AstroNotes 1982 May Vol: 21 issue 05

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ASTRONOTES ISSN 0048-8682
The Newsletter Magazine of the Ottawa Centre of the RASC
V ol. 21, No. 5 $5.00 a year May, 1982
Editor....... Rolf Meier.......4-A Arnold Dr......820-5784
Addresses.... Art Fraser...... 11-860 Cahill Dr...737-4110
Circulation...Barry Matthews...2237 Iris St....... 225-6600
OBSERVER'S GROUP MEETING - MARCH 5 Dave Fedosiewich
Chairman Rolf Meier opened the meeting at 8:18 pm with
46 people in attendance, 36 of whom were members. Rolf
invited members and their friends to attend the March star
night, to be held on March 20 or 21. He also reminded the
group that there were still some Observer's Manuals for
sale at their regular low price.
Vice-Chairman Rob McCallum took over the observational
section of the meeting with a reminder that the General
Assembly is not far off. The Ottawa Centre has the habit
of walking off with most of the prizes every second year,
and it's our turn again.
Our Solar Coordinator Rob Dick has much aurora
activity to report. Dave Lauzon alerted Rob about a nice
display around the 26th, and a few slides ensued. Rob also
displayed some shots of the sun taken throu his H-alpha
filter.
Sane terrific aurora slides were displayed by Frank
Roy. All shots were taken on a tripod and averaged about
30 seconds in exposure time. Of particular interest was
the variety of colours in this particular aurora display,
which took place in late February.
Philip Forsythe was up next with th e planet review.
He stressed that now is the time to observe the planets,
since most of them can be found in one night, and they will
be in opposition soon. Philip also showed some slides of
the planets and pointed out some surface details that
should be visible through medium-sized scopes. Some
handouts were available after the meeting.
Variable star coordinator Brian Burke told the group
of a graze expedition organized for the end of the month.
-1-The star in question is of 8th magnitude and will be grazed
by a bright part of the moon's limb. More information can
be found in the March issue of Astronotes.
Fred Lossing passed on an interesting article to the
group which dealt with the upcoming planetary alignment.
An article by Doug Welch criticized some of the
unscientific predictions that warned of ill tidings for
planet earth. Doug's article stressed that such wild
speculation is unfounded; his own calculations show no
significant effects on our planet.
Rolf Meier gave a talk illustrated with slides of his
recent visit to Arizona. Included in the presentation were
slides of David Levy's telescope garden, some shots of the
Arizona sky, Meteor Crater, and the Grand Canyon.
Rob McCallum was up next with some slides of the
"Quiet Site", located near South March, along the Ottawa
River. Rob pointed out that the use of the site in the
future is a good idea, seeing as how gasoline prices are
astronomical, and IRO is about 3 times the distance of the
Quiet Site. Rob hopes to organize a clean-up crew for the
spring and have some star nights scheduled for this summer.
Rolf adjourned the meeting at 9:48 pm.
* * *
OBSERVER'S GROUP MEETING - APRIL 2 Dave Fedosiewich
Chairman Rolf Meier opened the meeting at 8:22 pm with
43 people in attendance, 33 of whan were members. Rolf
informed key holders to IRO that the new keys are now
available at the usual $20 fee. Back by popular demand is
the Observer's Manual, still on sale at the usual low $6.
Vice-Chairman Rob McCallum took over the chair with
news of the upcoming General Assembly. Rob would like to
hear from anyone putting together a display, so here's your
chance, folks! Also, as the Quiet Site is to be reopened
real soon, volunteers are needed to help in a small cleanup
of the area (it's really a lot of fun).
Astrophotography man Frank Roy gave us a strong dose
of Ottawa city lights and the like as he explained the
effects of night lights on astrophotographs. He also
showed the group some slides of Orion, Corona Borealis, and
others, taken under sky fog conditions.
