5. The brightest planet Venus will be less than 1/6 moon distance from the fainter planet Saturn! Get up early and see this conjunction! This will be the closest any 2 planets have been together since 2013

7. # 41 from the Messier Catalog is an open-cluster of stars in the Canis Major Constellation. The cluster Is about 4 degrees almost exactly south of Sirius It contains about 100 stars In an area roughly the size of a full Moon. Several of which are “Red Giants” It is estimated to be aprox 190 million years old, with a lifetime expectation of aprox 500 million years!

14. History Lenses and hardware Reflecting telescopes Refracting Telescopes

15.  Hans Lippershey Middleburg, Holland  invented the refractor telescope in 1608  Galileo  the first to use a telescope in astronomy. Galileo's designs used a combination of convex and concave lenses.  Kepler  improved the design to have two convex lenses, which made the image upside-down. Kepler's design is still the major design of refractors today, with a few later improvements in the lenses and the glass to make them.

16. The answer is simple: the object does not take up much space on your eye’s screen ( retina). Using a digital camera analogy, at 150 feet the writing on a dime does not cover enough pixels on your retinal sensor for you to read the writing. This can be corrected by bending the light with lenses.

17.  The lens in your eyes works like a glass lens. The light bends as it goes through a different medium.  Light rays are bent when they intersect glass; a curved surface can produce an image.  In your eye, the image is then focused at the retina.

18.  If you had a bigger eye, you could collect more light from the object. This image could be magnified so it stretches out over more pixels in your retina.  In a telescope, two pieces make this possible:  the objective lens (refractor telescopes) or primary mirror (reflecting telescopes)  the eye piece

19. The objective lens (in refractors) or primary mirror (in reflectors) collects lots of light from a distant object and brings that light, or image, to a point or focus. An eyepiece lens takes the bright light from the focus of the objective lens or primary mirror and "spreads it out" (magnifies it) to take up a large portion of the retina. This is the same principle that a magnifying glass (lens) uses; it takes a small image on the paper and spreads it out over the retina of your eye so that it looks big.

20. Diagram of a simple telescope. Parallel light rays enter from the left, pass through the objective lens, come to a focus at the focal plane, and exit through the eyepiece lens. The focal length of the objective is F, and the focal length of the eyepiece is f.

21. When you combine the objective lens or primary mirror with the eyepiece, you have a telescope. Again, the basic idea is to collect lots of light to form a bright image inside the telescope, and then use something like a magnifying glass to magnify (enlarge) that bright image so that it takes up a lot of space on your retina.

22.  how well it can collect the light (the aperature)  how much it can magnify the image (the magnification)

23.  A telescope's ability to collect light is directly related to the diameter of the lens or mirror -- the aperture -- that is used to gather light. Generally, the larger the aperture, the more light the telescope collects and brings to focus, and the brighter the final image.

24.  The telescope's magnification, its ability to enlarge an image, depends on the combination of lenses used. The eyepiece performs the magnification. Since any magnification can be achieved by almost any telescope by using different eyepieces, aperture is a more important feature than magnification

25. View through an eyepiece. Note that the image is upside- down.

26. The purposes of the eyepiece are to:  produce and allow you to change the telescope's magnification  produce a sharp image  provide comfortable eye relief (the distance between your eye and the eyepiece when the image is in focus)  determine the telescope's field of view:  apparent - how much of the sky, in degrees, is seen edge-to- edge through the eyepiece alone (specified on the eyepiece)  true or real - how much of the sky can be seen when that eyepiece is placed in the telescope (true field = apparent field/magnification)

27. Filters are pieces of glass or plastic that you can place in the barrel of an eyepiece to restrict the wavelengths of light that come through in the image. Set of filters for viewing, including a light pollution filter (left) and colored filters for enhancing contrast in planetary images. Filters can be used to:  enhance the viewing of faint sky objects in light-polluted skies  enhance the contrast of fine features and details on the moon and planets  safely view the sun

28.  Refractor telescopes, which use glass lenses  Reflector telescopes, which use mirrors instead of lenses. Both types accomplish exactly the same thing, but in completely different ways.

29.  Refractors are the type of telescope that most of us are familiar with. They have the following parts:  a long tube, made of metal, plastic, or wood  a glass combination lens at the front end ( objective lens )  a second glass combination lens ( eyepiece )  Refracting telescopes focus light rays by bending them with glass.

