AstroNotes 1973 February Vol: 12 issue 02

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A S T R O N O T E S
Vol. 12 , No. 2
$ 2 . 00 a year
February, 1973
Editor: Tom Tothill    22 Delong Drive, K 1 J 7E 6
Addresses: Mary Grey    Dom. Observatory, 994-5474
Circulation: Ted Bean    399 McLeod Street, K2P 1A5

 

SATURN AT ITS BEST
 Tom Tothill
If Taurus looks a little odd to you these nights, blame Saturn, high up there in the superb winter sky. It is unusually bright for three reasons: it is near perihelion; it is near the maximum opening of the rings; and it is on a high part of the ecliptic. In the 16-inch it is uncomfortably bright and you may see it better in your 4 to 6-inch, or in the 3-inch guide scope on the 16-inch, unless you want to identify the moons, for which the Sixteen and a good patch of seeing are invaluable.

Sooner or later someone is going to come up with an explanation for the extraordinary features of Saturn. Not only are its rings unique, extraordinarily thin, and divided into several bands, but Saturn is calculated to be incredibly light for its size - lighter than water. If it is a ball of gas, without a solid core, then where did the material of the rings come from? They consist of solid particles in orbit around the planet, the outer ones moving more slowly, as may be expected, than the inner ones. They are exactly in the plane of Saturn's equator, whereas most of the moons are in slightly inclined orbits. Are the rings an indication to us of how moons form in the solar system? In other words, will the rings eventually ball up into one or several more moons of Saturn, or do they represent a former moon of Saturn that broke up, splaying its contents into the rings?

Saturn's position next to Jupiter in the solar system, even though they are currently never closer than about 3.8 a.u., leads to a phenomenon called "The Great Inequality" in celestial mechanics. They perturb one another in a period of (if memory serves?) - about 900 years, during which the eccentricities of their orbits change significantly, so that at tines they are closer together.

Go take a look - and then, by all means, think.

OBSERVERS GROUP MEETING - JAN 5 Cathy Hall

In the absence of our new chairman, Tom Tothill opened the first meeting of 1973.
 Announcements were made concerning the Dinner meeting, nominations for the 1973
Ottawa Centre Council, and the  coming Centre meetings,Dr. Iwanowska on Jan 8 and Dr.
 Sidney van den Bergh on Feb 22.

Ted Bean started the observing session off by calling upon Barry Matthews, who suggested various solar activities that could be carried out with and without the use of a balsa-wood projection box. Try them! Also, as New Member Coordinator, he asked all observers (not just solar) to please fill out one of the activity check-lists at each meeting. These are to give the coordinators some idea of the observations made in their field. Do the coordinators know what you are doing?

Progress on the quasar (OJ 287) program was given by Rob Dick, with a little help from his friends (!). Slides courtesy of Rolf Meier,

Our new Graze coordinator, Karl Poirier, explained what exactly grazes are and what can be done in the way of observations. None for the present time, but don't put your scopes away.

Allen Miller and his Star Truk Co. showed their colour film of the Apollo 17 launching ... complete with shock waves! It was positively excellent. Slides of the trip followed, taken by Rolf Meier.

In closing, Ted Bean announced the awards for 1972 - Observer of the Year Award: Ken Hewitt-White, Merit Awards: Stan Mott and Ken Perrins, and Variable Star Award: yours
truly.

* * * * * * * * * * * * *

MR. ROMEO WLOCHOWICZ ON MICROMETEOROID RESEARCH

By an oversight, we managed to make no mention last month of Mr. Wlochowicz' discourse on micrometeoroid research on Nov 29. It was well illustrated with both slides and hardware developed to collect these elusive particles from the upper atmosphere with rockets and balloons. A lively question period followed the talk.

FINDING THE HORSEHEAD NEBULA     Rolf Meier

The Horsehead Nebula is a famous object but few amateurs even know where to look for it. It is familiar to all, for a photograph of it appears in almost any astronomy book, labeled "The Horsehead Nebula in Orion". A common mistake is to confuse the dark portion of M 42 with the Horsehead, There is a name for this also, "The Fish's Mouth", but it is not such a gift to look into as the real Horsehead's mouth. The error is not without reason for there is a similarity, and the position is rarely described more accurately than "in Orion". While M 42 is the brightest galactic nebula we can see, the Horsehead is a dark nebula, visible because it is projected upon a brighter portion of the nebulosity.

