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A S T R O N O T E S ISSN 0048-8682
The Newsletter Magazine of the Ottawa Centre of the RASC
Vol. 23, No. 5 $5.00 a year May 1984
Editor.......Rolf Meier......4-A Arnold Dr.......820-5784
Addresses....Art Fraser......92 Lillico Dr.......737-4110
Circulation...Robin Molson....2029 Garfield Ave...225-3082
OBSERVER'S GROUP MEETING - APRIL 6 Dave Lauzon
President Peter MacKinnon opened the meeting at 8:20 pm with 48 people in attendance, of which 35 were members. Peter introduced our chairman, Gary Susick, who discussed the upcoming solar eclipse, and Astronomy Day, to be held May 5.
Gary introduced Rolf Meier with his feature presentation on his search for supernovae. Rolf began by showing the differences between novae and supernovae, and how each is formed. He then continued by showing the two types of supernovae, determined by their light curves. Some of the parameters involved in each light curve depend on mass, absolute magnitude, what type of galaxy each is found in, and the types of stars involved.
The result of a supernova is a large energy output. What is left behind is usually a neutron star or a pulsar, and if massive enough, it has been proposed that a black hole may form.
With supernovae exploding 2 to 3 times per century per galaxy, Rolf set out to observe 57 galaxies visually. He took pictures through the 16-inch telescope at IRO on Tri-x film, enlarged them to a size similar to how they would be seen through the eyepiece, and used them as an index. If a bright star was found visually and not on the charts or photographs, this would probably be a supernova.
Although Rolf made 155 observations last year without a single find, he stated that even this wasn't long enough.
Rolfs talk ended in discussion and a slide show showing the remnants of novae and supernovae along with various galaxies.
Gary Susick was up again and pointed out highlights of 1983. Some of these highlights included the surprise Comet IRAS-Araki-Alcock, the General Assembly in Quebec City with F. Roy and J. Hayes winning an award, Stellafane, with members winning awards there too, the October Deep Sky Weekend, Sandy Thuesen finishing her 10-inch Dobsonian, and the November Annual Dinner Meeting. At this meeting Sandy won the Observer-of-the-Year Award, and Robin Molson won the Merit Award. Frank Roy's big project of the year was to redesign the digital clock at IRO. In January, 1984, the library was dedicated to Stan Mott, and was renamed the "Stan Mott Library".
After a recap of last year, Gary introduced all of the coordinators, who gave a brief talk in their field. First up was meteor coordinator David Lauzon, talking about meteor showers of last year and this year. Many projects are planned for this year, and as those stated on page 4 of the March 1984 issue of Astronotes.
Next up was Linda Warren, our solar coordinator. She made 97 observations last year, and she showed members pictures of aurora and sunspots. The instrument which she uses is a 6-inch telescope with a full-aperture solar filter.
Instrumentation coordinator Malcolm Lambourne didn't show up, but Gary filled in for him. The instrumentation workshops will continue this year, along with the RASC public star nights.
Variable star coordinator Sandy Thuesen introduced a concept of a beginner's package for variables, for people without telescopes but with binoculars. She also would like to see a beginner's night for variable star observing. Near the end of the year, the Variable Star Award will be given to the observer with the best data.
Comet and Nova coordinator Dave Fedosiewich gave an update on comets of the past, present and future. He made the observation that, as the public becomes more aware of comets (ie, Halley's Comet), the interest in amateur astronomy rises. With this, he concluded that the information service of comet charts will have to be improved so that the public can be further informed. Following Dave's talk, Rolf Meier showed slides of Comet Austin and Comet IRAS-Araki-Alcock.
Occultation coordinator Brian Burke reminisced over past grazes. Upcoming grazes occur on April 18 and May 6. Details may be found on pages 8 and 9 of the April issue of Astronotes.
Radio coordinator Frank Roy discussed his project of upgrading the radio telescope. He also showed slides of the data from the radio telescope on Cygnus A and Cass A.
Lunar and Planetary coordinator Rolf Meier showed slides of past oppositions of Mars, and the other planets also. One particular slide showed the January configuration of the planets.
Deep Sky coordinator Gary Susick enlightened members with a slide show of celestial wonders.
Pete MacKinnon closed the meeting at 10:50, when members and guests were invited for refreshments.
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CORRECTION Dave Lauzon
In last month's Astronotes I wrote an article entitled "How Old Is This Rock Called Earth". On page 6 I stated that the oldest rocks found were in the Canadian Shield. This is not true. The oldest rocks were found in Isira, West Greenland, at 3800 million years.
