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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. 3 $5.00 a year March 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 - FEBRUARY 3 Dave Fedosiewich
Chairman Gary Susick opened the meeting at 8:20 pm with 34 people in attendance. Gary forwarded information concerning RASC memberships, as well as a brief description of the centre's two observing sites.
Vice-chairman Malcolm Lambourne introduced Brian Burke as the first speaker, who informed the group of upcoming occultations for 1984. More information will be passed on as the events approach.
Next up was yours truly with some good news and some bad news about Comet Crommelin. The good news is that this comet was expected to be bright. The bad news is that the comet, reported by Rolf Meier, was not so bright as expected. See the article elsewhere in this issue for more information.
Variable star coordinator Sandy Thuesen gave the group a quick description of the 3 variable stars she requests that observers watch this spring. She made a request for lots of observations so that a comparison of magnitude estimates could be attempted.
Rolf Meier, our planetary coordinator, compared slides of the planetary alignment taken both in Ottawa and Tucson, Arizona. Rolf explained the difference in angle of the alignment as viewed from the two locations. Also out, but not in Canada, is a new high-speed 3M film.
Linda Warren then gave a complete account of her and Rolf's stay in Arizona in late December and early January. Some interesting slides depicted local foliage and animal life. Of particular interest was the abundance of ghost towns in the area. Boo!
Gary Susick was up last with further photos of the planetary alignment in January.
The meeting was adjourned at 9:35 pm.
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COUNCIL MEETING - JANUARY 25 Rob McCallum
The primary purpose of the January Council meeting was to appoint the various committees for the coming year. The committees and their members will be reported in Astronotes once they are finalized. The annual report of the centre was also read and approved.
The treasurer summarized the financial situation. Efforts to keep costs down continue to keep our position satisfactory. The slide in membership over the past few years appears to have reversed as numbers are up over last year's total at this time.
The observatory was reported to have the access road blocked with snow since early December. Plowing was indicated to be expensive and futile, and hence members visiting IRO are advised to do so on skis or snowshoes.
The dinner committee presented a report on last November's dinner. Fewer tickets were sold than were expected, and since the caterer had a minimum number of meals for the meal selected, a larger than expected deficit was incurred. As a number of members appeared to not have attended due to the ticket price, efforts will be made to find a cheaper location without sacrificing the meal quality for the 1984 dinner.
The possibility of sending a questionnaire to the centre members was discussed. It was felt that it would help in planning activities, attracting volunteers, finding out how members first found out about the RASC, and so on. Council directed the Activities and Facilities committee to prepare a draft questionnaire for consideration at the next council meeting.
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COORDINATOR'S MEETING - FEBRUARY 3 Gary Susick
The first coordinator's meeting was held right after the February Observers Group meeting on Friday, February 3. All coordinators were present with the exception of Dave Lauzon and Bill Donaldson.
The main goal of the meeting was to devise an exciting and enjoyable observing program for 1984. Participation, the backbone of all good observing programs, will be strongly emphasized and promoted. Through a cooperative effort, the proposed observing program will make 1984 a successful year.
Each coordinator and his or her 1984 observing program is listed below.
Dave Fedosiewich - Comets and Novae
-a series of 9 articles for Astronotes
-distribution of comet-observing forms
-historical background of comet observing
-the chain of events in reporting and confirming a possible comet discovery
-Halley's Comet update
-comet ephemeris on periodic and new comets
Brian Burke - Occultations
-presentations of grazing occultation predictions
-required preparations and equipment
Linda Warren - Solar and Aurora
-recording and reporting sunspots
-annular eclipse projects
-equipment requirements, filters and telescopes
Rolf Meier - Lunar and Planetary
-encourage drawing and photography
-viewing of Jupiter's Red Spot
-visual challenge - determine the earliest visible crescent moon after new moon
Malcolm Lambourne - Instrumentation
-Tuesday night instrument workshops
-potential projects - mirror grinding, camera adapters,
slide observing focuser
-June instrument night
-sidereal clock modifications
- Astronotes articles
Sandy Thuesen - Variable Stars
-equipment requirements - binoculars, telescopes
-distribution of variable star finder charts
-articles, charts for Astronotes
-how to determine magnitudes
-selected variable stars used for the Variable Star Award
-photometry - possible utilization and technique
-observing sessions at Quiet Site, IRO, and Star Nights
Gary Susick - Deep Sky
-Messier finder charts in Astronotes
-observing equipment and techniques, setting circles, star hopping
-Messier Marathon in April
-log book requirements
Frank Roy - Radio Astronomy
-radio telescope modifications
-interpretation of data
David Lauzon - Meteors
-Quiet Site observing program
-monthly meteor update
-technique and methods of meteor observing
-determination of meteor altitude
-correlation of visual meteor reports and CHU recordings
-meteor observing forms
Several concepts that were popular over the last few years will continue to be promoted. Regional Star Nights, IRO and Quiet Site star nights, and the Deep Sky Weekend will provide foundations to encourage participation as well as public awareness of our activities. The Constellation of the Month will be presented and revised. It will provide a format for the presentations of the various coordinators.
