The joys of viewing the night sky are only enhanced if you have a telescope, and know how to use one. Binoculars bring out a great deal more, letting you examine a little more closely the grand canopy of stars you have been feasting with your unaided eyes. Telescopes greatly narrow your field of view. Instead of beholding the vastness spread out from your right to your left, you close in on a very small spot. Eyes alone allow you to see over half of the entire sky at once, available to you at any one time. The sky above, which is referred to as the “celestial dome” and is like peering inside an upside-down bowl, measures 180 degrees from one side to the other. Binoculars narrow that field to about seven degrees, or a bit more than the angular distance between the front stars of the Big Dipper. A telescope magnifying at least 30x diminishes that field of view to about one degree, or less depending on the magnification you select by switching eyepieces. The Moon is about one-half degree in angular width. Your little “finder” scope attached to the main telescope tube needs to be properly aligned. This is so the star or planet or other object you are trying to see, will be seen with your main telescope when it is centered in the finder view. Use it to point your telescope; begin with low magnification. Low power eyepieces may have a field of view of about a degree. If your targeting is a little off, you still might have that star or planet in sight in the low power view, albeit a bit off-center. You may then switch to a higher power eyepiece, being careful not to knock the telescope even slightly. You will have to re-focus your instrument. Higher magnification allows a closer look but your star or planet will run away on you quicker! The whole sky appears to revolve around you east to west, as the Earth turns around. The more magnification you use, the more pronounced is this affect. If you have reflector telescope, on a chilly night it is best to set it outside for an hour or so before you observe. This lets the the warmer air in the tube flow out, so that the warm air currents don’t spoil your views, especially at high magnification. Aways keep a dust cap on your telescope to keep the lens or mirror clean- except when you are using it! Your need a sturdy tripod or pedestal for your telescope. Set it up on a level, firm surface. New Moon is on October 15; watch for the crescent in the west after sunset following that date. The bright planet Jupiter may be seen low in the northeast in late evening. Venus is prominent in the east during morning twilight. Notes may be sent to firstname.lastname@example.org. Please mention where you read this column. Keep looking up!
Telescopes take you deeper