Solar coordinator Rob Dick gave us a rundown on recent
solar activity, correlating data from observations at
-2-visual, H-alpha, and radio wavelengths. Colour slides of
the sun showed some interesting sunspot groups and
prominences easily visible on the limb, due to improvements
in film contrast.
Brian Burke gave us details of the interesting but
disastrous (what an understatement) grazing expedition.
These guys have the habit of bringing along a good deal of
sour luck, including faulty tape recorders that accelerate
the normal playback of speech, dead car batteries, a couple
of mean-looking dogs, to name but a few. Brian assures us
there's better grazes ahead, including one on April 30th.
Interested people were to meet fully equipped at NRC around
8:45 pm. Lotsa luck.
Gary Susick explained the effects of increased
aperture on the results of astrophtotgraphy at the prime
focus. He also brought in sane eyepieces recently
purchased from abroad. He finished off with some slides
courtesy of Celestron International, showing various deep
sky objects, taken with various aperture telescopes.
Meteor coordinator Dave Lauzon was up to brief us
about the Lyrid meteor shower due on April 22nd . This
shower takes place during a new moon so the rate should be
in the order of 15 per hour.
Up with news about the planets was Philip Forsythe.
Jupiter is at opposition on the 6th and Saturn on the 9th.
The rings are tilted at about 11.7°, and should be of
interest as the angle increases throughout the spring.
Venus is also visible with an elongation of 17° from the
sun.
Brian was up once more, this time as variable star
coordinator. Brian gave us a brief description of the
types of variables and their periods. He explained how
different types of variables had different light curves,
and how the brightness could be observed with binoculars
from the city.
Rolf adjourned the meeting at 10:06 pm.
* * *
QUIET SITE
Following are the names of people with access to the
site:
Robert Dick....
Robert McCallum
Rolf Meier....
Dave Lauzon....
Frank Roy.....
224-5583
729-9977
820-5784
745-7962
820-0874
-3-RECENT SOLAR ACTIVITY Ro b Dick
A detailed report of a February aurora was submitted
to me in the last month. Malcom Lambourne reported a very
bright aurora on the evening of Monday, February 22, 1982,
between 19:40 and 20:40 EST. Several aspects of this
display are representative of displays observed over the
past year.
He reported seeing colour several times extending
from a northern homogeneous arc (HA) up to the zenith.
This indicates how bright this aurora was. The activity of
the display built up and faded several times. In this case
the first "performance” faded after 8 minutes to be
followed by another "act". The second flash of activity
produced three curtains 5° above the northern horizon with
"flames" streaking upwards. This time the visible red
colour was limited to the north with the zenith
predominantly a neutral grey.
At times the aurora was seen to "pulsate". These
pulsating clouds or patches can vary quite quickly. Malcom
estimated that they cycled 2 to 3 times per second or so.
They can brighten suddenly within 1/2 second.
The familiar curtains can sway and vary in brightness
rapidly as well. Between 20:10 and 20:15 EST he reports a
curtain between Cassiopeia and Auriga flashing and rippling
2 to 3 times per second.
The aurora was particularly extensive, covering 3/4 of
the sky at about 20:33. Observations were terminated at
20:40 due to cold.
Preceding that date, the sun was at a moderately
enhanced level of activity, with a burst at radio
wavelengths about 30 hours before (see figure).
Three other aurorae were reported during March and
April (March 14/15, April 2/3, and April 10/11).
The accompanying figure shows the variations in solar
emissions at 435 MHz expressed in Solar Flux Units, where
1 SFU = 10-22w/m2Hz. The "x" above the horizontal axis
indicates a reported aurora, and the ticks and dashes
indicate when black-and-white and colour photographs were
taken in H-alpha light.
These observations, which have been published in
Astronotes for the past year are continuing to show a
variation with a period of about 78 days, or 3 times 26
days. It is interesting to note that the siderial rotation
period of the sun is 25 days at the equator.
On April 19th a major flare was recorded by Ken
Tapping when the sun itself was well off the meridian at
15:00 EST. The burst lasted for more than 15 minutes. On
-4-April 23rd, W WV reported that the solar activity was low.
