Download PDF version:
The Newsletter of the Ottawa Centre, RASC
|Volume 6 Issue 5 May 1967|
Editor: Dan Brunton
Circulation : Joe Dafoe
2565 Elmhurst Street, Ottawa 14, Ont. 828-14 73
2366 Malone Cresc., Ottawa 5, Ont. 828-7681
The Ottawa Centre is very fortunate in that this year 's General Assembly will be held in Montreal, well with in reach of we Ottawans. There should be a large contingent from our Centre to r e presentus at this Centennial General Assembly. Detailed plans, as they are presently known, are explaine d on page 2 by our president Earl Dudgeon. This General Assembly appears to be a once-in-a-lifetime chance and I hope Ottawa members will take full advantage of it.
Our Centennial observing trip has now been definitely decided upon and we will be travelling to the Picton, Ont. area for what should be a wonderful week of observing and fun. It has been conveniently set in the last week of August to allow those student members,who will be working throughout the summer, a chance to participate. Further details will appear in future Issues, but keep that week open.
A big event for us this past month was Doug O'Brien's wonderful sweep of the awards at the Ottawa Regional S c ien c e F a i r. Not only did Doug win the only first prize awarded at the Fair, $150. in scholarships and two additional citations, but he now
goes on to represent the Ottawa are in the National Science Fair being held at Laval University in Quebec, May 10 to 12, The best wishes of the Centre go with you Doug, and congratulations on a wonderful achievement!
Doug's project and awards will be dealt with in detail in the nex t issue, after the results of the Nationals.
Mr. "Hal" Brock, president of the Astronomy Club of Akron, Ohio and an Ottawa Centre RASC member, has written several very interesting letters to AstroNotes. He included a number of Issues of the Akron G ro u p 's newsletter and several other
enjoyable and informative item s. Mr.Brock has set an excellent example for other distant members (and non-members) by his letters, since any improvement in communications between the numerous groups and in d iv id u a ls that share our interest, is a good thing.
I certainly hope we hear more from the Akron Group.
Have a happy " 'Centennial" May and good seeing.
Grazing Lunar Occultations
Tom Tothill, Co-ordinator; Lunar; Planetary.
The jinx that travels around with one-chance astronomical events was with us on March 16 when the very edge of a weather disturbance fuzzed up the moon for a grazing occultation near Perth.
Six teams were assembled, the site looked good and everyone knew where to go and what to look for. The expedition was cancelled at the las t minute in a close decision, but four good men and true went along anyway.
Basically each team needs a car, a telescope, a radio to play CHU time signals and a tape-recorder to capture both the time signals and the observer's voice saying, "On... Still on...OUT!.. etc., with a prompt estimate of his time lag. The other member of the team keeps track of time, warns the observer when to be ready, makes sure the tape-recorder is running properly, establishes the exact position of site by pacing to mapped points and so forth. Battery-powered equipment is virtually essential, since the site is usually ( and deliberately) a backroad.
We receive comprehensiv e computed data for grazing occultations in our area through the courtesy of David Dunham of Yale University Observatory, with contour drawings by M ille r McLaughlin. Malcolm Thomson kindly passes these along to me and I
acquire the appropriate maps and try to distribute the available teams to best advantage.
Naturally, the more teams the better, and these trips are fun as well being useful.
The graze of April 18th, visible at Panmure near Carp, is even more promising, with a brighter star and a much higher position of the moon. If the jinx permits, we'll give results next month.
Small Dome - May report
Rick Salmon, Co-ordinator, Small Dome.
Lately, work has been done with the new Lunar camera which was constructed by Mr. Tothill. Though unfinished, the camera has already proven a great success and will be left at the Small Dome on a permanent basis by the end of the month.
The camera is a wooden box about a foot long and 6 inches wide; used in conjunction with a one inch eye-piece, it gives a Lunar image of about 3 inches in diameter. At the moment, a 28 mm. eye-piece is on order from Edmund's Scientific.
Photographs already obtained of Jupiter and the Moon are far better than expectations. With a one-and-a-half inch focal length eye-piece, the image of Jupiter is about 1 /8 of an inch in diameter, with the moons extending ½ inch to either side,
while a full Lunar image registers at approximately 2 inches in diameter.
Saturn's New satellite
A new satellite of Saturn ( number 10 ), was reported by Dr. A. Dolfuss of Meudon Observatory. The satellite, which at the time was at it s most eastern elongation, was discovered on December 15 1966. I t is approximately 14t h magnitude and travels in an almost circular orbit of approximately 315,000 km. This new moon was very near the edge of Saturn's ring when it was discovered. Up until F ebruary 1967, 13 photograph s had already been taken by various observatories.