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Here are the answers to last month's quiz:
1) William Herschel
2) Caroline Herschel
4) Adams and Leverrier
9) the Chinese
and 10 more questions:
1) What does "nebula" mean?
2) What is the most massive pair of stars in our galaxy?
3) What has the famous Variable Nebula?
4) What are shower meteors made of?
5) What type of galaxy is round?
6) How many observations are needed to measure parallax?
7) What are the Hyades?
8) In what constellation is M 107?
9) What is the Saturn Nebula?
10) How many constellations are there?
ANNULAR ECLIPSE OF THE SUN
On May 30, 1984, we will be fortunate (hopefully) to view an annular eclipse of the sun. The annular path will be visible in an area extending from the Pacific Ocean through central Mexico, and the southeastern United States, across the North Atlantic, terminating in North Africa. The central path, however, is very narrow, being less than 5 km wide.
One of the best cities to view the eclipse from, and where the AAVSO, Rolf, Sandy, and I will be going is Petersburg, Virginia. The last time an eclipse path fell within a populated region of the U.S. was in February, 1979. The next eclipse will be on May 10, 1994! So you
must do your best to get to Petersburg, Virginia. See the map below.
The maximum eclipse at Petersburg is to occur at 16:43 U.T. (12:43 E.D.T.). Astronomy magazine (May 1984) provides the path events from start to finish of the eclipse. The Diamond Necklace effect is one of the main events that observers will be looking for. In Virginia, the suns limb will exceed the moons mean limb by 1.8 arc-seconds. Where a lunar mountain extends beyond the suns limb, the annulus or "ring" will be broken. This makes the eclipse unusual in the sense that it is not total nor is it entirely annular. Opposite you will find 3 figures which clearly define the difference between annular, total, and partial eclipses.
In figure i, you can see that the dark conical shadow of the moon is not long enough to reach the earth, therefore the observer can see a ring around the sun. In figure ii, the shadow touches the earths surface, causing a total eclipse. The corona will be visible in this cone at totality. In figure iii, the axis of the shadow cone misses the earth entirely, so the eclipse is partial.
While observing, you must at all times be most careful to avoid looking directly at the sun - although tempting - it is equally devastating in its damage caused to the eye, as in any other eclipse! Using a full-aperture filter or projection is always safest. Welders glass #14 is another safe observing method. For observing beads of sunlight at the limb during annularity, glass #13 is safe, but once the event is over you should go back to #14 glass.
As the moon approaches the suns disk, it would be interesting to watch the ground under trees and bushes for little crescent-shaped images cast by natural pinholes (overlapping leaves) which will show the current phase of the eclipse. Familiar objects will appear astigmatic as the sun becomes misshapen. The dimming of the sun may cause unusual behaviour in birds, animals, and insects. Temperature may drop 10° or more.
Another phenomenon to watch for is shadow bands. They often appear as elongated patches or mottled, irregular patterns, bands or blotches of light and shadow from 1/2 inch to several inches in width. They sometimes move perpendicular to their length at a speed of several feet per second. They are visible for several seconds to several minutes before and after totality, longer at partial or annular eclipses. This will be something to pay attention to. It is not certain what causes this, but it is related to atmospheric disturbances.
The main feature to observe will probably be "Baily's Beads". These are a result of sunlight appearing through valleys on the eastern limb of the advancing moon, just as total eclipse begins, and then at the western end where it ends. The beads should also be seen at the northern and southern limb of the moon as well, depending on where you are observing along the path. It was during an annular eclipse that Francis Baily first observed the beads, on May 15, 1836. They are unpredictable, and it must be clear and cloud free.
Sometimes it is possible to see the corona during an annular eclipse, but if the ring of sunlight is very bright, it could be difficult. Venus, at magnitude -3.4 and 4° west of the sun, should also be observable.
This being my first solar eclipse, I am quite excited and hope that the day will be clear, and Murphy has a day off!
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LEARN MORE ABOUT COMETS HERE! Dave Fedosiewich
Part 2 - Some Famous Comets
By far the most well-known comet and most-observed comet of the last few centuries is Halley's Comet, which, by the way, is scheduled to return in late 1985.
The story of Halley's Comet has its beginnings in the late seventeenth century, at about the same time Isaac Newton was applying his ideas about gravity to astronomical bodies. Edmund Halley, the first to publish a telescopic atlas of the southern skies ( Catalogus Stellarum Australium ) had returned to England. Halley had always been interested in comets, and after the apparition of the great comet of 1682, decided to try and fit its path in the sky to a parabolic orbit, as he had obtained postions for this comet with great care.
