Home > Astronomical History, Ephemeris Program, Telescopes > 05/29/2015 – Ephemeris completes 40 years on the air

05/29/2015 – Ephemeris completes 40 years on the air

May 29, 2015

Ephemeris for Monday, June 1st.  Today the Sun will be up for 15 hours and 20 minutes, setting at 9:21.   The Moon, 1 day before full, will set at 6:17 tomorrow morning and tomorrow the Sun will rise at 6:00.

We’ll start Ephemeris’ 41st orbit of the Sun by looking at the skies of June.  There’ will be a lot of sun in June and very little night.  The daylight hours will increase a bit from 15 hours and 20 minutes today to 15 hours and 34 minutes on the 21st, retreating back to 15 hours 31 minutes at month’s end.  At this time of the year the sunset times for Ludington, Interlochen, Petoskey and Mackinaw City are very nearly the same.  However the sunrise times are at their most divergent.  With Ludington’s sunrise being 14 minutes later than Mackinaw City’s.  The altitude of the sun above the southern horizon at local noon will hover around 68 to 69 degrees.  Local noon, when the sun is actually due south will occur at about 1:43 p.m.  Here’s what we’ve been waiting for:  Summer will start on the 21st at 12:38 p.m.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.


This is my article in the June Stellar Sentinel, the monthly newsletter of the Grand Traverse Astronomical Society

At the end of May I will have completed 40 years of the short program on Interlochen Public Radio (IPR) I call Ephemeris. The first airing was June 1st 1975. It currently airs twice each week day at 6:49 a.m.** on their news stations, and at 6:59 a.m.** on their classical music stations. This article isn’t about Ephemeris, but what has transpired in the last 40 years. It’s kind of sobering to realize that 40 years is approximately 10% of the span of 406 years since Galileo first turned his crude telescope to the night sky. Over the next year I’ll look at what has been happening in astronomy and space in those 40 years. This time I’ll look at some telescope advances in that time.

In 1975 the largest optical telescope in the world was the Hale 200 inch (5 meter) telescope* on Mount Palomar, today the Keck I telescope and its twin Keck II on Mauna Kea in Hawai’i are among the largest in the world with 10 meter diameter mirrors. Keck I saw first light in 1990, while Keck II saw its first light in 1996. They share the peak with two 8 meter telescopes: Gemini North and Subaru, among other large scopes. The Thirty Meter Telescope (TMT) is about to be built up there pending the clearing up of a dispute with native Hawaiians who consider the mountain sacred.

Actually the Kecks have been edged out by the Gran Telescopio Canarias, in the Canary Islands with a 10.4 meter mirror, which saw first light a few years ago. Not to be outdone, the European Southern Observatory, a consortium of 13 European nations have established a beachhead in the Chilean Andes and are building the European Extremely Large Telescope (E-ELT). Its segmented mirror will span 39.3 meters (1,550 inches), nearly eight times the diameter of the Hale telescope, and is expected to see first light in 2024. If Ephemeris and I will be around another 10 years, we’ll see that too.

Many of the existing large telescopes have been shown up by NASA’s most popular satellite, the Hubble Space Telescope (HST) which has only a 2.4 meter (94.5 inch) mirror. Telescope placement is like real estate: Location, location, location. The higher the better to beat the bane of telescope viewing atmospheric turbulence. Nearly 400 miles altitude in orbit solves that problem nicely. The next generation space telescope is to be launched in three years. It’s the James Webb Space Telescope (JWST), named for an Apollo era NASA administrator. It will be launched by an ESA Ariane 5 rocket to the Earth-Sun L2 point a million miles opposite the direction of the Sun. It will operate in the infrared.

Not to be outdone by Hubble, ground based astronomers have found a way to combat atmospheric turbulence, or “bad seeing” as we term it: It’s called adaptive optics. Ever see those time-lapse videos of the Keck and other observatories shine lasers skyward. These are tuned to the wavelength that excites sodium atoms in the atmosphere above 50 kilometers to produce an artificial star. By deforming the telescope mirror or mirror segments to straighten out the artificial star’s light the atmospheric seeing can be improved by a factor of 16 or better. This technique works better in the infrared whose wavelengths are longer than visible light.

Our atmosphere is relatively transparent at wavelengths that happen to be at the Sun’s peak output. That is where evolution has given us the ability to see in. However to use an acoustic analogy, we are doomed to hear the cosmic symphony by listening to a single octave on a piano that stretches in a mile in either direction from middle C.

In 1975 radio astronomy was beginning to work with multiple telescopes to produce radio interferometers that spanned the continent to produce the effect of a single telescope of the width of the array of many telescopes. These arrays have now spanned oceans, and even into space. These interferometers rival and surpass the resolution of optical telescopes. A prime goal is to resolve the black hole in the center of the Milky Way, something that can’t be seen invisible light, which can’t penetrate the gas and dust along the 26,000 light year path to the center of our galaxy.

Today there are neutrino telescopes underground, X-ray telescopes and Gamma Ray telescopes orbiting the Earth, an armada of spacecraft orbiting and studying the Sun. Also techniques and instruments have been refined, so that when once the idea of detecting planets around other stars was thought to be a dream for the future, we’ve been discovering them by the thousands over the last 20 years. Even amateur astronomers can do it now.

In the 45 seconds I have to devote to astronomical topics after the sunrise, sunset and lunar phase information in an Ephemeris program I cannot delve deeply into the wonders that modern astronomy brings. But I can give a taste, and provide the key to the heavens to just go out and experience the wonder of the universe that is the night sky as seen from our own back yards.

* I forgot about BTA-6 in the Caucasus Mountains in the then Soviet Union, a 6 meter telescope that saw first light in late 1975, so I guess I was still correct on the Ephemeris launch date.  It has a history of problems and was never really able to fulfill its promise for a number of reasons.  It beat out the Hale telescope by 38 inches.  It did pioneer the alt-azimuth mount that all large telescopes now use.

** Correction (June 4):  These are the corrected times.  I was an hour too late.   Thanx and a tip of the old observers cap to Emmett Holmes for the heads up.

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