D r. Dolfuss proposes the name "Janus" for the new satellite.
(*** The information for the previous article was found in the January and February 1967 issues of the newsletter for the Astronomical Club of Akron, Ohio)
1967 General Assembly - Montreal - May 19
For this Centennial Year the annual big event of the RASC - the General Assembly - will be held in Montreal. Astronomers, both amateur and professional, will be gathering at the University of Montreal on May 19th to renew acquaintances, discuss some of the activities of 1966, exchange ideas and in the process, to have an enjoyable time.
The General Assembly is the one meeting of the year when members from every centre across Canada get together to share experiences. Displays will show the work of enthusiastic Observers Groups in other centres and papers will be read by both amateur and professional members with new ideas or results to present.
The Assembly will be held at the modernistic University of Montreal on the north side of the mountain. Accommodation arrangements have been made in the University residences so single rooms will be available for only $6.00 a night. This must be almost a record low price at this EXPO time. A package fee of $29.00 covers the Assembly registration fee, three nights at the residence and the annual dinner on Saturday.
A full and interesting programme is being planned starting Friday evening and continuing, until Sunday morning. Details have not all been completed but the following out-lines some of the feature events:
Friday, May 19: Evening - General Assembly meeting, Presentation of awards, Dr. Helen Hogg will give the Petrie Memorial Lecture.
Saturday, May 20: Morning - Papers Session - by members of the Society.
Afternoon - National Council Business Meeting
Evening - 7:00 p.m. - Annual Dinner with guest speaker
10:30 p.m. - Special Showing at the Dow Planetarium - '‘Man and his Star " followed by a reception.
Sunday, May 21: Morning - 9. 30 a.m. - Short bus tour of the city ending at the METRO station leading to EXPO.
Attendance at this year 's General Assembly will provide an unequalled opportunity to combine astronomical interests with a visit to EXPO. Let's see that Ottawa is well represented !
Back Issues of AstroNotes
When I took over the circulation duties of AstroNotes I was given a carton full of back Issues. However, I noticed that for some Issues there were only one or two copies and for several there were none. This, therefore, is a request for the following issues from members who do not wish to save their copies.
Included are also several Issues for which there are sufficient copies and these are available to those members who have only a few issues missing.
July - August 1963
September - October 1963
November 1963 *
July - August 1964
November - December 1964
* No copies at all.
Spectroscopy in Astronomy
A. H. Gillieson
The only information we get from the heavenly bodies, planets, stars, nebulae and galaxies, is obtained through the radiation - lights or radio waves - by which we observe them.
We measure the brightness and distance of these bodies and determine their proper motion without necessarily ap p ly in g spectroscopy, but nearly all other information is obtained by spectroscopic means.
The number of different pieces of information we can discover by attaching a spectroscope to the end of a telescopeand recording and interpreting the resulting spectra is quite astonishing. They include the following :
( I ) Velocity (a) radial i.e. in line-of- sight
(b) rotational - for objects visibly of large size
( I I ) Temperature
( I I I ) Composition - what atoms and molecules are present
(a) by emission and absorption in the case of luminous bodies
e g. the sun, stars, nebulae and galaxies.
(b) by absorption in the case of non-luminous bodies, such
( I V) Size
( V) Mass
(VI) Binary Stars (a ) size of orbit
( VII) Existance and Strength of Magnetic Fields
(V III) Atomic Isotope ratios.
Before the invention of the photographic emulsion, the visual spectroscope was used for the rough classification of the colour of stars and in 1814 Fraunhofer, the inventor of the diffraction grating, recorded the main absorption lines in sun-light. It is worthwhile noting at this point that these early instruments were true " spectroscope s ” - the word is used rather loosely nowadays but strictly refers to an instrument for observing spectra by means of the eye. The spectrograph records the spectra
on a photo g ra p h ic plate or f i lm, and the spectrometer uses a photon detector, e g. photo multiplier, to measure spectral intensities over a very narrow w avelength range.
photographic recording was made use of very early by the Astronomers, and is still the chief tool of the astronomical spectroscopist. Nearly all the vast amount of astronomical spectroscopic information has been obtained by means of the photographic plate. Its introduction permitted accurate determination of wavelength and wavelengthshift of intensities and intensity changes and of distribution of intensity with wavelength.
Essentially only in the last quarter-century has much use been made of photosensitive detectors, chiefly for ultra-violet and visible lights, although work with infrared and x-ray detectors is increasing, particularly for spectroscopy for satellites, which go outside the radiation-absorbing atmosphere of the earth.
The instruments used are many and varied, but fall sharply into two types: ( I ) Prism and ( I I ) G rating instruments.