During the same time, Halley had published a catalog of cometary orbits for 24 other well-observed comet apparations entitled Synopsis Astronomie Cometicae. He was excited to find that instead of parabolic orbits, he was able to identify some elliptical ones. In particular, he
found the Great Comet of 1682 to be moving in an elliptical path of high eccentricity and only a little inclination to the ecliptic.
Checking through the orbital characteristics of other comets on his list, he was struck by the similarity of the 1682 comet with comets which had appeared in 1531 and 1607. Halley was able to explain the difference in intervals on the gravitational attractions of Jupiter and Saturn on the comet. As a consequence, he was able to calculate that the same comet would reappear in 1758. Unfortunately, Halley died in 1742. When his Astronomical Tables was reproduced in 1749, it contained Halleys statement that the comet would reappear in 1758.
The great French comet hunter, Messier, began searching for it in the middle of 1758. The actual recovery went to a self-taught amateur astronomer, a Saxon peasant-farmer called Palitzsch, who with his home-made 7-foot reflecting telescope observed it on Christmas day, 1758.
The comet was due again in 1835, which was in fact a very suitable passage. In October of that year, the tail grew to 30° in length. The 1910 apparition of Halley's Comet was less spectacular, with a maximum brightness of 2nd magnitude. Contrast this with the passage of Comet IRAS-Araki-Alcock, which reached a brightness of 1st magnitude. Halleys Comet is expected to reach 5th or 6th magnitude in 1986, a far cry from earlier visits.
Apart from these descriptions of Halleys Comet, probably the most reliable record of a truly spectacular comet came as the Great Comet of 1264, which displayed a tail of more than 100° in length. Observers reported that when the comets head was just above the eastern horizon, the tail stretched westward past the zenith. It remained visible to the naked eye for over 4 months and was widely observed in China and Europe. Remarkably, both sets of observations agree quite closely, apart from the semi-hysterical overtones in European accounts.
The Great Comet of 1680, discovered by Godfrey Kick at Coburg, Saxony, became an eyecatcher with a tail almost 40° long. Edmund Halley also investigated this comet and he concluded that it was identical with a comet seen in 1106. We now know that he was probably wrong, since this comet is probably identical with the sungrazer 1843 I.
During the seventeenth century, the most remarkable comet after Halleys was the Great Comet discovered by Klinkenburg in Haarlem on December 9, 1743, with an independent discovery by De Chesaus in Lausanne on December 13. Its head became as bright as Venus, but the most outstanding feature was the array of multiple tails of which 6 divisions were clearly visible spread out like the fan of a peacocks tail, and a total of 11 separate tails were counted in all. This comet was bright enough to be observed with a telescope in broad daylight.
What follows is a short list of the more spectacular comets of the 19th and 20th centuries with a brief description.
Comet 1811 I - discovered by Flaugergues of Vivires near Monteliner - became a circumpolar object in the northern skies - widely observed throughout Europe.
Comet 1843 I - belongs to the sungrazer comet group - independently discovered by many observers - brightest at magnitude -6 to -8 only 4° from the sun's edge - tail 70° long.
Comet 1858 II - discovered by Donati of Florence - 3 well-developed tails - occulted Arcturus on October 5 of that year.
Comet 1861 II - discovered by Australian sheep farmer John Tebutt - the earth passed through the comet's tail at a distance of about two-thirds its length from the nucleus.
Comet 1874 I - discovered by Jerome Eugene Coggia at Marseilles - tail grew to over 40° in length - mostly a southern hemisphere object.
Comet 1907 IV - discovered by Daniel at Princeton, USA - many photographs were taken which show tail oscillations with a period of 16 hours.
Comet 1910 I - first spotted by diamond miners in South Africa - maximum tail length about 40° - the comet took on a yellowish light due to the bright sodium emissions in the tail.
Comet 1914 V - discovered by Delavan at La Plata in Argentina - cosmic portender to World War I.
During the 1920's and 1930's, there was a drought of really spectacular comets. In 1943, Comet Whipple-Teozadze was discovered but was not as bright as most great comets of the 19th century.
Comet 1947 XII - discovered independently by many observers in the southern hemisphere including the deck-watcher of a British naval vessel cruising in the South Atlantic - orange colour due to very strong sodium emissions.