The Horsehead is near to M 42, only a few degrees north of it. See the finder chart opposite to see exactly where it is. Faint stars are included in the region near the
Horsehead so as not to confuse and confound. The three bright stars will be immediately recognizable as the belt of Orion. Note the nebulosity surrounding some of the stars.

The greatest difficulty in finding the bright streamer that the Horsehead is projected against is caused by the glare from the star Zeta Orionis which is 2nd magnitude and only half a degree away. It is best to put the star just outside the field of view to minimize this effect. Clean optics are a must. Since the Horsehead is there in winter, the eyepiece is very susceptible to fogging up, so watch this. You should use the power with your best relative light efficiency, i.e. a power low enough to provide a bright image, and high enough to have an exit pupil less than 7 mm in diameter.

There is almost no hope of seeing the Horsehead in the city. I stress that skies must be absolutely dark. It will not be seen in small scopes and I would say that a 6-in is the very smallest that may show it under the best conditions. In fact, it has only occasionally been glimpsed in the 16-inch.

The first thing to look for once Zeta Orionis is identified is NGC 2024, just to the east. This is a fairly bright object, but for some reason somewhat neglected.

FINDING THE HORSE HEAD NEBULA

Then, using the map, identify some of the bright stars to the south. Some of them are surrounded by faint nebulosity which is hard to discern from scattered light, but in some cases it is real. Again using the map, find some of the fainter stars that outline the Horsehead and brighter background nebula. You may not see either, but that is not unusual.

The Horsehead is easier to photograph than to see. The background nebulosity of IC 434 is bright red in colour (from ionized hydrogengas) on High Speed Ektachrome, making for easy visibility. In fact, it is better to photograph in colour than black and white because films such as Tri-X are more sensitive to blue than to red. As a guideline, the following exposures are good:

Tri-X                f/2.5        15-20 min.
High Speed Ektachrome        f/2.5        10-20min.

The Horsehead shows up well with an ordinary 50 mm lens. It will show up as long as the sky-fogging limit is not exceeded.
* * * * * * * * * * * * *
VARIABLE STAR AWARD - 1972 Jon Buchanan

Miss Cathy Hall is this year's winner of the variable star plaque, presented for the most observations of the nine stars: G Her, X Her, RR CrB, W Ori, CK Ori, TX Psc, R Scuti, RX Leporis, and U Mon. As a new variable-observer this is quite an accomplishment.

The top three observers and their totals follow:
        C. Hall     346
        K. Hewitt-White 294
        R. McCallum     198

The variables to be observed towards the 1973 award will be discussed at the February meeting.

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CHU COMES TO NORTH MOUNTAIN
Through the kind donation of one of our new members, Rene Beaudry, a CHU receiver has been installed at N.M.O.

GO WEST YOUNG MAN, GO WEST Ken Hewitt-White

In the spring I went west to Vancouver for the General Assembly and fell so much in love with the city that I vowed to return. I have so many astronomer friends out there (in fact, my girl-friend is one of them) and they wondered when I was going to come and give a talk some time. Thus armed with the excuses to go, I hopped aboard the ol' 747 after Christmas and went out to pay my respects.

Vancouver itself is a well-contained city with a gorgeous setting but unfortunately its municipalities stretch for ever to the east. Getting good dark skies in less than an hour's drive is therefore very difficult. The Vancouver Centre does not have an observer's group due to problems like these but with the kind of enthusiastic types that I have met out there, they nay very well soon have. One way to do this is through the local newsletter, Nova News. Dave Dodge is the new editor and he remarks that the new expanded version will be accepting articles from all over. So if you have a tidbit, send it along.#

I gave a talk on our Observers Group at their Jan 9 meeting. At that meeting, plans for an astrophotography group were begun. With picture-taking such an oft-practiced art in Ottawa, perhaps we should look into such a group, too? Before I left Vancouver, I was treated to a planetarium show, sitting with the operator. I was allowed to twist a few dials myself; that's a mighty powerful feeling there, knowing you can get rid of Murphy with the twist of a dial!

On January 8, I was in Edmonton to visit with Franklin Loehde and the Edmonton Centre. Here was the official excuse for my trip west: delivering my Gen. Assy. paper again. But the greater portion of time seemed to be spent on talking about astronomy in the Centres and how each group might improve its lot. One thing certainly does no harm; actually visiting another Centre. If you are in some other city this year, why not drop in to see the local RASC? I had a great time; thanks to all those who extended their hospitality.
* * * * * * * * * * * * *
# Retaining your best stuff, however, for this rag.-Ed.

