~Introduction

-1st non-magical telescope invented 70 years after von Rheticus(1608)
-von Rheticus telescope has as much resolving power as 12-cm-wide Muggle telsecope(1 arcsecond) but less than 1/20 the light-gathering power
-Muggles' best telescopes far superior to ours due to technology advance
-They can make more accurate measurements of angular size, optical albedo, and distance from sun
-100-in wide Hubble telescope has 20x as much resolving power as von Rheticus telescope
-Newer von Rheticus model too expensive for most First-Years

~Distance From Sun

-Planet's distance from sun not constant due to elliptical revolving around sun
-Can research calculations from Muggle sources

~Angular Size, Phase, and Optical Albedo

-Moon and some planets have lighter/darker parts with different specific albedos
-Albedo of ea. celestial body constant
-Angular size depends on planet's distance from earth, which varies
-Venus has widest range of angular size(appears 6.8 times as large when it's closest to earth as when it's farthest away)
-Table:
Celestial Body - Albedo - Angular Size(arcminutes'/arcseconds")
Sun - N/A - 31'27"-32'32"
Moon - 0.110 - 29'20"-34'6"
Mercury - 0.088 - 4.5"-13.0"
Venus - 0.760 - 9.7"-1'6"
Mars - 0.250 - 3.5"-25.1"
Jupiter - 0.503 - 29.8"-50.1"
Saturn - 0.342 - 14.5"-20.1"
Uranus - 0.300 - 3.3"-4.1"
Neptune - 0.290 - 2.2"-2.4"

-Besides using a table, you can use 2 zoom buttons on the top of the wider tube near the middle of the telescope, when the focus knob is on the left.
-That way you can zoom without jarring telescope
-One button is labeled S for angular size. When pressed, it shows the angular size of the object(in degrees, arcminutes, and arcseconds) in red at the bottom of the view
-Degrees=o, arcminutes=', arcseconds="
-If object isn't round, then greatest dimension is angular size
-Ex: Looking at comet, who has the angular length of 2 degrees, 35 arcminutes, and 28 arcseconds, you'll see 2o35'28"
-Comet's length much greater than width
-If angular size is less than 1 degree, then only arcminutes/arcseconds are shown
-If it's less than 1 arcminute, only number of arcseconds is shown.
-If object is too wide to see even at min. magnification, press S button with 1 end of the bject in the field of view and hold while scanning entire object
-Calculates angular size by measuring angular size of object and dividing by magnification
-Von Rheticus telescope calculates phase by measuring angular length and width and dividing width by length
-Only true value if no light is blocked from Earth
-Other button labeled A for albedo(in old version).
-When pressed, the optical albedo(a number between 0 and 1) appears in red characters below object as long as button is pressed
-You'll see average albedo of either entire object or just the part that you can see
-albedo harder to measure than angular size
-amount of light=angular size^2*albedo*phase/distance from Sun^2
Or in words, the amount of light equals the angular size squared, times albedo, times phase, divided by the distance from Sun squared
-Value only good if body is familiar(planets or moon), orbit of planet is circular, and phase isn't a result of part of the light being blocked

~Interference and Magical Albedo

-Magical components
-To calculate interference, measure the angular separation between target and each of the other objects in the sky
-You need the relative strength of the magic reflected by each of the other bodies compared to the magic reflected by target itself
-To calculate magic albedo from optical albedo, know what surface is made of(usually same as optical albedo)
-Rocky surface only reflects about half as much magic as light
-Water and ice cuts magical albedo in half again as it absorbs sun's magic
-The A button on the new von Rheticus model calculates A.M.E. quotient from the intensity of the magic it detects and displays it in pure red

~Assignments

-Mandatory quiz
-Extra-credit essay