Comet Arend-Roland - discovered in 1956 - brilliant naked-eye object in the northern skies - tail over 30° long - sunward tail spike.
Comet Mrkos - discovered in 1957 at the Skalnate Pleso Obseratory - independently discovered with the naked eye by many other observers in the northern hemisphere, including a British schoolboy.
Comet 1961 V - first spotted by a South African Airways stewardess - was bright for only a short time.
Comet 1965 VIII - famous Ikeya-Seki sungrazer mistaken by professor Bart Bok for a brilliant searchlight beam - disrupted into 2 separate nuclear regions minutes before perihelion.
Comet 1967f - first spotted by Herbert E. Mitchell in Queensland, Australia - mostly a southern object - strong greenish light emitted by the tail.
Comet 1969i - discovered by John C. Bennet in South Africa - became a 0 magnitude object towards the end of March, 1970.
Comet 1975h - most recent Comet West - visible to the naked eye even near large cities - comet split 3 times to consist eventually of 4 distinct nuclear regions (this event was independently discovered by Ottawa Centre members at North Mountain Observatory) - fan-like tail.
Next month, the orbits of comets.
* * *
SEMI-REGULAR VARIABLES Sandy Thuesen
In 1796, Sir William Herschel (of Uranus fame) began studying the third-magnitude star Alpha Herculis, which varies between magnitude 3.0 and 4.0 in an irregular manner. His son, John Herschel, continuing his father's work, drew attention to several similar stars which, unlike other variables, such as Cepheids, eclipsing binaries, and even long-period variables, appeared to have no obvious pattern to their light change. Not until the end of the 19th century, after a great amount of observational material became available, was it possible to show that although there exist some stars for which no trace of periodicity whatever can be found - these being true irregular variables - in several, a certain amount of periodicity can be found, and these are classed as semi-regular variables.
Like long-period variables, theses stars are mainly red giants or supergiants. Their amplitudes are smaller than those of the Mira-type variables, rarely exceeding two magnitudes. Semi-regular variables are divided into four sub-classes:
SRa - Giant, late-spectra (M, N, or S) stars, with light curves often similar to LPVs. They can be differentiated from LPV's by their smaller light range. Examples: S Aql and R Uma.
SRb - These stars exhibit a generally recognizable periodicity, but at times this is replaced by more irregular variations or even periods of constant brightness. Example: U Boo.
SRc - A fairly large group of supergiants of late spectral classes with light changes of the order of a single magnitude. Examples: Alpha Herculis, Alpha Orionis.
SRd - A small group of giants and supergiants, with earlier spectra than the preceding class - usually between types F and K. Many have light curves like RV Tauri variables, with alternate deep and shallow minima.
* * *
VARIABLE STARS OF THE MONTH - (30) HER AND X HER
by Sandy Thuesen
This month Astronotes features two semi-regular stars, both in the constellation Hercules, which is well up in the east during evening hours. Both are red stars, and therefore the quick-glance method of making estimates should be used. Both are binocular variables.
(30) Her - An easily-found star near Sigma Her, with an average period of 80 days and a variation in magnitude of about 1.5
X Her - This one takes a bit more time to pinpoint, but is easily found with a bit of star-hopping. X has a period of approximately 100 days and a variation of about 1 magnitude.
A finder chart is opposite for identification and location of these stars and charts with comparison magnitudes are available from me at any Observer's Group meeting. Please feel free to give me a call at 829-7514 if you experience difficulty in observing any variables or need information of any kind.
* * *
g (30) HERCULIS
Position: (1950) R.A. 16h 27 m; Dec. 41° 59m Period: 80 days (average)
Magnitude: 4.4 - 6.0
Position: (2000) R.A. 16h 02m; Dec. 47° 14m Period: 100 days (average)
Magnitude: 6.3 - 7.4
MARS COMES TO OPPOSITION
This is the month that planetary observers have been waiting for, when the planet Mars comes to a favourable opposition. The date for this is May 11, although May 19 is significant in being the date of closest approach. Around this period of time, the apparent diameter of Mars will be up to 17.6 arc-seconds, not quite the maximum possible of 25 arc-seconds, but still big enough to pick out a lot of features. This is comparable to the diameter of the ball of Saturn, which also comes to opposition this month, on the 3rd, with an equatorial diameter of 18.7 arc-seconds.
Over the past few months I have been watching Mars grow in apparent diameter, and with this growth I have seen more and more features. At first, as Mars came out of the morning twilight, he was still quite small and featureless, but with an apparent phase. A polar cap and a hint of dark patches was all that was to be seen. Now, the phase is nearly absent. Features are easier to see, and are now identifiable with features on an albedo map.