VARIABLES (5) Jon Buchanan

Given the following information, what could you determine about a variable? A period of 15 days, a maximum magnitude of 11.3, a minimum magnitude of 13 . 5 , and the
star is a Cepheid.

If you don't know what can be determined, I'll tell you: the absolute magnitude and the distance of this star. How? you might ask. Read on.

Cepheids, like other types of variables, can be divided up into different classes dependent on several characteristics. Population I Cepheids (those in the galactic arms) are very luminous super-giants, spectrally class F to G, with absolute magnitudes around -2.5 to -5, as are other Cepheids, These stars generally occur once per two million stars, giving them a statistical distribution of one every 100 parsecs. Generally the greater the luminosity, the greater the colour index and the later the spectral type.

Periods range from slightly more than one day to 50 days, with the periods being constant. Thirty percent of this time is spent in brightening.

Type II Cepheids are another group, similar in every respect to the other Cepheids except that they are generally 1.2 magnitudes fainter for the same period. These are Population II stars, being found in clusters or alone in the galactic halo. These can be further sub-classed into W Virginia and RV Tauri types.

W Virginia stars have periods from 10 to 30 days. Their light curves are shaped differently and they have double absorption lines for part of each period.

RV Tauri stars have periods of 30 to 150 days. Their pulsation is less regular than those of shorter periods and some show occasional doubling of spectral lines.

Another type of Cepheid is the RR Lyrae type mentioned in last month's article.

That is some of the information on Cepheids, but one important part has been left out - namely, the fact that the brightness and the period of Cepheid stars are related. This fact was discovered by Miss Henrietta Leavitt at the start of this century while studying numerous photographs of the Small Magellanic Cloud, A luminosity/period relationship was found for numerous Cepheids in this cloud, and given the fact that all of them are at the same distance from Earth, to within a small error, then this relationship falls automatically into place. Since a Cepheid is a Cepheid whether it is in the Small Magellanic Cloud, in our galaxy, or in another galaxy, they must all obey this rule. What remains to be done is to find the absolute magnitude of a Cepheid of known period, or its
distance, so that the relationship of luminosity to dis­
tance can be applied.

M = m - 5 log(r/ro )

where M is absolute magnitude, m is the visual magnitude, r is the distance of the star and ro is 10 parsecs, or the distance at which the absolute magnitude and the visual magnitude are equal (i.e., the distance to which absolute magnitudes are referred).

Since the distance of the Small Magellanic Cloud was unknown, and since the distance of any Cepheid can't be measured directly (as with parallax) only indirect methods can be used, and thus the absolute magnitude may be out, as was discovered in 1950.

A graph of the various Cepheid types is given below where the average absolute visual magnitude is plotted against the log of the period (log to base 10).

Given the period of a Cepheid you can interpolate its absolute magnitude. With this and the average visual magnitude and the equation for determining its absolute magnitude (given above) you can work out the distance of the star in parsecs.

The formula may be rewritten as: log(r/ro = (m - M)/5
which reduces to: r = ro x 10(m - M)/5
where ro = 10 pc

Let's return to the original question asked at the start of this article. A Cepheid, assuming it to be of Population I, with a magnitude range of 11.3 to 13.5, or 12.4 average magnitude. Therefore m = 12.4

It has a period of 15 days,  Log(15) = 1.1761 or about 1.2

Looking at the graph for Pop. I Cepheids we find an absolute magnitude range of about -4.0 to -4.4, so we'll let M - -4.2

    Then m - M = 12.4 + 4.2 = 16.6
    16.6/5 = 3.3 approximately.
    So  r = 10 x 10^(3.3) = 1.995 x 10^4 = 19,950 parsecs

Therefore this star is roughly twenty thousand parsecs away!

If you wish to practice this some more, here are several other Cepheids to try. XZ Cygni, an RR Lyrae type star, was written up by Ken Hewitt-White in the October'72 issue of Astronotes. It has an average magnitude of about 9.5, and a period of 11.5 hours. (Since it's an RR Lyrae type, absolute magnitude is +0.5).

Another Cepheid, this time a Type II Cepheid, was "found" by Allen Hiller on the night of May 25, 1970 (Sept '70 issue of Astronotes). It is one of the Cepheids of M 5 , a globular cluster, with a period of 28 days and a peak magnitude of 10.6 . Assume an average magnitude of 11.0 or anything down to 11. 5 . With this you can determine the distance of the cluster M 5. (Don't forget, 1 parsec = 3.26 light years!)