I would like to thank Linda Warren for taking the notes at the coordinator's meeting.
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TELESCOPE WORKSHOP Malcolm Lambourne
A reminder - the Telescope and Instrumentation Workshop still operates, every Tuesday evening from 6:30 to 10:30 at 312 Woodroffe Avenue (across from Carlingwood Mall), and all members of the Ottawa Centre are invited to use its facilities. The purpose of the workshop is to provide help with ideas, design and construction of telescopes, accessories, or any kind of astronomical instrumentation. So dust off your half-completed projects and your half-baked ideas, and bring them along (but call first, 729-8112, to make sure I am available).
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ASSORTED BUSINESS Rob McCallum
During the annual phone-around before last November's dinner meeting, I discovered that we do not have phone numbers for quite a few members. As a result, these members were not phoned and at least one person consequently missed the dinner.
I would like to complete our address list as best I can before next years dinner, so if members have any doubt about whether we have your correct phone number, contact me and Ill check it out. My home phone number is 225-3167, or if you cant get me, see me at an Observers Group meeting.
* * *
The aurora borealis was imaged for the first time in full daylight by Air Force researchers recently, using an ultraviolet imager on the HILAT satellite. At this wavelength, the dayglow is faint and the aurora is bright.
A MARCH GRAZE
This year's grazing season commences on the evening of March 12, when a 7.9 magnitude star is grazed by the dark lunar limb. The graze site is about 7km southwest of North Gower, Ontario, not far from last September's graze. The details for this lunar grazing occultation are:
date: March 11
time: 20:50 EST
star: X 9363
limb: south, dark
moon: 64% sunlit
location: 7km southwest of North Gower, Ontario
Since the driving time will be approximately 40 minutes, we will meet at the Billings Bridge Shopping Centre outside the Mr. Donut at 18:30 and we will leave at 19:00. Although this will be a difficult graze to observe it should be interesting because the south limb has many high mountains. Telescopes, tape recorders, and radios that can receive the time signal are required. If you would like to get involved in this graze expedition or would be willing to lend some equipment, let me know at the meeting or call me at 521-8856.
TYPES OF VARIABLE STARS Sandy Thuesen
This month I will discuss two types of variables, the long-period variables, and the Cepheids.
Variable stars with cycles of 80 to 1000 days are known as long-period, or Mira-type variables, named for Omicron Ceti (Mira), the first long-period pulsating star discovered. These stars are the most numerous class of variable known to date, nearly 4000 having been catalogued.
Charactersistics of Mira-Type Stars
1) The light range is very great, usually 5 to 6 magnitudes, but a few stars exceed 9 magnitudes.
2) Periods range from about 60 days to 700 days, with a few stars exceeding these limits. Periods between 200 and 400 days are most common. Generally, it seems that the stars of longer period have a greater range and a deeper colour, but not necessarily a higher luminosity.
3) The variations do not repeat themselves with absolute regularity; there are often considerable changes from one cycle to the next, both in period and amplitude. It is impossible to predict the date or amplitude of any one maximum from those which have preceded it, and for this reason alone continous observation of these variables is of great importance.
4) Stars of this type are all red giants with absolute magnitudes (maximum) ranging from about -1 to -3. About 90% of these stars are spectral class M, with surface temperatures ranging from 2000° C to 3000° C, classes N and S claim about 5% each, and a very few belong to the rare class R.
The Cepheids are variables of much shorter duration
and with much more precise cycles. Stars of this class are
named for Delta Cephei (also mentioned in February
Astronotes ), the first example of this type of star to be discovered in 1784. Since the discovery of Delta Cephei, over 300 stars of this type have been found and they form one of the most interesting and important class of variables known.
Characteristics of Cepheids
1) Cepheids are all very luminous white and yellow giants of spectral classes F, G, and K.
2) These stars have periods of from a few hours up to
about 50 days (a typical period is from 5 to 8 days).