The prism instrument is the older, and in it, the separation of diffraction of the wavelengths is achieved by a transmission element - the prism.
Prismatic spectra consist of one order only, and are nearly linear with frequency. The grating was discovered a century and a half after the prism and grating instruments were not developed until the turn of this century. Although transmission gratings are made, the reflection type predominates. Grating spectra contain over-lapping spectral orders which can be sorted out by filters or fore-prism s and the spectra are nearly linear with wavelength.
A wide wave-length range is more easily obtained by reflection and the wavelength range of a prism instrument is limited by the transmission of the prism material. For astronomical purposes this limitation has, until recently, been unimportant, since the wavelength range of the visible "’window"' through our atmosphere was adequately covered by glass and quartz prisms.
For both the prism and grating there are a number of arrangements and mountings and the most important and commonly used are the following :
1. Cornu - one o r more 60 degree prism s )
2. Littrow - 30 degree prism with back face silvered) most commonly used
3. Amici )
4. Zenger ) employed in direct-vision and hand spectroscopy
5. Wernicke )
7. Wadsworth ) used in monochromators 7. Wadsworth ) and Spectrometers Grating Mountings
( I ) Concave Grating
1. Rowland - fixed slit )
2. Phasen-Runge - fixed grating and slit ) all astigmatic Rowland
3. Abney - fixed plate and grating ) circle mountings
4. Eagle - fixed slit - most compact ) (concave grating in
5. Radius - fixed plate and slit - used in vacuum ) divergent lights )
6. Wadsworth - fixed slit - stigmatic - (concave grating in parallel lights )
( I I ) P lane Gratings
7. Monk-Gillieson - stigmatic - used in monochromators or Spectrometers (plane grating in divergent lights )
8. Fastie-Erbert - stigmatic - widely used in spectrographs, Spectrometers, monochromators - (plane grating in parallel lights )
9. Czerney-T urner - stigmatic - closely resembles the Fastie-Erbert - much used in the infrared wavelength range.
For small refracting or reflecting telescopes, small direct vision spectroscopes of types (3) - (5) are most practical and replace the eyepiece. With larger telescopes, a fixed, large, high-dispersion instrument may be used at the Coude focus of a reflector or smaller instruments may be attached in place of the eyepiece in the case of a refractor or at the Cassegran focus of a reflector. Large fixed spectrographs are built as an integral part of the spectroheliographs. To obtain simultaneously the spectra of a large number of stars, a thin wedge-shaped glass plate - in fact a prism - is inserted in to a Schmidt or Maksutov telescope, and in place of the usual star images in the wide angle field, small spectra appear for each star.
With a small, direct-vision, low -dispersion spectroscope, the amateur astronomer can make useful observations of the broad differences in the spectra of the various star types. Where the amateur wants to photograph, say the sun, in the lights of the Hydrogen-alpha or Calcium-K lines, the spectrometer mountings are preferable to the spectrographic. Spectrometers are, in general, more compact and can usually be constructed more easily, and more cheaply than spectrographs. They are also preferable when recording is to be made photoelctrically and of those quoted, the Monk-Gillieson (one plane grating and small concave mirror) and the Czorny-Turner (one plane grating and two small concave mirrors ) are the simplest and cheapest mountings to build.
The amateur is of necessity, usually restricted to low-d ispersion instruments, and with these it is not feasible to resolve the spectral lines a d e q u a te ly or to make the measurements of lines h If to r p r of i l e necessary for the determination of velocity, composition, etc., quoted earlier. For such work, high dispersion must be employed, except, curiously enough, for the determination of the red-shift of external galaxies, where the dispersion used is low, although the resolution is high and the spectra are recorded on plates one inch square. The problem here is not spectrographic, but one of light-gathering power.
The methods by which all the eight different kinds of data may be derived from observing spectra must be left as the subject of another article.
* * * * * * * * * * * * * * * * * * * * *
Hillcrest Group Report
On March 3 1967, the Hillcrest Astronomy Club participated in the Hillcrest High School Annual Open house by having a display. The display included the parts in the making of a six-inch reflector; also the parts for the Club 's photo - telescope.
In the meteor section, visitors saw the automatic meteor camera in operation and along with it, the mathematics used in analyzing any good meteor photos. A simulated meteor radar scope was displayed including an oscilloscope and tape recorder. The simulation seemed so realistic that many people believed it to be real radar! Report forms and graphs showed the results of the group 's activities in meteor, a u ro ra and solar observations. The display lasted from 7.00 to 10.00 p.m.