Another Cepheid, this time a Population I star, is Polaris. It has a period of 4 days and an average magnitude of about 2 . 1 . Unfortunately this value does not compare exactly with that listed in the Handbook. Using the Handbook values for M and m you get a more exact value.

DR. IWANOWSKA ON NICHOLAS COPERNICUS - JAN 8

We were fortunate to have a visit by Dr. W . Iwanowska who is the Director of the Institute of Astrophysics in Torun, Poland, the birthplace of Copernicus. Her address to the Centre in celebration of the 500th anniversary of the birth of Copernicus was attended by a large audience drawn from the Royal Society of Canada and the Polish community as well as ourselves, at the NRC Auditorium, Sussex Drive. A second reason for her tour of Canada is to obtain a high-dispersion spectrograph for Torun from the optical workshops of the Dominion Astrophysical Observatory, Victoria B.C., and we understand that donations towards this worthy cause would be welcome.
* * * * * * * * * * * * *

ANNUAL MEETING AND DINNER - JAN 16
Ninety four members and guests attended a pleasant dinner at the Sampan Restaurant, followed by reports from the Officers, presentation of Awards, and elections of
the new Council. The new slate is:

Honorary President:    Dr. C.S. Beals
President:        Mrs. Mary Henderson
1st Vice President:    Mr. R.W. Tanner
2 nd Vice President:    Mr. K. Perrins
Secretary:        Mrs, M.W. Grey
Treasurer:        Mr. R. Wlochowicz
Librarian:        Mr. S.A. Mott
Recorder:        Miss C. Hall

Councillors:        Mr. T.E.D. Bean
            Mr. J.M. Grant
            Mr. J.L. Horwood
            Mr. E. ter Heijden
            Dr. D.W. Sida

Membership Certificates were awarded to Mrs. A.F. Cook (the former Joan Stewart, Recorder of the Centre), Jack M. Grant, Mrs. Mary W. Grey, A.A. Griffin, Dr. D.A. MacLulich, W.J. Medd, F.R. Park, and R.W. Tanner.

The Observer of the Year was Ken Hewitt-White (again), and the Observers Group's Merit Awards went to Mr. Stan Mott and Mr. Ken Perrins. Variable star Plaque: Cathy Hall.

DR. LOCKE ON "EXPLOSIONS IN ASTRONOMY" - JAN 16

The title of Dr. Jack L . Locke's address to the Dinner meeting had both figurative and literal connotations, since he reviewed the recent explosion in knowledge associated with the modern discoveries in pulsars, quasars, neutron stars, radio sources, and black holes the existence of which has not only been postulated but also (perhaps) proved by the existence of double stars only one component of which can be detected. The possibilities of a joint French and Canadian telescope on Mauna Kea, Hawaii, at almost 14000 ft are being explored.
* * * * * * * * * * * * *

A NON-FOGGING EYEPIECE Rolf Meier

After many frustrating attempts at clearing a fogged-up eyepiece on cold, damp nights (or a frosted-up eyepiece on even colder nights), it became evident that some automatic process was necessary. Usually one would wonder why everything was becoming very faint, or why every star would look nebulous. Wiping the eyepiece is unthought of and, resisting such temptation, one warms up the eyepiece to evaporate the moisture either by bringing it inside (which fogs it up even more at first), or with an electric hair drier (very efficient but quite clumsy).

Then, on a cold, frosty night, while beautiful ice crystals were forming on the eyepiece obscuring certain areas of the field of view, the obvious solution came to me. The next day I built a prototype for a heating element to fit in a certain eyepiece I had in mind.

The heating element consists of a 2" (approx) length of high-resistance nichrome wire. It is wound into a single coil, and fits inside the eyepiece. The particular one that I built works best for the eyepiece it was designed for, a 20 mm Kellner shown in the diagram. It is important that the coil does not touch any part of the eyepiece. It is just suspended in air by the insulated wire leads. It works best for this eyepiece because of the almost enclosed pocket of air which surrounds the heating element.

The power supply must be very small, not quite enough to let the wire glow, about one volt. To check on how much heat the unit is giving off while in operation, it may be a good idea to put an identical coil in series with the circuit externally, and observe how it behaves.

Will the heat produced affect the image quality? As far as convection currents ar e concerned, the effect is indeed small. Power consumption is only one or two watts, while the observer himself emits up to 40 watts, largely in expelled air. However it is quite likely that the lens elements are distorted if the eyepiece is very hot. Then the voltage should be at a minimum, just enough to keep the eye lens warm enough to prevent condensation of water vapour.

