WADHURST ASTRONOMICAL SOCIETY
The last meeting
of the society was held on 11 September, and the speaker
was Owen Brazell on the subject of “Planetary Nebulae”.
Owen’s talk was split into three separate parts, The
History of Observations, Current Understanding and How
and Why we might observe. The first Planetary Nebulae
were discovered by Messier
when he was compiling his list of objects that could
be mistaken as comets. This was followed by Herschel
who did an all sky survey. At first they were thought
to be stars to far away to resolve although there were
a number of Planetary Nebulae that caused problems to
this theory. By the late 1800’s Herschel's
catalogue was out of date and Dryer started the
New General Catalogue. It was the use of the spectrograph
that proved that Planetary Nebulae were Gas rather than
stars. The first spectrographs showed what was thought
to be a new element that was named Nebulium.
It was much later that this was found to be OIII (Oxygen
with 2 electrons removed). The NGC was added to with
the NGC2 index but many items in this index were duplicates.
There has been much debate about what a Planetary Nebula
actually is and at one time the definition was that
a Planetary Nebula was a Planetary Nebula if a) nobody
objects and b) was in a catalogue of Planetary Nebulae!
The first catalogue
of Planetary Nebulae only was compiled in 1967 and currently
the UK Schmidt is looking for Planetary Nebulae, it
is therefore expected that the number known may double
in future years. The talk then continued with
a slide show of a number of Planetary
Any star with a mass of between 0.9 and 6 solar masses may end its life as a Planetary Nebula. After many years on the Main sequence a star will run out of Hydrogen in its core. At this point the star will shrink causing the temperature to increase that will allow Hydrogen burning in the shell of the star. The star will continue to expand and contract until the star's core is exposed: it is the matter thrown off during this stage of a star's life cycle that creates a Planetary Nebula. The star will go on to become a white dwarf. What actually causes the shape of the Planetary Nebula is unknown although theories include:
Owen continued with some reasons as to why we should
be interested in Planetary Nebulae. These include the
fact that as they are created from a star they allow
us to study the internal make up of stars and they can
be used as standard candles for measuring distance.
Also of interest is the fact that there are only 4 Planetary
Nebulae known to be in globular clusters, although there
should be more.
After a short break Owen continued the talk with some details on the observation of Planetary Nebulae. Because they are relatively bright, they can be observed using high power, they also show colour. Many of the bright Planetary Nebulae are well catalogued; there are 4 in the Messier list, 76 in the NGC and 13 in the Caldwell list. There are a number of Planetary Nebula only catalogues available such as the Perek/KohoutekAbell and Minkowski lists, details are also available from the Webb society. For charts Uranometria is recommended, as are the major computer programs such as Skymap and The Sky.
There are of course nebula filters available and these were discussed in detail including why they are so expensive. As a guide Owen suggested the UHC as a good 1st buy followed by an OIII for faint nebulas. The H beta filter only works on about 10 objects! All filters should be used at low powers; at high power the filter will have less effect.
Owen finished the talk with a number of challenges that observers might like to take on. These included M15, M22, Pa16, NGC6441, NGC6543, NGC7008 and NGC7009.
The next meeting is on 9 October. The venue is Uplands Drama studio and the meeting starts at 19:30. The speaker this month is Pam Spence. Long-term members may remember Pam visited the society 2 years ago and was a most entertaining speaker.
There is due to be a committee meeting of the society during the first week of October. Hopefully all members have received advance notice of the subjects to be discussed. A full report of the meeting will be given in the next newsletter.
On March 12 2003 the Sussex branch of the British Computer Society is holding a meeting with a talk to be given by Prof. M. P. Gough of the Space Science Centre. The title of the talk is Intelligent Space Instruments. The meeting will take place in Engineering Building 1, University of Sussex, Falmer, Brighton at 7.15 for 7.30 p.m. Unless things have changed by then, the evening in question is the second Wednesday of March and so it is possible this will fall on a WAS meeting. If any member is interested in attending the meeting please contact either Tim or Alex Hunt (email@example.com). If enough members are interested it may be worthwhile for the Society to organise some transport.
The society will start to have a regular monthly observing session during the later part of the year. It has been suggested that those members who are interested meet in the Crow & Gate Pub in Crowborough, at 8 pm and then go onto Ashdown Forest for an observing session (weather permitting!). The suggest dates are: October 4, November 1 and December 6. These are all for Fridays and are the nearest to the New Moon
The annual WAS Star-B-Q took place on the evening of 31 August 2002. There were some photos of the event at the last meeting of the society and the reports of the evening were all very favourable. Once again thanks to the hosts, Michael Harte and his wife for making the event another success.
The society is looking for a place to hold an exhibition in 2003. Proposals so far are Paddock Wood and Crowborough. If any member has any contacts or suggestions as to venues for an exhibition next year please speak to Ian Reeves (01892 784255)
The committee meeting
was held on the evening of September 30 at the Abergavenny
Arms, Frant. There were a number of items discussed:
the main one affecting all members was the proposed
change to the date of the monthly meeting. There are
unfortunately a number of members who are unable to
attend the meeting on the present night. After discussion
it was agreed that the best change would be from the
second Wednesday to the third Wednesday of each month.
If anybody has any objections to this proposed change
please contact Tim (01732 832745) as soon as possible.
If no objections are raised the change will take effect from the January meeting 2003.
It was also pointed out that the meetings have over the course of time managed to gain a later starting time. The society has use of the Drama studio from 7.15 to 10.00 pm and so in future the doors will open at 7.15 and the meetings will start at 7.30 prompt.
As mentioned above a full report of the meeting will appear in next month's Newsletter.
Chairman: Murray R. Barber 01892 654618 firstname.lastname@example.org
Secretary: Tim Bance 01732 832745 email@example.com
Treasurer: Ian Reeves 01892 784255
Editor: Peter Bamblett 01732 368656 firstname.lastname@example.org
Michael Harte 01892 783292 email@example.com
Society Website www.wadhurst.info/was
Dir. of Obs.: Sean Tampsett 01892 667092 firstname.lastname@example.org
Librarian: Joan Grace 01892 783721
Custodian of Equipment: Peter Prince 01892 836284
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