1. Stargazing 101 “Stargazing Equipment” Chapter 5 September 22, 2009

2. What did you see this past week? September 2009 www.OrionTelescope.com

3. Viewing the Stars 1.Naked-eye viewing 2.Binoculars 3.Telescopes

4. Viewing the Stars – Naked-eye 1.Naked-eye viewing is the best way to start Need to start with the big picture See the entire sky, piece by piece Learn the relative positions of stars and constellations to each other After awhile you will know where to look for the various stars and constellations Don’t rush into buying equipment

5. Star Brightness – Little Dipper Sky conditions affect star visibility Light pollution, moisture in air and atmospheric turbulence can make stars appear dimmer. To “rate” sky conditions on a particular night use the Little Dipper – Polaris [2.0] Compare the stars you see with the diagram What is the dimmest star you can see? Naked-eye limit is around 6 magnitude on the clearest, darkest nights Orion Catalogue Kochab

6. Viewing the Stars – Binoculars 2.Binoculars Very useful midway point between naked- eye viewing and a telescope Great way to start (before buying telescope) See more detail on the Moon See four of Jupiter’s moons Very useful for seeing open star clusters, like the Pleiades (maybe the best view), and many double stars, not visible to the naked eye Colors of stars are more evident Stars will still be points of light

7. Binoculars Binocular sizes Expressed in two numbers, such as 10x50 The first number is the magnification (or power) The second is the diameter (aperture) of the front lens, in millimeters Thus, a 10x50 binocular provides 10- times magnification and has a 50mm aperture

8. Binoculars Binocular sizes Magnification 7x or 8x – somewhat steady image, when hand-held 10x – shaky and may need to be mounted on tripod. 12x or greater, you will need to mount it on a tripod The author recommends 10x maximum Tripod mount NightWatch, p. 62-63

9. Binoculars Binocular sizes Aperture The larger the aperture (front lens) the brighter the images will appear The more light gets to your eye For stargazing, the author recommends 40- 50mm Aperture, in mm

10. Binoculars – Types There are two main types of binoculars Porro prisms Roof prisms Prisms, in binoculars, turn what would be an upside-down image, right-side up.

11. Binoculars – Binoculars – Porro prisms Porro prisms are easier to align precisely at the factory So, Porro prism binoculars tend to cost less for a given size But, they also tend to be heavier than roof prism binoculars Orion Catalogue

12. Binoculars – Roof prisms Roof prisms binoculars have a more streamlined shape Tend to be lighter Tend to be more expensive Roof prisms lose slightly more light to reflection than Porro prisms. This is a disadvantage for astronomical use Orion Catalogue

13. Binoculars – lens coatings Anti-reflection lens coatings produce much better images Increase light transmission through lens Reduce internal reflections that cause ghost images Adds to cost of good binoculars, but well worth it.

14. How to use binoculars Fix your sight on the object you want to see through the binocular. With your sight fixed on the object, move the binoculars between your eyes and the object, without looking away. Do not move your head If you don’t “nail” the object, bring the binoculars down and try again. Practice in the daytime, on a variety of objects. Harder at night, because stars look pretty much the same

15. Novel ways to steady binoculars The author recommends using: A reclining lawn chair A child-size inflatable dinghy NightWatch, p. 62

16. Selecting binoculars Some questions to consider when deciding on particular binoculars: 1.How heavy are they, for their size? 2.Are they easy or awkward to use? 3.Are they difficult to focus? 4.Are objects at the edge of the field distractingly fuzzy, even though the center of the field is in focus? 5.And, the Bottom Line: How much do you want to spend? Best to plan to spend around $100 or more

17. Selecting binoculars “Binoculars under $100” Astronomy Magazine, April 2005

18. Viewing the Stars – Telescopes Orion Catalogue

19. 3. Telescopes Three distinct types of telescopic power 1.Collecting Power (also called light gathering power or light grasp) 2.Magnifying Power 3.Resolving Power

20. 1. Collecting Power Collecting Power = the amount of light the telescope is able to focus into the eyepiece The more light it collects, the brighter the image Stars will always look like points of light, but you will be able to see more (fainter ones) and they will be brighter This is the most significant factor Explorations: An Introduction to Astronomy, Thomas T. Arny, p. 155)

21. 1. Collecting Power Light-collecting ability varies with the square of the aperture. Thus, a 90mm telescope (a little under 4”) collects only 1/5 as much light as an 8” telescope Orion Catalogue

22. 2. Magnifying Power Magnifying Power = the number of times a telescope (or binocular) can increase the apparent size of an object. 8x, 100x, etc. We’ll discuss how to calculate magnifying power later.

23. 3. Resolving Power Resolving Power = the ability of the instrument to discriminate fine detail. How sharp or fuzzy the image is The limitation on resolving power is imposed by the interaction of light and optics. The quality of the optics is a major factor Lens, mirrors, eyepieces, etc. Usually, you get what you pay for The turbulence in the air column you are looking through, moisture in the air, etc. also effect this.

