Telescopes

2. The brightness of an astronomical object is designated by its _______________. A telescope which gathers more light will be able to see _______________ objects. See section about transparency if you are unsure of the answers.

3. A difference of five magnitudes between two stars is equivalent to an intensity difference of _______________. Therefore the intensity difference between two stars separated by a brightness difference of one magnitude is equivalent to _______________.

4. The more positive the magnitude of an object the BRIGHTER/FAINTER (circle one) it becomes.

5. Another word for the size of the lens or mirror is its _______________.

6. The distance that light must travel before coming to a focus is called a telescope's _______________.

7. The diameter of the lens or mirror divided into the distance that the light must travel before it comes to a focus is termed the telescope's ________________.

8. The ratio of the size of an image as viewed through the telescope, compared to its naked eye appearance, is the _______________ which the telescope produces.

9. The focal length of a telescope divided by the focal length of the eyepiece mathematically defines a telescope's _______________.

10. A 48-inch focal length instrument uses a ½ inch eyepiece to produce a magnification of _______________.

11. Telescopes must be able to separate objects of close angular measure. This is called a telescope's ________________.

12. The ability of a telescope to separate objects of close angular measure depends most critically on the telescope's _______________

13. The formula for the Dawes limit for resolution equals

___________________________________________________________________.

14. The theoretical resolution based upon Dawes' limit for the 200-inch Hale reflector on Mt. Palomar is _______________.

15. To be able to distinguish various shades of gray or color hues, a telescope must be able to produce images with acceptable _______________.

16. Clarity or sharpness of an image relates to the quality of the optics in the telescope and is called _______________.

17. The angular diameter of the sky which is visible through an eyepiece is called the ____________________.

*18. The field of view produced at the eyepiece of a telescope having a 48-inch focal length and using an eyepiece of ½ inch focal length with a 50 degree apparent field would be _______________.

19. Steadiness of the atmosphere is referred to as ______________.

20. For observers in the Northeastern United States, the season of the year which produces the steadiest atmospheric conditions is _______________.

21. The clarity of the atmosphere, as it relates to the faintest stars that can be observed at one's zenith, is called _______________.

22. Usually on cold, windy, winter nights the _______________ can be excellent, but the _______________ is usually horrible.

23. Why is it impossible for large telescopes to reach their theoretical potential for resolution? _______________________________________________________________________

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24. When a star is examined critically in a good telescope, it appears to be composed of a disk surrounded by a series of rings. The name of the disk is called the _______________ disk.

*25. The size of the false disk of a telescopically viewed star image is related inversely to the _______________ of the telescope. In other words, the larger the telescope mirror or lens, the BIGGER/SMALLER (circle one) the false disk.

*26. Why is it normally possible to use higher magnification with a larger aperture telescope. ______________________________________________________________________

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*27. As more light is concentrated into the rings surrounding the diffraction disks which compose an image, the image begins to suffer by losing _______________.

*28. When light passes very near an obstruction it will be slightly _______________ from its straight path direction. This phenomenon is known as _______________ and is a good/bad (circle one) situation.

*29. Why does the contrast of a telescopic image decrease as the diameter of the obstructions, encountered by the light, increase?

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*30. Why does the contrast of an image decrease as the optical components of a telescope decrease in accuracy?

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*31. Why do stars have spikes, or appear "starlike" in some telescopes, while other instruments produce disk-like images?

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*32. A telescope mirror or optical system is rated against the standard wavelength reference which is _______________.

*33. An Angstrom equals what fraction of an inch or centimeter? ____________________

*34. The maximum acceptable deviation at the focal plane for an astronomically acceptable image is _______________.

THE LAWS OF LIGHT

35. A line segment which is perpendicular to an optical surface is called a _______________.

36. The law of _______________ states that with respect to a normal, the angle of incidence of an approaching light beam will equal the angle of reflection.

37. When light travels from a less dense medium into a medium of greater density, the light ray will be bent _______________ the normal.

*38. The formula sin i = n sin r is the mathematical representation for law of _______________, where "i" equals the angle of _______________, "r" equals the angle of _______________ and "n" equals the index of _______________ for the denser medium.