If you are a newcomer to planetary observing, here are a few pointers. The features that can be seen through an amateur telescope of 6 inches or so are fairly detailed, but only under steady seeing conditions. Typically, when you first look at Mars, you will see a blurry orange disk. This is due to several things; turbulent air, a scope not at thermal equilibrium or in poor alignment, poor focus, but mostly the blur is due to a lack of familiarity with the object. Take time and care to focus properly, make sure the scope is in good alignment, and that the optics are good. Now look and wait. Your eye-brain system will begin to analyse the blurry messages. Hints of features appear as the brain struggles to understand this new data. And suddenly, the air becomes rock-steady! For one brief instant the planet is crystal-clear, and a myriad of shapes are seen. But the good seeing vanishes, and a fuzz is all you see. And so it is. Moments of good seeing can be rare, and must be awaited. So look for many minutes before you give up. A half-hour of observing will bring to view many fine details. You will be anxious to record your views, probably by making a pencil drawing. Photography is very difficult, but is worth trying. For visual observing, a power of 150 or so is required, and higher if the seeing permits. I would be happy to hear about your observations either at a meeting or on these pages.
The Okanagan Astronomical Society invites you to attend the Mt. Kobau Star Party this August 23 - 27, during new moon. Mt. Kobau offers fine, dark skies in the dry B.C. Interior. Twenty years ago it was selected as the site for a 4-metre telescope. The telescope was unfortunately never built, but there is still an all-weather road to the observatory's intended location at 6107 feet. This is where the star party will be held. While we cannot offer a 4-metre instrument, there will be a 0.5 metre (the Victoria RASC Centre's 20"). OAS members are bringing 17.5" and 13.1" Dobsonians and other large telescopes are expected. We hope your telescope will be there as well, whatever its aperture. The outstanding opportunities afforded by this combination of large instruments and an excellent dark sky will be protected by a complete ban of all lights during the six hours of darkness, except for dim red flashlights.
The Mt. Kobau Star Party will include a telescope making competition (the chief judge will be Mr. Leo Vander Byl of Victoria); an astro photography competition judged by Mr. Jack Newton, also of Victoria; a Saturday swap table; and special twilight talks by Mr. Newton and Dr. Tom Landecker, an astronomer at the Dominion Radio Astrophysical Observatory (DRAO). There will be time available for you to speak on Thursday and Sunday evenings. All of these events will take place on the mountain between 6 P.M. and 9:45 P.M. Tours of DRAO will be given Sunday from 2 to 5 P.M.
The summit offers only very spartan facilities. There will be electrical power, a large awning for shelter, and privies. There is no water - you must carry your own. Thus accommodation will be in the resort village of Osoyoos, 17 miles away and a mile lower in altitude. There are numerous campgrounds and motels along the warm waters of Osoyoos Lake to choose from. In addition to the beaches on its chain of lakes, the Okanagan Valley offers scenic drives and many tourist attractions.
There is a locked gate at the bottom of the Mt. Kobau access road. Because of the cost of manning the gate, the mountain will be closed between 5 A.M. and 5:30 P.M, However, if you observe until dawn you can sleep on the summit until noon and the gate will bo opened briefly at 1 P.M. A responsible person will remain on the summit through the day to ensure that telescopes there are not tampered with.
Commercial exhibitors are welcome and encouraged but will have to provide their own exhibit space such as a van, motorhome, or tent.
Please register early if possible, so that we know how many to plan for. The registration fee is $18 for one person, $35 for two, and $40 for a family. Detailed brochures on the star party and accommodations in Osoyoos will be sent to registrants in early May.
Detach this form and mail it to: Mrs. Jackie Warrington, Site 16 Comp 30, RR# 1,
Winfield, British Columbia V0H 2C0
Your name and address:
Days you will attend: Thurs. 23rd ___, Fri. 24th ___, Sat, 25th ___, Sun, 26th
Mon. 27th . Can you help clean up Monday? ___
Please describe any telescopes you are bringing. _____________________________
Are you entering the telescope making contest? _____ Astrophotography contest?
Are you interested in being a speaker? ___ If yes, Thurs. or Sun? ____
Will you tour DRAO Sunday? ___ Will you be a commercial exhibitor? ___
Do you wish to buy a M.K.S.P. T-shirt ($9 each)? What size and gender? _______
Amount registration fees enclosed; $______ For how many people? ____