However, at 10 cm wavelengths, the solar flux was 180 SFU
and magnetic storm warnings were broadcast. These should
be observed as aurora on April 24 and 25. Ken's flare
dosen't seem to be associated with this increased activity
since it occured 4 days before this annoucement. Emissions
from his flare will have already passed the earth at this
writing.
Near the centre of the solar disc is a large complex
group of sunspots. At 80 power the region is peppered with
tiny spots lacking penumbra. These are called pores. At
times of poor seeing many of these are blurred, resembling
bands of penumbra. Photographs of these will be shown at
the May Observer's Group meeting, film development
permitting.
* * *
-5-President:
K. F. Tapping
593-6060
684-1186
ROYAL ASTRONOMICAL SOCIETY OF CANADA
Ottawa Centre
Lecture Meeting
Thursday, May 20th, 1982
Secretary:
C.R. Molson
225-3082
996-0845
Speaker: Dr. D. Smellie
Topic: The Solar Corona
After many years of study, the solar corona remains a poorly
understood feature of the sun. Its high temperature of
millions of degrees, as inferred from spectral and radio
observations, has still not been explained. In order to
account for the heating of the corona, energy transport by
acoustic and hydromagnetic waves has been proposed.
In this talk, the main aspects of the corona will be described
and current theories discussed.
The meeting will be held in the Auditorium of the National Research Council,
100 Sussex Drive. The starting time is 8:15 p.m.
Admission is free, and an invitation is extended to members and non-members.IT'S PLUTO TIME AGAIN Cave Fedosiewich
If life's been dull lately, and you'd like a real
challenge, then it's time to find Pluto. The smallest and
second most distant planet is coming to opposition this
month and will be at its brightest at magnitude 13.7.
Here's how to go about finding it.
The first thing to do is to get a copy of its path on
a large scale atlas. An excellent map is provided in the
Observer's Handbook and is really all you need. Next,
you'll need a large telescope (8-inch or larger) with
accurate alignment to the pole so that the setting cirlces
will be accurate enough.
Once your scope is pointed in the right direction,
choose an eyepiece that will yield low power with a wide
field, and look for a familiar pattern that you've noticed
on the finder chart. Any pattern within a few degrees is
fine, since you can star-hop to the location that Pluto is
expected to be at.
Once you have the right field, progress to a higher
power eyepiece with a smaller field, but not so high as to
lose the orientation. You will now find that Pluto is at
the location predicted by the curve on the finder chart.
The planet should appear fairly dim but easily
distinguishable at 100x in IRO's 16-inch telescope under
dark skies.
well, that's it, right?
No, not quite. Check on the planet a few days later
to make sure that it is indeed Pluto (You may doubt
yourself on your first attempt). Sure enough, the planet
will have moved in relation to the backgraound stars.
A neat idea would be to find Pluto photographically,
as shown in the accompanying drawings. Take exposures of
the "suspected" field a few days apart (3 days is plenty)
using prime focus techniques. Sure enough, when you
develop your exposures, one of the "stars" will appear to
have moved. Now you have a "before" and "after"
situation, not unlike what you see in shampoo commercials.
Let me know if you observe Pluto, and I'd like to see
your results for comparison. I'd also like to see some
discription of your observations in Astronotes, or you
could give a talk at the next Observer's Group meeting. If
you have any questions, give me a call at 731-7583.
* * *
-6-b e f o r e A FTER
THE COMET REPORT Dave Fedosiewich
There are more questions than there are answers on
many topics concerning the characteristics of comets.
And if you prefer observing them, our first periodic
comet of the year comes into reach of amateur telescopes
this month. Comet Grigg-Skjellerup should be visible in
early May in the evening sky at magnitude 11 to 12
throughout the month. A detailed ephemeris is available in
the Observer's Handbook. If you observe the comet, sketch
it and give me a copy for publication in Astronotes. Or
better, write about it yourself or give a talk about your
observations at an upcoming Observer's Group meeting.