Cepheids of very short period (under a day) are classified as "cluster variables", from their abundance in globular clusters. These stars are smaller and less luminous than normal or "classical" Cepheids and their spectral types are A and F. A typical star of this class is RR Lyrae. A third sub-class of this type includes stars with extremely short cycles of less than a few hours and are known as "dwarf" Cepheids.
3) The period of a Cepheid is generally very regular and in many cases is known to a fraction of a second.
4) The light variation of a typical Cepheid averages less than one magnitude, although a few vary by up to 1.5 magnitudes.
5) The light curves of all Cepheids show a marked similarity in shape and amplitude. The rise to maximum is nearly always more rapid than the decline, with the ascending part smooth and steady and the decline often showing slight irregularities. A typical light curve appears below:
* * *
The last comet of 1983 was P/Clark, 1983w, which was recovered by J. Gibson at Palomar on December 15. The first comet of 1984 was Comet Bradfield, 1984a. It was at perihelion in late December and is now fading away from its current 13th magnitude.
VARIABLE STARS OF THE MONTH - RT AURIGAE AND T MONOCEROTIS
This month Astronotes features RT Aur and T Mon, two easy-to-find binocular variables - both Cepheids. These stars are well-placed in the evening sky and locating them should not be difficult as they are both situated near distinctive star groupings. Charts for these stars accompany this article. Magnitudes of nearby comparison stars have been included in these charts. However, if anyone wishes to obtain more detailed charts for these stars, I'll be happy to provide them.
RT Aur is located slightly less than midway along a line drawn from Epsilon Geminorum to Theta Auriage (you will have to look up Theta on a star map - it wont fit in this chart!). Its period is exactly 3.728261 days and it varies in brightness by about 1 magnitude. The rise to maximum requires about 1.5 days and the decline about 2.5 days.
T Mon is located between the Rosette Nebula and a string of 5th and 6th magnitude stars lying approximately halfway between Alpha Orion and the Rosette. It has a cycle of just over 27 days and varies in brightness by 1 magnitude.
Check these stars every clear night. After you have accumulated a number of estimates over a period of time, try plotting them on a graph, showing magnitude and period, and you will find them developing a light curve much the same as that shown here for Delta Cephei.
You may have noticed another variable lurking in the general area of Orion, while checking the chart for T Mon. May we introduce RX Leporis, a bright, easily-found binocular variable with an irregular cycle. RX is located in the constellation Lepus, not far from Beta Ori. It appears very close to Iota Leporis and is reddish in colour. Anyone wishing a detailed comparison chart for this star may obtain one from me at any Observers Group meeting, or by calling 829-7514, for mailing.
Good observing! I look forward to receiving any observations you make.
The charts for RT Aur and T Mon are on the following pages.
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THE 1984 QUADRANTIDS
Looking back through Astronotes, I came across the last write-up for observing the Quadrantids in Ottawa. In 1981 it was exceptionally clear. Peter Millman stated that he had not seen it that clear for a maximum shower in 20 years; it was also -35° C.
Ottawa, 1984, heralded the usual cloudy weather. Arizona, fortunately, was wonderfully, brilliantly clear. The temperature was an acceptable +5° C - no biting cold to cause discomfort - we were under prime conditions to observe this short-peak shower.
Astronomy magazine provided a short history of the shower as follows:
Joseph de Lalande, a French astronomer,"created" a new constellation, calling it Quadrans Muralis. (It was not explained why he decided to do this.) He chose stars from Hercules, Bootes, and Draco, and voila - The Mural Quadrant. Well, it didn't seem to catch on, but it was around long enough for the shower to acquire the name Quadrantids.
I looked at his area of the sky in Norton's just for fun, to make up what my version of the "mural" would be. You should try it!
The radiant of this shower at maximum is 15h 28m in RA and +50° in declination. The predicted hourly rate is 40 per observer, and a speed of encounter of 41 km/sec.
According to a number of sources, the shower was to peak at 10:00 UT, 12:00 UT, or 02:00 UT. Needless to say, we were delighted with the time frame we had and decided that whatever time we observed should be okay. We set the alarm for 3:30 am MST and official observing time started at 3:45, continuing until 5:45.
As you can see from my graph of data collected, we recorded at 10-minute intervals. Total number of meteors observed was 186, 136 being Quadrantids. Some of the meteors designated as being part of the shower were very fast. The speed was the only question of it being a Quadrantid, since they came from the right part of the sky.
