AstroNotes 1980 September Vol: 19 issue 09

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18

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ISSN 0048-3602
The Newsletter Magazine of the Ottawa Centre of the RASC
Editor.........Rolf Meier .4A Arnold Dr ...........820—5784
Addresses.....Jacqui Tapping...61 Oval Dr., Aylmer...684-1186
The 45th Stellafane convention of amateur telescope
makers was held on August 9 on Breezy Hill, as usual, near
the town of Springfield, Vermont. The 30 or so members
and friends from Ottawa were among the reported 1500
registrants who attended this year. A large (record?)
number of 58 displays were entered this year. Competition was quite good, especially among the conventional
Newtonian class. Unfortunately, no Ottawa entry won any
awards this year. Weather was hot and humid, but it was
clear enough on Saturday evening to perform the optical
judging.
In past years, sophisticated electronics began
appearing on many entries. This was lacking this year.
Has the novelty worn off, or have telescope builders
decided that the great effort involved is not worth the
re suits?
I believe that properly-designed electronics can
make for an excellent telescope. The basis of such a
system would be a microprocessor-controlled drive. To
be even more impressive, such a system could be installed
on an altazimuth mounting. Such a mount would require
little mechanical complexity, and yet would benefit from
great stability. The greatest tasks would be to figure
out the proper tracking algorithm, and the driving method.
With a little extra effort, a method of position readout
and automatic slewing to a predetermined position could
be added.
With inexpensive and complex components that are
available today, all that would be required is a great
deal of thought. The result would be a unique amateur
instrument worthy of respect, and a sure winner at
Stellafane.
Vol. 19, No. 9 $2.00 a year September, 1980
Circulation...Barry Matthews...2237 Iris St • • • 225-6500
EDITORIALThe August meeting, held in room 3001 at the Sussex Dr.
NRC, was attended by only 35 people. Rob Dick called the
meeting to order at 8:15 pm, and opened the meeting with
the announcement that active member Mike Roney will be
leaving the group for a 2-year work stint in Africa. Mike
will be employed by a CUSO teaching team in Sierra Leone.
A round of applause was given to Mike, and chairman Rob
Dick thanked him for his contributions to the group.
Other announcements included: Robin Molson has
fixed the door frame at IRO; Bill Donaldson and Jim Zilinsky are looking for visual correlation on their solar
radio noise observations - sunspot counts, flares, and
aurora sightings can be used to help them in this project.
A report by variable star/meteor coordinator Rob
McCallum began the meeting's observations session. Rob
announced that observations of CY Aquarii have already
started at the IRO. It is a good star for practising
estimates by the rookie observer. It is easily-observed
in a 6-inch telescope. (See the July, 1930 issue of
Astronotes.)
The Perseid meteor shower will definitely be observed
from the IRO on August 11. To quote Rob, "Anyone in their
right mind will go."
The Gatineau hills will never be the same again.
Planned for Saturday, September 6, is the first (annual?)
Observer's Group picnic. Masterminded by Rob McCallum, it
will take place near Kingsmere, P.Q, at the Booth Picnic
Grounds. Scheduled to start at 4 pm, the festivities will
include an informal softball game, the barbecue, and then
an observing session. There is no "rain date" for this
picnic, according to Rob, "because it’s not going to rain."
Brian Burke informed all present where they could
find the planets during August. Other interesting events
included the dichotomy of Venus, the penumbral eclipse of
the moon, and planned observations with photometers of an
occultation of a 5th-magnitude double star.
Brian then described a new astronomical organization,
International Amateur and Professional Photoelectric
Photometry. Observational programs and techniques, as
well as amateur and professional equipment, will be reviewed in the IAPPP newsletter, Communications of the
IAPPP. The primary objective of this newsletter is to make
amateur observations available to the professional
scientific community. For more details on membership,please see Brian.
Brian ended h is stay at the podium by informing
members of 2 upcoming grazing occultations, on
September 17 and November 1. Brian will give a talk
on preparing for grazes at the September meeting.
Rob McCallum returned to the front for a slide presentation on the RASC General Assembly, which was held in
Halifax, Nova Scotia. Highlights of his talk included
quotations from a speech by Dr. Percy, the relative calm
of the annual business meeting, slides of displays, and
slides of some Ottawa members receiving various awards.
Two other slide talks closed the observational
session. Frank Roy showed us what the IRO and Fred’s
shed looked like from 800 feet up. Brian Stokoe briefly
displayed "candids" of Venus, Mars, Jupiter, Mercury,
Saturn, and the Trifid Nebula.
Before the meeting adjourned, Ted Bean, our
Mr. Hospitality, announced that the "happy hour” following
the meeting will now be hosted by Ann (Mrs. Art) Fraser.
