Review for Final Examination (Astronomy Labs) --------------------------------------------- ***I will be giving out the final exam at 7:30 PM on Monday, Tuesday, Wednesday, & Thursday in 50/1300... If you can't make it to one of those evenings, PLEASE let me know so we can arrange another day for you to take the final exam. YOU MUST TAKE THE FINAL EXAM BEFORE THE END OF THE SEMESTER TO PASS THIS COURSE!!! 1. Know the definition of the following terms: Ecliptic, Zenith, Horizon, Meridian, Celestial Sphere, Celestial Equator, North Celestial Pole, South Celestial Pole, Right Ascension, Declination, Sidereal Period, Synodic Period, Circumpolar Constellations, Circumpolar Stars, Astronomical Unit, Light Year, Ellipse, Major Axis, Semi-Major Axis, Minor Axis, Semi-Minor Axis, Eccentricity, Virtual Image, Real Image, Refracting Telescope, Reflecting Telescope, Geocentric Viewpoint, Heliocentric Viewpoint. (I think that would be enough terms to remember for one test; don't you think?) 2. Again, I will ask you questions about the Moon: phases, rising, on the meridian, and setting. Please look over your quizzes and midterm plus the in class exercise as well. REMEMBER, the phase of the Moon would tell us where the Sun is and once we know where the Sun is in the sky, we know what time it is base on the Sun's location, not the location of the Moon! 3. Know how to calculate the magnification power of a telescope if the focal length of the objective lens/mirror and the focal length of the eye- piece are given. Also, be able to compute the "maximum effective magnification," focal ratio, light gathering power, total focal length of a telescope if a biconcave lens is used as an eyepiece or a biconvex lens is used as an eyepiece. Again, please look over the T-1 lab that we did and questions that I asked you from the first midterm. 4. Understand the "ray tracing" technique and be able to indicate where the image is by using that method. If the object is farther from the center of the lens than the front focal length, then the image which is real/positive is on the other side of the lens and up-side-down as well. However, if the object is closer than the front focal length, then you will end up with the image on the same side of the object with upright--virtual image/negative. Make sure that you can perform both, real and virtual. Once you have figured out where the image is, then you can calculate the Magnification Power of the lens by using the following equation: MP = i / o = H(image) / H(object) where i is the distance from image to center of the lens, o is the distance from object to center of the lens, H(image) is the height of the image, H(object) is the height of the object. But there is a problem with lenses where all wavelengths don't come to the same focus after refracting through the lens. Blue wavelength comes to focus faster than red wavelength. This is known as Chromatic Aberration and to fix it, just place a second lens making from a different material than the first one behind the first/objective lens. Now, both blue and green wavelengths come to the same focus whereas red and yellow wavelengths come to another focus further out. But because our eyes are sensitive to red so we tend to focus in red and leave the blue out of focus... This is known as Achromatic Aberration--Achromatic Lens. For mirrors, if the shape of the mirror is in spherical, then all the light rays don't come to the same focus so it is a Spherical Aberration. To fix that, just grind or polish the mirror into parabola. Light rays hitting a parabola surface are coming to a same focus. 5. Now, there is another way to figure out the Magnification Power of a telescope. MP = FL / fl where FL is the focal length of the objective lens/mirror, fl is the focal length of the eyepiece. Since FL is a fix value, depending on the shape of the lens/mirror, to increase MP, one has to use a lower fl or vice versa. However, you can only magnify your telescope up to a certain point and if you try to go beyond that, you will either not get enough light to your telescope or the image can't be focused. This is known as "the Maximum Effective Magnification" or MP(max) = 20X * D(cm) where D is the diameter of the objective lens/mirror in centimeters!!! What if you have D in millimeters, can you still use the equation above without converting D from mm to cm? YES, you can! Can you figure out a way to do that??? Also, the total Focal Length of a telescope depends on what eyepiece you are using. *For a biconvex eyepiece, FL(total) = FL + fl *For a biconcave eyepiece, FL(total) = FL - fl Furthermore, one can figure out the Focal Ratio of a giving telescope by F/ = FL / D where FL is the focal length of the objective lens/mirror, D is the diameter of the objective lens/mirror in the same unit as FL. The Focal Ratio is a value which uses to determine whether the telescope is "fast" or "slow." (It has the same meaning as your camera...) 6. Be able to identify different type of reflecting telescopes: Primary Focus, Newtonian Focus, Cassegrain Focus, Schmidt-Cassegrain Focus, and Coude Focus. Which type of telescope would give you a long focal length, short focal length, large field of view, small field of view, etc.? Also, know all the parts that make up each type of telescope: primary mirror, secondary mirror, flat mirror, focus (eyepiece), and focal length. 7. For the "Colors and Spectra" exercise, know the difference between apparent magnitude, m, and absolute visual magnitude, M(v). Also, be able to list the spectral types/classes from hottest to coolest: O B A F G K M. In addition, be able to identify which star is hotter if the color is giving... But here is a table that you may want to consider looking over again! Spectral Types -------------- Spectral Surface Temperature Classes (Kelvins) Colors -------- ----------- ------ O > 30,000 Deep Blue B 20,000 Blue A 10,000 White F 7,500 Light Yellow G 5,500 Yellow K 4,500 Orange M < 3,500 Red In other words, O stars or deep blue stars are the hottest while M stars or red stars are the coolest. If two stars happen to have the same color, then they both should have similar surface temperature or vice versa. On the other hand, bright star has a "small" number while dim star has a "large" number, i.e., star with magnitude of 1 is 2.5 times brighter than a star with magnitude of 2... In addition, know the formula below, Distance Indicator: m - M(v) = -5 + 5*log(d) where m - M(v) is known as "distance modulus," d is the distance of a star in pc, "parallax per second" (not Personal Computer!). *Apparent magnitude, m, tells us how bright a star looks. *Absolute visual magnitude, M(v), is the apparent visual magnitude of the star if it were 10 pc away, where 1 pc (parsec) is equal to 3.26 light-year. Also, know the "constructive interference" or bright-line formula, n * lambda = d * sin(theta) where n is the order of diffraction (a positive integer), lambda is the wavelength of the light (usually in nm), d is the interslit distance (same unit as lambda), theta is the angle of diffracted beam. Giving a wavelength of the light and the interslit distance, be able to compute to see how many orders of diffractions by utilizing this relationship, n * lambda