I have considered the application of internal heating elements - for instance, some very thin nichrome wire can be used to make self-illuminating crosshair eyepieces, while warming the eyepiece at the same time. Perhaps someone can develop this idea better than I can, because I can foresee some technical problems.
* * * * * * * * * * * * *

Apollo Pictures Available
Due to popular demand I am making ray slides of Apollo 17 and Kennedy Space Center available for copying. To avoid financial loss, I would like some firm committments before all kinds of copies are made. I have more views than were shown at the January meeting. Call anytime and leave a message if I am not home.
-Rolf Meier
224-1200
* * * * * * * * * * * * *
BEGINNERS CLASS AGAIN IN FEB
Friday, Feb 16, at 8:00 pm. Topics "Finding objects".

CLOUDED OUT
 Barry Matthews
"Clouded Out" is a review of books and periodicals available from the Centre's library for nights that are no good for observing. I feel that I really missed the boat for the Dec Astronotes as we spent the greater part of the month under 10/10ths cloud. The point is that all volumes reviewed in this article are available (to paid up members) for the asking from our "Meritted" librarian Stan Mott. It really pleases me to hear some observer say: "Oh yes, I read your article in Astronotes, got the book from Stan and really enjoyed it." Keep it up. Even negative comments are better than no comments.

This month I would like to go back to one of my favourite authors, Patrick Moore. "The Amateur Astronomer", #209, has rejoined the not-too-dusty shelves of our Library as a 7th edition. This newly revised book follows the Moore tradition of presenting the facts in an easy-to-follow fashion and not tiring out the reader.

Patrick Moore has related his many years of amateur astronomy to those who would like to join the ranks of amateur astronomy and would like to know how to go about it. Not only does Mr. Moore write with an ease of style but presents the reader with a quick and thorough reference volume, "The Amateur Astronomer" contains maps, charts, and tables required by the observer to make himself useful to others. To quote Mr, Moores "In fact, it is the complete and indispensable guide for the amateur astronomer - both the beginner and the experienced observer - who will find a mass of invaluable advice."

The next time you are clouded out, "The Amateur Astronomer" by P. Moore will help to pass the time until you can get some scope time.
* * * * * * * * * * * * *

In place of the promised article on entrance slits for spectroscopes I would like to recommend a booklet "The Sun in H-Alpha Light with a Spectrohelioscope" by Fredrick N. Veio. Mr. Veio has carried on a one-man campaign to design spectroscopes and make them available to amateurs. This booklet costs $1.50 U.S. from: Fredrick N. Veio, P.O. Box 338, Clear Lake Park, California 95424, U.S.A.

THE SCHLOSSING SAGA (19) Tom Tothill
"Stein Ein. How about a beer?"

Schlossing was taken completely aback by the totally unexpected message from the coffee machine, and it must be admitted that to sit with one's mouth agape when one has been munching one's fluffed peat for breakfast is a tricky operation. He looked at the clocks, noting that the Talk-Home one had switched off its light. That meant, he supposed, that the bulb was dud, but a check soon showed that it was good and had been switched off by the System, Maybe it meant that there was no use trying to talk home any more. He looked behind, and sure enough the sun and planets had disappeared into an expanding black hole, blacker than the ace of spades.

What about the Hear-Home clock? It was still lit, but had stopped. Staring at it for a while, Schlossing was astonished to see that it was going ever so slowly backwards. At least, the third clock was functioning all right, still keeping good time with his watch. Perhaps he could use that when everything else seemed to be failing.

The view ahead was quite extraordinary. Planet X, now big and bright enough for a good view, was rotating at a fantastic rate and had gone blue all over. The constellations were almost unrecognizable with so many stars dimmer or brighter by several magnitudes, and off to the side they were all squashed out of shape.

The next shock was even worse. Here he was, nearly half way to Planet X, or nearly a quarter of the round trip, and the fuel gauge was reading 1⁄2 full!

"Redfern," he said severely to himself, "We've got a problem!" and had his beer.

Back at the ranch, meanwhile, Floyd Biggs had for several days been studying his plots with increasing consternation. Schlossing's velocity was failing to follow the asymptote, but instead headed straight for the speed of light. Finally he called Hotpill in a state of great excitement: "Schlossing just violated relativity" , he said.

"Relativity Who?" said Hotpill, but Biggs was speechless and he never did find out.

ASTRO NOTES
TO: Ms. Rosemary Freeman
National Secretary
The Royal Astronomical
Society of Canada
252 College St.,
Toronto 130, Ontario.