On behalf of all members, Fred Lossing extended warm
praise and a gracious vote of thanks for Ted's dedicated
service (which has amounted to more than five years in
this role). It can easily be said that Fred’s motion of
thanks was more than seconded. Thanks again, Ted Bean!
The meeting was then adjourned by the chairman
at 9:51 pm.
#########
TED BEAN RETIRES Frank Roy
If anyone has ever attended an Observer* Group
meeting they have had coffee, coke, or cookies, known as
the three C's, after the meeting. The task of providing
them has been carried out by Ted Bean for many years.
(Before Ted, Ken Perrins did it) Everyone who has used
Ted's service thanks him very much. It requires some
dedication to be present at every meeting and serve the
group. Ted also served refreshments at Centre meetings
and council meetings. Ann Fraser will be taking over the
service as of the September Observer's Group meeting. We
all thank Ann for donating her time.
Ted has missed the end of the meetings since he has
been doing the "hospitality" chores, but now he will be
enjoying a whole meeting.
#########The first annual Symposium of International Amateur
and Professional Photoelectric Photometry (IAPPP) was held
in Dayton and Fairborn, Ohio on June 12-14, 1930. The
Symposium was attended by both amateur and professional
astronomers and was chaired by Dr. Douglas S. Hall,
Professor of Astronomy at Vanderbilt University. The
meeting was hosted by the Fairborn Observatory and the
Miami Valley Astronomical Society. The IAPPP was formed to
provide a means of communication between amateur and professional astronomers involved in astronomical photoelectric
photometry.
Anyone interested in photometry is invited to join
IAPPP. Annual dues are $10 and members will receive and
can submit contributions for publication in the IAPPP
Communications.
There will be four regular, full-size Communications
each year and short, extra issues will be published when
required. Contributions for publication are solicited in
the following areas: 1) Suggested observing programs of
current scientific interest to professional astronomers
and suitable for amateur photoelectric photometry,
2) Equipment design and construction, 3) Observational
and data reduction techniques, 4) Questions from and
answers to questions from new amateurs, 5) Descriptions
of small observatories equipped for photometry, 6) Reviews
of recent articles, meetings, and equipment relevant to
photometry.
If you are interested in joining the IAPPP, send your
dues and any questions you may have to:
Mr. Russell M. Genet
Fairborn Observatory
Fairborn, Ohio 45324
The membership fee should be in U.S. currency.
#########
Articles for the October issue of Astronotes
are due by September 19.On Tuesday, September 16, there will be a favourable
grazing occultation of a 6.9-magnitude star known as
132 B. Ophiuchi. The time of the graze will be at 21:30
EST. Although the nearest point is about 30 km north of
Ottawa, the best location appears to be just west of
Arnprior, approximately 70 km from Ottawa. The Arnprior
location is the better of the two sites because there will
be fewer trees to contend with since the elevation of the
moon for this graze is only 13 degrees. The graze will be
on the dark southern limb and the moon will be 45% sunlit.
The equipment required for the graze are telescope,
tape recorder, and most important, a dependable radio
that receives the CHU time signal. Anyone interested in
participating in this graze expedition, please give me a
call at 521-8856.
#########
MID-JULY PUBLIC STAR STAR NIGHT Brian Burke
On the evening of Friday, July 18, a public star
night was held in a park at the corner of Lynda Lane and
Billings Avenue. Although there were some clouds at the
start of the evening, they cleared off enough to allow
views of the moon, planets, and some deep sky objects.
About 50 people came out to look through the telescopes
that had been set up. The telescopes ranged in size
from 7.5 to 30 com. The majority were built by members
and this certainly intrigued many of the people there.
Overall, the night was quite successful and we inted to
have more public star nights in the city in the future.
#########
Do you want to build a telescope but don't know
where to get the parts? Send for the free catalog
from Edmund Scientific Company. They sell all the parts
you require, as well as books on telescope making.
Write to:
Edmund Scientific Co.
7082 Edscorp 3uilding
Barrington, N.J. 08007
United StatesRADIO ASTRONOMY - BASELINE FORESHORTENING Frank Roy
During normal operation the IRORI resolves the sun.
Usid in the phase-switched interferometer mode our radio
telescope does not "see" sources larger than one lobe
width. The sun at our frequency of 238.5 MHz has a diameter of about 0.6°.
One lobe width in degrees = 57 x lambda
D
where lambda is the wavelength in metres
D is the baseline in metres
57 x (1.26) = 0.4°
180
We can see that the sun is resolved, since 0.4° is
smaller than 0.6°.
The antennas are more sensitve in some directions.
The sensitivty pattern is called the polar diagram.
There is one main lobe at the meridian and two
smaller ones 4h (60°) in RA on either side.