24. 3. Resolving Power http://physics.uoregon.edu

25. Types of Telescopes Three basic types of telescopes 1.Refractors 2.Reflectors 3.Cassegrains (catadioptric) Maksutov-Cassegrain Schmidt-Cassegrain

26. Telescopes - Refractors 1. 1.Refractors – Use two or more lens to bend (refract) the light, so it focuses on the eyepiece at the end of the telescope. Usually the least expensive Since there are no mirrors, they can have the most distortion- free images Good for both astronomy and terrestrial viewing Other telescopes invert or reverse the image Orion Catalogue

27. How a lens focuses light A lens bends (or refracts) the light and focuses it on a point Explorations: An Introduction to Astronomy, Thomas T. Arny, p. 155) Focal Point

28. Telescopes - Refractors 60mm Refractor (2.4”) Meade model 285 Light Grasp = 4.4 sq. inches Focal length = 900mm www.meade.com

29. Telescopes - Reflectors 2. 2.Reflectors – gather light at the primary mirror (curved) on the far end of the tube, which focuses the image onto the secondary mirror (flat), that redirects the light at a right angle into the eyepiece, mounted on the side of the telescope. Orion Catalogue

30. Telescopes - Reflectors 2. 2.Reflectors Also called Newtonian Reflectors First designed by Isaac Newton, around 1670 The best light-gathering capability Quality of mirrors very critical Good for astronomy viewing only They invert the image (objects look upside down) Orion Catalogue

31. How a curved mirror focuses light Mirrors that are made of glass that has been shaped to a smooth curve, polished and then coated with a thin layer of aluminum or some other highly reflective material Explorations: An Introduction to Astronomy, Thomas T. Arny, p. 158) Focal Point

32. Telescopes - Reflectors 6 inch Reflector Orion® AstroView TM 6 EQ Reflector Light Grasp = 27.4 sq. inches Focal length = 750 mm Weight = 39 pounds (telescope and tripod) Orion Catalogue

33. Telescopes - Reflectors 10 inch Reflector Orion® Atlas 10 EQ Light Grasp = 78.5 sq. inches Focal length = 1200 mm Weight = 117 pounds (telescope and tripod) Orion Catalogue

34. Telescopes – Reflectors Dobsonian mounts were designed for larger reflectors that were too unstable on tripods. They sit on the ground Simple structures with Teflon bearings that provide smooth vertical/horizontal movement Lighter than tripods Orion Catalogue

35. Telescopes - Reflectors 8 inch Reflector Orion® SkyQuest TM XT8 IntelliScope® Light Grasp = 50.2 sq. inches Focal length = 1200 mm Weight = 41.6 pounds (telescope and tripod) Orion Catalogue

36. Telescopes - Cassegrains 3. 3.Cassegrains – have a compact tube which incorporates primary and secondary mirrors that fold the light path and focus the light into the eyepiece at the end of the tube. Orion Catalogue

37. Telescopes - Cassegrains 3. 3.Cassegrains (catadioptric) Maksutov-Cassegrain Schmidt-Cassegrain Shorter and lighter than the others Tend to be more expensive Good for both astronomy and terrestrial viewing Image is right side up but reversed left to right. Orion Catalogue

38. UFO Telescope Meade LX200R 12” 305 mm (12 in.) Advanced Ritchey- Chrétien optical design Focal length = 3048 mm Weight = 125 lbs. (telescope and tripod) www.meade.com

39. Telescopes – Eyepieces An eyepiece brings the light rays gathered by the telescope into sharp focus. The eyepiece determines the magnification, as well as its brightness and contrast Your eye Orion Catalogue

40. Telescopes – Eyepieces Eyepieces with shorter focal lengths (lower numbers) provide higher magnifications Ex. 4 mm to 12 mm focal length Images under high magnifications become more and more fuzzy, depending on the quality of the optics

41. Telescopes – Eyepieces Eyepieces with longer focal lengths (larger numbers) provide lower magnification, but yield brighter, sharper images Ex. 20 mm to 40 mm (wider angle)

42. Telescopes – Eyepieces Eyepieces Medium Lengths 13 mm to 19 mm The author recommends having at least one low (20-40 mm) and one medium (12-19 mm) power eyepiece.