* * *
Articles for the June issue of Astronotes are due by
May 21s t .
* * *
-7-FIG. 1 PERTURBATIONS FROM
JU PITER
JUNE IS INSTRUMENT NIGHT Rob McCallum
Those members who have been coming to meetings for
some time may remember that the June Observer's Group
meeting was "Instrument Night". Members would bring in
assorted pieces of astronomical equipment, ranging from
telescopes to an electronic bug-repelling device, for
display.
Rolf and I have decided to revive the idea, as it was
quite popular. Members are invited to bring in any
equipment they would like others to see to the June 4th
Observer's Group meeting. We'll make the meeting a little
shorter so everyone will have a chance to look at
everything.
* * *
-8-THE PORTABILITY OF TELESCOPES Rolf Meier
When Lord Rosse built his 72-inch reflector, he had to
go no further than his own back yard for dark skies.
Little did he know that amateur astronomers of the future
would have to deal with the problem caused by city lights.
Nebular filters aside, the only way to overcane light
pollution is to travel far away from the city.
In recent years, the trend has been towards large
aperture telescopes. About 15 years ago, a 4-inch
refractor or 6-inch reflector were good-sized amateur
instruments. The two companies responsible for increased
light-gathering ability among amateurs are Celestron and
Coulter, the former with a good marketing program, the
latter with low prices.
Celestron's answer to the portability problem is the
folded light path characteristic of the Schmidt-Cassegrain
design. An 8-inch f/10 telescope has a tube about a
quarter the length of a comparable Newtonian. Such a
telescope fits neatly into even the most compact of m o d e m
cars. The era of huge trunks has been replaced with that
of hatchbacks and fold-down seats.
But there are still amateurs who prefer to build their
own telescopes. The economies of size are now greater than
they were 15 years ago. Then you could build a 6-inch
telescope for much less than a ready-made one would cost.
Today, through the Coulter Optical Company, and a man named
John Dobson, it makes sense to build a 10-inch, 13-inch, or
even 17 1/2-inch telescope at a reasonable cost. This is
mainly due to the concept of thin mirror blanks.
A typical thin mirror is about one half to one third
the thickness of the old style blanks which had a 6-to-1
diameter to thickness ratio. This results in a
considerable saving in expensive pyrex (or even plate)
glass, and therefore a much lower cost. Even a completely
figured and aluminized mirror can be had at reasonable
cost.
Since the mirror is thinner, it is much lighter, and
therefore a less robust mounting is required. This results
in a further saving of weight, and hence increased
portability, which is our goal.
Several years ago, John Dobson perfected an
alt-azimuth style of mounting which combined portability
(compactness) and stability. When combined with a
large-diameter thin mirror, it enables the m o d e m amateur
to do some terrific observing under dark skies.
Since the mirror is thin, care is required in its
support. This is where the alt-azimuth design canes in.
-9-The Dobsonian design results in a compact, portable
telescope.
Its design allows for the minimum stress to he placed on
the mirror as the telescope is pointed at various angles.
I have recently put into operation a 17 1/2-inch
telescope, which uses a mirror from Coulter. A comparison
with the 16-inch at IRO proved to be quite favourable. At
f/4.5 it is more sensitive to optical alignment, however,
which is complicated by the transport process. This
problem will surely be solved, though.
For more information on large aperture portable
telescopes, see the Coulter ad in Sky and Telescope, and
send away for the booklet on Dobsonian reflectors, also
advertised in S & T.
-10-ASTRO NOTES
c / o Herzberg Institute of Astrophysics
National Research Council of Canada
100 Sussex Drive
Ottawa Canada
K 1A 0R6
MS. ROSEMARY FREEMAN CAST
NATIONAL SECRETARY
THE ROYAL ASTRON. SOC. OF CAN.
124 MERTON STREET
TORONTO, ONTARIO M4 S 2 Z