You will note that one period was a little longer than the 10-minute interval. When I prepared my first graph, it was quite remarkable how it suddenly peaked at 5:45. Nonetheless, you can stll see a significant increase in non-shower meteors, which seems to support the theory that you will see the most meteors at around 6:00 am. Dave Lauzon gave a talk on this phenomenon at a recent meeting. But getting back to the period during which we observed longer, I averaged the data to give a more accurate picture.
What follows here is a summary of the rates of meteors observed for each observer:
observer meteors Quadrantids 10-min per.
Linda Warren 46 29 10
Rolf Meier 97 75 11
David Levy 48 36 11
Gerald Schieven 40 28 12
Forty-five of the total meteors were seen by 2 or more observers, and 32 of the Quadrantids were seen by 2 or more observers.
Data for the observing site is as follows:
site: Corona de Tucson, Arizona
Latitude 32°N, elevation 3000'
Linda Warren - facing east
Rolf Meier - south
David Levy - north
Gerald Schieven - west; also recording
weather: very clear and dark, limiting mag about 6.5
time: Mountain Standard Time (GMT minus 7 hours)
I'd like to take this opportunity to give my thanks again to David Levy for his kind hospitality, his eagerness to share his telescopes with us, and showing me some of the finest views I have ever seen through his 16-inch.
P/CROMMELIN - A DUD?
The expected magnitude for periodic comet Crommelin was to be about 12 for the beginning of the year. IAU reports told otherwise, with an estimate of 18.5 for January 1. Unfortunately, this information was passed on to me at the February meeting, so members may have been in the dark as to what has transpired since.
Rolf Meier reports that John Bortle observed the comet later in the month of January with the foilwing estimates: Jan 21, 11.5; Jan 26, 10.5. Hopefully, this is a sign of good things to come for P/Crommelin, which is expected to reach maximum brightness around the first few days of March. Any other reports of observations of this comet would be greatly appreciated. An ephemeris for the comet is as follows:
date RA Dec mag
March 1 1h 59.1m -3° 23' 7?
6 2 29.0 -5 40
11 2 59.8 -8 02 8?
16 3 31.5 -10 23
21 4 03.8 -12 36 9?
26 4 36.5 -14 34
31 5 09.1 -16 14 10?
The above coordinates are for epoch 2000.0, whereas the Handbook uses epoch 1950.0.
Also of interest this month is the return of P/Encke. An ephemeris for this comet is in the Observer's Handbook 1984. More information at the March meeting.
* * *
LEARN MORE ABOUT COMETS HERE! Dave Fedosiewich
This month, I begin the first in a 10-part series on everything you've ever wanted to know about comets but were too busy observing to ask. Topics will range from the origin of comets to comet hunting; from the study of cometary orbits to their physical makeup, and more. Perhaps readers of this series can suggest some topics not covered in this series, so I'll make things easier by listing what I intend to cover:
1. comets in history
2. some famous comets
3. the orbits of comets
4. the structure of comets
5. the physics of comets
6. comet hunting/discoveries
7. the comet hunters
8. observing comets
9. the origin of comets
10. comets and the origin of life on earth
part 1 - Comets in History
The word comet is derived from the Greek "komets" meaning "the hairy one". Since man first began observing the night sky, he was puzzled over the sudden appearance of bright comets. The ancient Chinese, who were excellent observers, compared comets to brooms in the sky when they wrote their chronicles.
In the Bible, there are only vague references to early comets, and probably the most prominent one is in 1 Chron 21:16:
"and David lifted up his eyes, and saw the angel of the Lord stand between the Earth and the Heaven, having drawn a sword in his hand stretched out over Jerusalem..."
Comets were certainly influential objects in the Greco-Roman world (Roman Empire). The writers of the day described comets as precursors of fatal events. The births and deaths of emperors were allegedly accompanied by brilliant comet apparitions, although there are no carefully-recorded events.
Democritus, whose name is certainly familiar with early atomic theory, strongly believed that all comets were the souls of famous people who, at death, were transported into the heavens as brilliant lights. The bright comet which appeared in 43 BC was supposed to be the soul of Julius Caesar transported to the heavens.
Even during this period in history, more sensible solutions to the comet mystery were proposed. Aristotle pronounced that, although comets were not true astronomical bodies, they inhabited the upper region of his three regions of air. Diogenes, Hippocrates, and several others of the Pythagorean school believed instead that comets were in common with the planets, which for them, wandered among the stars.
On the other hand, Pliny, who lived in the first century AD, wrote several passages about comets and terrible significance of their appearances. In the 4th and 5th centuries, in fact, this type of belief was so widespread that chronicles recorded comets which were actually never seen to mark the passing on of some powerful figure of those times.
