SKY REPORTER: Telescopes Great and Small

During the past century three leaps in telescope development enabled spectacular advances in our knowledge of the universe. Dedicated in 1917, the 100-inch Hooker reflector on Mt. Wilson provided Edwin Hubble with detailed correlations between remote galaxy distances and their rates of movement away from us, revealing the universe’s expanding nature. 

The next major jump in telescopic light gathering ability came in 1948 with the 200-inch Hale telescope, the “Giant Eye of Palomar.” It provided a four times increase in light grasp over the 100 inch and served a remarkable tenure as the world’s largest. Since then there have been incremental increases in telescope sizes and currently there are several instruments in the range of about nine to ten meter diameter, each with light gathering ability around four times that of the venerable 200-inch.

With its primary mirror a relatively modest 2.4 meter (94.5 inches) in diameter, the Hubble Space Telescope nevertheless operates in the pristine environment of Earth orbit, free from corrupting effects of starlight twinkle that previously plagued ground based observatories. Hubble has explored marvelous new vistas including helping determine the age of the universe as well as aspects of dark matter and dark energy. Later this decade Hubble will be succeeded by the James Webb Space Telescope, with a primary mirror of 6.5 meters, gathering over seven times the light of its famous space predecessor. Unlike Hubble, the Webb telescope will orbit the Sun rather than Earth and concentrate its gaze on the infrared rather than visual parts of the spectrum.

Even as Webb is being constructed to up the ante in space telescope size, revolutionary technological advances now allow ground based telescopes to significantly mitigate atmospheric distortions that have limited the viewing clarity of such instruments since the time of Galileo. A new generation of Earth bound telescopesis planned, each with an array of cooperating mirror components dwarfing light grasps of their remarkable 20^th century predecessors.These colossal ventures include the 24.5-meter Giant Magellan Telescope planned for Las Campanas Observatory in Chile; the Thirty Meter Telescope to be built on Mauna Kea in Hawaii; and the European Extremely Large Telescope with a 39 meter diameter at Cerro Armazones Observatory, Chile. 

While we look forward to magnificent discoveries from these endeavors, we can savor present telescopic vistas closer to home. When thinking about getting a telescope for yourself or perhaps for a gift, before doing so I strongly recommend binoculars and a good sky field guide. These will help you personally become familiar finding your way around the night sky and identifying bright stars, planets, and aspects of changing lunar phases. By doing so over a period of months, your ability to enjoy a new telescope will be greatly enhanced. 

I also recommend that you make use of many telescope observing opportunities provided by local astronomy organizations including the Amateur Astronomers Association of New York. Members regularly bring varied types of substantial telescopes to sites for free public viewing, and they’re usually glad to discuss features of their devices. And, if you’ve never had the pleasure of seeing objects through an observatory telescope, here are some in our area open to the public on scheduled evenings throughout the year:

• McDowell Observatory at the Meadowlands Environment Center
• Sperry Observatory at Union County College, Cranford NJ
• Stamford Observatory at Stamford Nature Center and Museum
• Paul Robinson Observatory, Voorhess State Park, NJ
• United Astronomy Clubs of NJ observatory at Jenny Jump State Forest
• Custer Institute and Observatory, Southold Long Island

The Moon

Planets

At 8 pm Thursday July 3rd, Earth was at aphelion, its furthest distance from the Sun, a range of about 94,506,000 miles.

Early risers on the morning of July 24 may look low in the east-northeast at about five a.m. and see a beautiful assembly of ever brilliant Venus six degrees to the left of the waning crescent Moon, and about eight degrees to the upper right of Mercury.