M = fo / fe

Unit = no unit but you put an ‘X’ after the number e.g. 42X

Unit for either focal length if asking for them = mm

How to remember magnification equation

Like ‘comfy’ but ‘foMfe’. fo is at top of triangle, then M on left and fe on right