The two inch photo - telescope mentioned above is nearing completion as the optical portion is almost completed. The objective lens is ready to be mounted in the tube and the tube is ready to be mounted on a tripod. All that remains is to assemble the parts for the clock-drive.
In meteor observing, March was the most active month the group has ever experienced for this time of year. During the Easter Holidays, on three nights the group saw 517 meteors. Complete information for F ebruary and March are given in the table below.
(For the group's January observations, see Volume 6, issue 3, March 1967)
Elmvale Meteor Observers Groups
N ig h ts 10 mi n. P e r. Meteors Av.Nos. of Ob s.
February 3 22 28 2
March 5 144 553 5
Total - 1967 12 605 h
presently, the group is p r e p a r in g for the Lyrid and E ta Aquarid showers.
Our o b s e rv e rs are a l s o p re p a rin g to observe the s o la r e c l ip s e on May 9. ( Who knows, it might be c l e a r this tim e ! ) S e v e ra l telescopes, in c lu d in g the s c h o o l 's 2 ½ inch r e f r a c to r and a 4½ inch r e f l e c to r will be used to observe the sun d u rin g the phenomenon. Highspeed Ektachrome and Tri-X f ilm will be used to photograph the e c l i p s e.
Arrangements are being made to to u r EXPO and v is it the Dow planetarium and other attractions in May.
April Observers Group Meeting
The April meeting of the Observers Group was an excellence. Held on the first of April, it saw 34 members in attendance.
Doug O 'Brien and his winning exhibit at the Ottawa Regional Science Fair, was the main to ic of d is c u s s io n. Doug won three different awards and will go on ( to even greater success, we hope) in the national competition this month.
We were also fortunate in having Doug ( with his equipment) at the meeting to show the members basically how it worked. You may remember that in his a r t i c l e announcing the "Observer of the Year for 1966", D r. Fred Lossing suggested the p o s s ib le need for another award, If we had an award "S crounger of the year", Doug O 'Brien would already have won it. It would seem that no two parts of his project came from the same source !
Our Centennial Observing Trip has also been f in a l i z e d, and the results of investigation presented. The trip will be to Picton, Ontario in the las t week of August. More details will appear in next month 's issue.
Two new Co-ordinator s were welcomed at the meeting. Tom Tothillwill tak e on the additional task of planetary Co-ordinator as well as his present job as Lunar Co-ordinator. This arrangement is difficult since he must also run the Observers Group, so if anyone wishes the job of Planetary Co-ordinator, Tom will be very pleased,I'm sure!
The aborted attempt at the March 1 6 th grazing Lunar occultation was mentioned and plansfor the better occultation that occurre d on April 18th were made.
The second Co-ordinator welcomed was Rick Lavery. He will be running the solar group 's activities. With the sunspot cycle becoming very favourab le and the enthusiasm in solar observing rising, this could easily become one of our most active groups.
Some very interesting observational report s were h e a rd from the solar group, the Small Dome and the Elmvale Meteor Observing Group, to round outthe meeting.
Ottawa Centre Library List
Stan Mott, Librarian
(The complete list is too long to include in one issue of AstroNotes without taking up a lot of space. We now have over 100 books in the library, a very good number).
A - General and Introductory
1. The Amateur Astronomer ( 1960) Moore
2. Astronomy ( 1962) Hoyle
3. Astronomy with an Opera Gla s s ( 1888/1961) S e r v is s B rid g e r
4. Astronomy with Binoculars (1963) Muirden
5. Experiments in Sky Watching (1962) Beanly
6. The Fascinating World of Astronomy (1962) Richardson
7. A Guide to the Constellation s (1943) Barton and Barton
8. insight in to Astronomy (1953) Mattersdorf
9. Introductory Astronomy (1958) Sidgewich
10. An introductio n to Astronomy (194 5) Baker
11. Introducing the Constellations (1944) Baker
12. Larousse Encycloped ia of Astronomy (1959)
13. Let 's Look at the Stars (1935) F ro s t
14. Methods of Celestial Mechanics (1961) Brouwer and Clemence
15. Naked-eye Astronomy (1965) Moore
16. New Handbook of t he Heavens (1941) B e rn a rd, B en n e tt and Rice
17. Observational Astronomy for Amateurs (1961) Sidgewich
18. Pictorial Astronomy (1963) A l t e r, Cleminshaw and P h i l l i p s
19. The Sky O b se rv e rs Guide (1959) Mayall, Wyakoff and P o lg re e n
20. The Sky at Nig h t (1964 ) Moore
21. Star c r a f t (1938) Barton and Joseph
22. S ta r Land (1913) Ball
23. The stars in their Courses (1944) Sir J. J e a n s
24. This Universe of Space (1961) Hillman