What happens if a source is picked up in a side
lobe? A radio source overhead is seen by the full baseline
of 180 metres but 4h in RA away in a side-lobe is seen
only a fraction of this, because the source is seen at
an angle of 60° to the real baseline.
The incoming wavefront B':
B' = cos(60°) x B
= 90m
Our lobe width will now be:
57 x (1.26) = 0.8°
90
The interferometer no longer resolves the sun since
0.8° is larger than 0.6°.
#########COMPUTING THE HELIOCENTRIC CORRECTION Doug Welch
When dealing with observations of astronomical
phenomena which have characteristic time scales of less
than a day, it is often necessary to take into account the
effects of the earth’s position around the sun and the
finite velocity of light. Specifically, a signal from a
distant object, travelling at the speed of light, will
arrive at different times at different portions of the
earth’s orbit. Light takes about 1000 seconds to cross
the diameter of the earth’s orbit and hence this is the
maximum effect possible. The usual solution to the
problem of obtaining a consistent time reference is to
list the time of observation as the time at which the
signal would arrive at the sun. I will develop here the
simple relation needed to produce this correction.
Consider the situation in a geocentric rectangular
reference frame. In the usual sense,
the x-axis points toward RA 0h, Dec 0°
y-axis points toward 6h 0°
z-axis points toward 90°
If RAstar and Decstar are the objects’s right
ascension and declination respectively, then a unit
vector in the direction of the star will have the
following components:
x * = cos(RAstar)cos(DECstar)
y* = sin(RAstar)cos(DECstar)
z * = sin(DECstar)
Now if we go to the American Ephemeris and Nautical
Almanac for the year and date in question, we c m find
the conponents Xsun, Ysun, and Zsun of the position
vector of the sun. The situation is illustrated in the
accompanying diagram.
A little knowledge of vectors tells us the
following:Light travels 1 AU in 499 seconds and there are
86400 seconds in a Julian day, so the correction has the
value following:
Let’s do a real example. CY Aquarii is located
at RAstar 22h 35.2m, Decstar 1° 17'.
Several maxima of CY Aquarii were observed during
the night of July 24, 1980, in the hours around 6h UT.
From the AENA for 0h July 24 we have the following:
This is reasonable because CY is about a month from
opposition, and hence a signal from CY would reach the
earth before the sun.
If you require the solar rectangular coordinates in
the 1950 system, I can supply them for copying costs.
#########10 YEARS AGO IN ASTRONOTFS
From the September, 1970 issue: "Owing to a 'fortunate
conjunction of the planets', our dreams for the 16-inch
telescope are coming to an unexpectedly rapid and
satisfactory fruition. We are going to get not just
one mount, but two. The first will be a fork mount
of light but satisfyingly rigid design, employing
aluminum tubing and weldments of steel shafts. Its
cost will be such as to leave the telescope fund substantially intact, and there is no doubt that a good,
usable mount with drive will be available to us in a
few months. The bulk of the fund will be used to build
a second mount - a ball-mount design which involves
a certain amount of pioneering but which the Telescope
Committee feels has some real potential if done right and
in not too much of a hurry."
#########President
R. Wlochowicz o f C a n a d a J . Tapping
996 - 9345 684 - 1186
822 - 1799
100 Sussex Drive, N.R.C., xxxxxxxxxxxxxx Ottawa K1A 0R6, Ontario.
xxxxxx
LECTURE MEETING
DATE: Tuesday, September 23, 1980 TIME: 8:00 p.m.
A FILM SHOW
(1) Powers of Ten (10 minutes)
A very interesting illustration of the vast range of scales of
the universe, from the sub-atomic to clusters of galaxies - and beyond....
(2) Relativistic Time Dilation (10 Minutes)
A good description of some of the aspects of special relativity
(3) Changing Perceptions of the Universe (30 minutes)
Our picture of the Universe is always changing. New observations are constantly revealing things that were previously unexpected. By
the time a film is prepared, it is inevitably out of date, but this one is a
very interesting survey of recent concepts.
(4) Spaceborne (15 minutes)
Since the movie camera was first taken into space, some
fascinating and beautiful things have been filmed. This film shows some
material which is not available elsewhere and should not be missed.
The above film show will be held in the Main Auditorium, N.R.C., 100 Sussex Drive
Ottawa.
COFFEE WILL BE AVAILABLE. VISITORS ARE WELCOME.
Please note that whenever possible, meeting notices and other information sheets
will be distributed inside "Astronotes".
ROYAL ASTRONOMICAL
SOCIETY
OF CANADA
SecretaryASTRO NOTES
TO MS. ROSEMARY FREEMAN CAST
NATIONAL SECRETARY
THE ROYAL ASTRON. SOC. OF CAN.
124 MERTON STREET
TORONTO, ONTARIO M4S 2Z