39. The entire array of energy from gamma radiation to the radio frequencies is called the _______________ spectrum.

40. The frequencies of energy to which the eye responds are called _______________ light.

41. _______________ and ______________ are two descriptive methods of representing the entire array of energy from gamma radiation to radio.

42. The simple bending of one wavelength of light as it moves through mediums of different densities is called _______________.

43. When each component of white light is selectively bent as it is transmitted through a prism or lens, the effect is called _______________.

DIFFERENT TYPES OF TELESCOPES

44. The lens or mirror which gathers the light in a telescope is normally designated as the _______________.

45. A telescope employing only lenses is referred to as a _______________.

46. A telescope employing only mirrors is called a _______________.

47. A compact telescope, possessing mirrors and a lens is referred to as a _________________ system.

48. The inventor of the telescope was a Dutch lens grinder who made a "spectacle" of himself. His name was ____________________.

49. The name of the first person to turn a telescope towards the heavens was ________________.

50. A double convex or single element lens produces a defect or aberration at the focus of a refractor called _______________ aberration.

51. The introduction of a second lens with a different index of refraction causes the problem mentioned in the last statement to become less noticeable. The shape of this lens is ______________________________.

52. A double element refractor is often called an _______________ refractor. *The first element is usually referred to as the _______________, while the second lens is often called the _______________ as a result of the different types of glass which go into the making of these lenses.

53. The first individual to construct a reflecting telescope was named ____________________. His interest in mirrors, rather than a lens to collect light stemmed from his desire to free images from _________________________.

54. A smaller wide-field telescope which has its optical axis aligned to the main instrument is called a _______________.

55. The part of a telescope which does most of the magnification of the image is referred to as the _______________.

56. This apparatus, called a _______________, supports the telescope tube assembly and allows it to be pointed to any location in the sky.

57. This device supports the secondary mirror in an open tube reflector and is known as a _______________.

58. The simplest and least expensive type of reflector to construct is called a _______________.

59. These telescopes (answer to last question) are wonderful when made in short to medium focal lengths. What disadvantage occurs when they are constructed in long focal lengths? _______________________________________________________________________

60. When the shape of the mirror in a reflector is a _______________, light which strikes in the vicinity of the edge of the mirror comes to a focus closer to the mirror than light striking the mirror nearer to the optical axis.

61. The optical defect mentioned in the last statement is called ___________________________.

62. The problem mentioned above can be corrected by changing the curvature of the mirror into a _______________.

*63. An optical problem which can be the result of the exposure of the lens or mirror to a rapid change in temperature is called _______________. As the mirror or lens cools, its curvature may change, causing different portions of the objective to focus its light at slightly different positions.

64. A _______________ type of reflecting telescope employs a convex secondary mirror, but no corrector.

65. The secondary mirror of the type of telescope mentioned above serves to increase the _______________ of the telescope without increasing the tube size.

66. With reference to a reflector employing a concave primary and a convex secondary, the primary mirror has a LONG/SHORT (circle one) focal length?

67. The eyepiece position for this compound reflector, mentioned in the last question, is found IN FRONT/IN BACK (circle one) of the mirror

68. A long focal length reflector which has an ultrashort tube length and uses a lens called a corrector or meniscus to help form the image is called a c . .

69. Specifically, a _________________________ reflector uses a corrector plate while a _________________________ reflector uses a meniscus.

70. The shape to which the primary mirror is ground and polished in telescopes that use lenses and mirrors is called a _______________. It is virtually impossible to parabolize mirrors with focal ratios of F/3 or less, but it is possible to grind and polish such short focal ratios with a spherical curvature.

71. Without the corrector the images brought to a focus by these ultracompact telescopes would suffer from _______________ aberration.

72. Think of the corrector as adding the necessary p to the image to bring about a sharp precise focus.

*73. An ultrashort focal length catadioptric reflector designed specifically for photographic purposes is called a ____________________. Such an instrument is constructed primarily for patrol work in which SMALL/LARGE (circle one) regions of the sky need to be surveyed for new supernovas, comets, or the making of star maps.

74. A very short focal length Newtonian reflector can go by the name of a _______________ telescope. This is because it provides a large/small (circle one) field of view.