30. This is the simplest telescope design you could have. A big lens gathers the light and directs it to a focal point and a small lens brings the image to your eye.

31. Refracting telescopes are not used for astronomical research (anymore) because they are large and have heavy lenses (i.e. expensive).

34. “Chromatic Aberration” occurs because Red and Blue light have different wavelengths. They can not come to focus on a lens at exactly the same point. This will cause a ring of false color around point sources of light and results in general blurriness to an image Visible light entering objective lens fFocal point

36.  History:  Isaac Newton developed the reflector about 1680, in response to the chromatic aberration (rainbow halo) problem that plagued refractors during his time. Instead of using a lens to gather light, Newton used a curved, metal mirror (primary mirror) to collect the light and reflect it to a focus. Because the mirror reflected light back into the tube, he had to use a small, flat mirror (secondary mirror) in the focal path of the primary mirror to deflect the image out through the side of the tube, to the eyepiece; otherwise, his head would get in the way of incoming light.  In 1722, John Hadley developed a design that used parabolic mirrors, and there were various improvements in mirror-making. The Newtonian reflector was a highly successful design, and remains one of the most popular telescope designs in use today.

37. This solved the problem of colored rings, and other problems as well

40. They use mirrors, not lenses so they are free of Chromatic aberration Newtonian telescopes are usually less expensive for any given objective diameter (or aperture) than comparable quality telescopes of other typesaperture Since there is only one surface that needs to be ground and polished into a complex shape, overall fabrication is much simpler than other telescope designs A short focal ratio can be more easily obtained, leading to wider field of viewfocal ratiofield of view The eyepiece is located at the top end of the telescope. Combined with short f-ratios this can allow for a much more compact mounting system, reducing cost and adding to portabilityratios

43. The “spider” supports the Secondary mirror. Because it is In the path of the incoming light It blocks some of it, and can cause Distortion in the image Visually this can be corrected or Diminished by using a 2 or 3 legged spider

44. Collomation is the procedure to align the primary and secondary mirrors. It can be VERY TIME CONSUMING on an inexpensive reflector telescope And requires special tools and a lot of patience

45. Another version of the Reflector Telescope is the infamous “Bird – Jones” It uses an inexpensive and poor quality spherical flat shaped primary mirror. There is an additional “corrector” lens added to the eyepiece focuser tube to compensate for a shorter tube length, which allows the Manufacturers to make them less Expensive. This style of telescope is almost Impossible to collimate and the image quality is very very poor.

46. The Catadioptric Telescope is a hybrid that uses both mirrors and lenses. Light passes through a lens to the primary mirror, and is then reflected To the secondary mirror, and finally reflected to the focuser tube eyepiece There are 2 very popular styles of this design, the Schmidt-Cassegrain And the Muskatov Cassegrain. Both are relatively similar and are by far the Most popular modern telescopes being sold

47. Most versatile type of telescope Best near focus capability of any type telescope First-rate for deep sky observing or astrophotography with fast films or CCD's Excellent for lunar, planetary and binary star observing plus terrestrial viewing and photography Closed tube design reduces image degrading air currents Compact and durable

48. More expensive than reflectors of equal aperture Its appearance may not be suited to everybody's taste Slight light loss due to secondary mirror obstruction compared to refractors

50.  Many modern day telescopes do not use visible light to collect images.  Radio telescopes, x-ray telescopes and infrared (IR) telescopes have become a staple of modern day astronomy, producing some amazing images. www.yorku.ca/eye/spectrum.gif

51. *What is your budget? Are you more interested in astro-photography or Visual observing? Some telescopes are much more suited for one or the other, while a few can serve both purposes OK but not as well as one designed for either Purpose Avoid department store telescopes. Typically they speak about “THE POWER” of magnification. There is no merit to an image which is gigantic and out of focus. We care about clarity first, not magnification. Read reviews! You will learn a lot based upon what others have spent their Money on. Go to star parties, and use the different types, see which suits you.

52. There is more to the telescope than the optical Tube assembly! The style of mount you choose can be either A blessing or a curse, depending upon your Intentions (photography or visual observing) We will discuss the various mounts and their Advantages/ disadvantages in another presentation