The imagination of some people, as in this account of the comet of 1528, is highly representative of the ideas of the time. Writes the famous French surgeon Ambroise Pare:
"This comet was so horrible and so frightful and it produced such great terror ... that some died of fear and others fell sick."
When Halley's Comet appeared in 1456, the Pope Calixtus III, himself struck with general terror, ordered public prayers to be offered up for the deliverance from this comet and the enemies of Christianity.
Fortunately the Renaissance eventually began to influence scientific method. Peter Apian in 1531 observed that comet tails always appeared to be turned in a direction away from the sun, but the Chinese had recorded this fact about the late 8th century. When Halley's Comet appeared in 837, the Europeans were flocking to church while the more civilized Chinese were observing it with cool scientific detachment. Needless to say, the Chinese were far ahead in the understanding of comets as celestial objects just as are the planets and the rest of the celestial sphere.
The turning point in the history of cometary astronomy occurred in 1577 when Tycho Brahe applied himself to observing the bright comet of that year. His numerous observations proved beyond all reasonable doubt that comets were bodies which moved in the region beyond the moon.
A climax of scientific interest in comets occurred in 1618, when 3 bright ones appeared in rapid succession. The debate concerning their true nature sparked off a great controversy between Horatio Gassi (a Jesuit priest), Galileo, Mano Guiducci (a pupil of Galileo) and later Kepler.
In Keplers work on the paths of the planets, which led to his three laws of planetary motions, he omitted including cometary motion, since a comet could not be continously observed to make a complete orbit around the sun as could the planets in their elliptical motions. With Newton's formalization of his ideas of gravity, the problem of cometary orbits was near to being solved. It was the work of Edmund Halley that finally solved one of the longest-lived mysteries of mankind.
I will stop here with my discussion of comets in history. Next month, I will continue with the story of some remarkable comets in history, including Halley's comet. See you in April.
* * *
OCCULTATION OF SAO 158913 BY SATURN - MARCH 25 Rolf Meier
The most favourable occultation of a star by a planet this year occurs on the evening of March 24/25. The planet is Saturn and the star is of magnitude 8.6. Here is some data on the occultation:
date: March 25, 1984
time of disappearance: 07:41 UT, or 02:41 EST
time of reappearance: 07:54 UT, or 02:54 EST
magnitude of star: 8.6
As can be seen by the time of the event, it is ideally placed for observers in North America. Sky and Telescope (Jan 84 issue) states that it will be difficult to observe because of the faintness of the star relative to Saturn, but this is false. Saturn will be at magnitude +0.7, making for a magnitude difference of 7.9. Compare this to an occultation of the satellites of Jupiter. They range in magnitude from 4.6 to 5.6, whereas Jupiter is at magnitude -2.2 at opposition. The magnitude difference there is 6.8 to 7.8, and occultations of Jupiters satellites are easily observed in even a 2.4-inch refractor. The Saturn event should be easy to see in a 6-inch or larger telescope.
I recommend using high power, because this will dim the image of Saturn, while not dimming the image of the star. (Note that this wont work for Jupiters satellites, because they, too, are extended objects). The star is about as bright as Titan, Saturns largest moon.
Time events as accurately as you can, using a tape recorder and CHU receiver. This is an event which can be readily observed from your back yard.
Thanks go to Malcolm Lambourne for pointing out an error in the answer to question 7) from January. The average number of stars behind the moon is more like 0.03, not 0.1. My error came about as a result of using 0.5° as the radius of the moon, when in fact it is 0.25°, when I calculated the area of the moon in square degrees.
Here are the answers to last month's questions:
1) 96 inches
8) NGC 253
10) Carl Stormer
And 10 more questions:
1) Who invented the Newtonian reflector?
2) What was F.W.A. Argelander's big project?
3) What is the "strangest" nebula in Taurus?
4) How much do the RA of stars typically differ in 1950.0 coordinates vs. 2000.0 coordinates?
5) What is the faintest known star, with an absolute magnitude of +18.6?
6) What is the sun apparently not producing enough of?
7) What is the first white dwarf to be discovered?
8) What planet has periods of continuous lightning and a glow near the surface at night?
9) What type of month is measured from lunar perigee to perigee?
10) What planet was mistaken for a star several times before it was "discovered"?
* * *
Articles for the April issue of Astronotes are due by March 23. No fooling.
* * *
The toilet in the space shuttle failed for the ninth time in nine flights. The General Electric system from Challenger has been shipped to Johnson Space Center for study.