43. Calculating Magnification Magnification = Telescope focal length Eyepiece focal length Telescope focal length = The distance from the center of a curved mirror or the center of the lens (where light passes through the first element of the telescope) to the focal point. Orion Catalogue Orion AstroView Meade LX200R

44. Calculating Magnification Magnification = Telescope focal length Eyepiece focal length Eyepiece focal length = The distance from the center of the field lens (where light passes through the first element of the eyepiece) to the focal point. Given in millimeters ex. 25 mm, 14 mm, 7.5 mm) Orion Catalogue

45. Calculating Magnification Magnification = Telescope focal length Eyepiece focal length Examples 750 mm = 30x (my telescope) 25 mm 3048 mm = 122x (12” Meade) 25 mm OR 750 mm = 100x (my telescope) 7.5mm 3048 mm = 406x (12” Meade) 7.5 mm

46. Calculating Magnification Magnification = Telescope focal length Eyepiece focal length Eyepieces for Meade LX200R 12” 3048 mm = 117x 26 mm 3048 mm = 218x 14 mm

47. Telescopes – Eye Relief Eye Relief is the distance between your eye and the eyepiece lens, when the image is in focus Eyeglass wearers need at least 15mm Orion Catalogue

48. Telescopes – Eye Relief Shorter focal-length eyepieces tend to have shorter eye relief than longer focal length eyepieces. Smaller lens openings You need to get closer to them to see the image Like looking through a peek- hole. 17mm6 mm NightWatch, p. 76 Orion Catalogue

49. Telescopes – Eye Relief Eye Relief can be improved Larger eyepiece lens openings to make it easier to see the image with your eye farther away Much more comfortable viewing These eyepieces will be more expensive 3.8mm9.5mm Orion Catalogue

50. Telescopes – Barlow lens Barlow lens is a simple, relatively inexpensive lens which doubles or triples the magnifying power of a given lens. Orion Catalogue

51. Telescopes – Finder scopes Finder scopes are miniature telescopes mounted parallel to the main tube that allow easy alignment of the target object. Object is centered in the crosshairs of finder scope Has to be adjusted to the main telescope NightWatch, p. 67 Finder scopeEyepiece

52. Telescopes – Tripods/Mounts A sturdy tripod and mount are essential to jiggle-free viewing Especially at higher magnifications The slightest movement is greatly magnified The mount also has to be able to smoothly adjust for the Earth’s rotation Especially at higher magnifications The objects move quickly through the field of view

53. Telescopes – Tripods/Mounts Altazimuth Mount Up and down (altitude), and left and right (azimuth – around the horizon) rotation controls This model has slow- movement cable controls Least expensive Mount Tripod Orion Catalogue

54. Telescopes – Mounts Equatorial Mount The polar axis on the mount is aligned toward Polaris Then you only have to turn a single knob to compensate for the Earth’s rotation NightWatch, p. 67Orion Catalogue

55. Accessories Electronic drive systems compensate for the rotation of the Earth and keep the image centered in the telescope Single axis and dual axis drives are available www.meade.com

56. Accessories “Go to” computer controllers A computer is built into the telescope base Once the computer is aligned, the system is able to find thousands of celestial objects Ex. Meade AutoStar II – has a 145,000 celestial object database www.meade.com

57. Accessories Filters Moon – too bright when more than half the moon is lighted Planets – different colors enhance the image Sun – large filter that goes over the front opening Otherwise, you could “cook” the inside of the telescope Orion Catalogue

58. Telescope – lens coatings Anti-reflection lens coatings produce much better images Increase light transmission through lens Reduce internal reflections Meade Ultra-High Transmission Coatings (UHTC) Increases brightness by nearly 20% over their other lens coatings

59. Selecting Telescopes How much do you have to spend? The author says that if you can not spend at least $300, your best bet is to buy a good pair of binoculars and wait until you have more money to spend on a telescope So you don’t get the ”Trash-Scope Blues” (p. 65)

60. Selecting Telescopes The author has good comments: “Telescope comparisons” (p. 80) “Factors to consider when selecting a first telescope” (p. 81) “Trash-Scope Blues” (p.65)

61. Clear Sky Clock Transparency = total transparency of the atmosphere from ground to space Calculated from the total amount of water vapor in the air Seeing = being able to see fine detail at high magnifications Bad seeing is caused by turbulence, combined with temperature differences in the atmosphere http://www.cleardarksky.com Set for Dayton, Ohio or where ever you want http://www.cleardarksky.com/c/Dayton_OHkey.html?1

62. Accuweather “Satellite” view http://wwwa.accuweather.com/index- forecast.asp?partner=accuweather&traveler=0& zipcode=45409&u=1http://wwwa.accuweather.com/index- forecast.asp?partner=accuweather&traveler=0& zipcode=45409&u=1 “Map in motion” to see how the clouds are moving Can see if clouds are present and if they will be moving in or out

63. Websites Celestron Telescopes http://www.celestron.com/main.php Meade Telescopes http://www.meade.com Orion Telescopes and Binoculars http://www.telescope.com Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.html Hubble Site http://hubblesite.org NASA http://www.nasa.gov/home/index.html

64. Autumnal Equinox The Autumnal Equinox occurred earlier today, September 22, 5:18 pm (EDT) “When the Sun crosses the equator heading south for the year. This event marks the start of Fall in the northern hemisphere.” (StarDate Magazine, January/February 2007) The length of day and night are the same (almost – Sunrise 7:24 am, Sunset 7:33 pm) Why? The Sun rises due the east and sets due west StarDate.org (September 21, 2009) Track #46

65. Biology: Concepts and Connections, 5th ed. Benjamin Cummings Autumnal Equinox