WADHURST ASTRONOMICAL SOCIETY

NEWSLETTER FEBRUARY 2002

INDEX: MEETINGS, OTHER NEWS, CONTACTS,

MEETINGS

LAST MONTH

The last meeting of the Society was held on February 13th at Uplands. The speaker was our very own Ian King who gave a talk on the subject of Astrophotography. The talk was illustrated throughout with many of Ian’s slides, which were again absolutely stunning. Ian started out with the basics of Astrophotography starting with untracked photos taken using a normal 35mm SLR camera. From here the talk led onto using telephoto lenses and starting to track the camera across the sky during exposure. This then led onto using a telescope at Prime Focus as you would a large telephoto lens. Ian then went into more complex ideas such as guiding techniques using a telescope to guide a telephoto lens. This obviously led into the area of what is needed to take good guided photographs. Ian pointed out that probably the most important piece of equipment is the actual mount of the telescope. This is followed by the Optics of the scope and then into areas such as the type of film. Ian quickly led us through the various designs of telescope discussing the various pros and cons of each.

After a short break for refreshments Ian continued the talk into the area of which film should be used. Various types were discussed including Ektachrome P1600, Kodak Supra 400 and Fuji Provia 400R. There are differences between all the films, some displaying better towards the Blue end of the spectrum and some towards the Red. It obviously depends to a great degree on what is actually being photographed as to which to use. Ian did mention that Elitechrome E200 is probably one of the best for general astrophotography. There are of course things that can be done to improve a film such as hypering and Ian went into the pros and Mainly cons! Ian then went on with the subject of guiding a telescope, discussing both manual and autoguiding.

Of course the main problems with manual guiding are the fact that it is very time consuming and also needs to be done accurately. Ian himself uses a ST4 Santa Barbara Autoguider and the results speak for themselves. One of the pitfalls that was mentioned was to make sure that the camera is either entirely manual or remove the battery, as even the light from an LED can ruin a photo. Ian concluded the talk with a quick look at CCD’s, which have their own pros and cons. He finished by advising that anybody looking to start out in the field of astrophotography started out simply with a 35mm camera and 50mm lens before progressing up the scale.

There were a number of items that were bought up during the last part of the evening. As usual I have put these under separate headings later in the Newsletter.

NEXT MONTH

The next meeting of the society is due to be held on Wednesday March 13th, the venue is the drama studio at Uplands as usual and the meeting will start at 7.30 pm. The speaker at this months meeting is Konrad Malin-Smith who will be giving us a talk on the subject of Supernovae. I am sure many members will remember Konrad from his previous talks to us, as he has spoken on the subjects of Binary Stars and La Palma Observatory. Remembering those talks, I have every confidence in saying that this talk should be entertaining to all members. There will also be a raffle at this meeting, this is following a suggestion made at the January meeting.

GO TO INDEX

OTHER NEWS

TREASURERS REPORT

The treasurer is pleased to announce that 40 of our 52 members had renewed their subs by the end of February. The Society having completed the first three laps along the current membership year. We understand that Ian looks daily to see if any of the dozen cheques to come in have made it through the post.

Attendance at the winter meetings (including the AGM!!) remained high. It is hoped that this indicates satisfaction with the quality of speakers and their material. If there are any particular aspects of Astronomy or kindred subjects that you would like to have covered please contact Tim, or any other member of the committee. We will endeavour to find the appropriate speakers.

It was suggested at the February meeting that we might consider running a monthly raffle. This could add to the entertainment of the evening with a modest benefit towards our fundraising. The prizes for the first raffle, to be organised by Valerie, will be a constellation umbrella and a bottle of something of the Chairman’s choosing.

FUNDRAISING

The subject of fundraising was again raised at the last meeting. The society has already been booked into Speldhurst Village Fete on June 22nd. It is anticipated that this will mainly be a display of telescopes and information event, although if anyone has any good fundraising ideas for the day please come forward!

Fundraising is vital to the society and those members present at the meeting had a good discussion on various ideas. The two main ideas are should we raise money from outside or inside the society? Various ideas were suggested such as a raffle at meetings (See above!), a sponsored walk and a barn dance. It was also suggested that the society barbeque could be used as a fundraing event. The other suggestion was that we could raise more money by raising the subscription rate. It is obvious that this matter needs to be looked at in greater detail, but if anyone has any comments or ideas that they would like to put forward please speak to any committee member. This subject is important to all members in that the money raised goes towards your society! It was pointed out by the treasurer that although at present it looks as though the society is in a good financial state this could change quite rapidly depending on the charges of our speakers.

SOCIETY TELESCOPE

The society telescope is now available for hire and is in fact at this moment in the hands of our first hirers. I hope that we will hear more about the first month of use at the next meeting. If anybody wishes to put his or her name down for the use of the telescope for a month please contact Peter Prince (01892 836284). Please remember that there is a small charge of £5 per month for the loan of the telescope and also a refundable deposit of £30.

COMPUTER SOCIETY

Alex Hunt made the following appeal at the January meeting.

I am a committee member of the Local (Sussex) British Computer Society. We hold 6 weekly meetings at the Department of Engineering at the University of Sussex, Falmer. We are looking for other societies that are interested in participating in joint meetings with us. I have been thinking about this for sometime now and have concluded that there are many aspects of Astronomy that require the use of computers. From image capture and image processing to computer controlled telescopes and statistical analysis of data. If you can suggest a subject and a speaker, I can arrange a date, lecture theatre, advertising and a buffet meal for a joint meeting later this year or early next year (we work a year ahead).

If anybody has any ideas or suggestions on this matter please see Alex at a meeting or contact the Editor.

CONSTELLATION OF THE MONTH

The following is a full copy of the notes on the constellation of Canis Major that Sean used at the last meeting;

The constellation Canis Major does resembles the shape of a dog, but it could have easily been named after a variety of other four-legged animals. From our viewpoint it looks like a dog jumping on its hind legs. There doesn’t appear to be any well known myths or legends specifically relating to Canis Major, but is usually mentioned as one of Orions hunting dogs. The constellation is best known for containing Sirius, the brightest star in the night sky.

Sirius can be found by using the three stars of Orions Belt as pointers. Follow an imaginary line downwards though the three stars and Sirius will be approximately 21° away. But how can 21° be easily measured? By comparing various parts of the hand held at arm’s length, against the sky, one can determine an approximate angular distance. For small angular distances the index finger can be used. It’s width is about 1°, from the tip to the first knuckle is about 3°, from this knuckle to the next is about 4°, and from this to the last knuckle is about 6°. Across all the knuckles of a clenched fist is about 10°, and finally from thumb tip to the tip of the little finger of the stretched open hand is about 18°. However Sirius is so bright it will almost jump out of the sky and hit you. Sirius is also known as the Dog Star. Roughly 1000 years ago it rose shortly before the sun at the start of August and heralded the "dog days of August". The hot muggy weather was said to be caused by the light of Sirius combining with the light of the Sun! Go further back in time to 3000 B.C., and Sirius rose just before the sun in early summer. The name Sirius is in fact derived from Greek meaning scorching. The ancient Egyptians used the predawn rising of Sirius (called the heliacal rising) to predict the flooding of the River Nile.

NAMED STARS

Designation Common Name Pronunciation Ra Dec Mag
Alpha Cma Sirius SEAR-ee-us 06h 45m 15s -16° 43' 14" -1.6
Beta Cma Mirzam MIR-zam 06h 45m 15s -17° 57' 34" 2.0
Delta Cma Wezen WAY-sen 07h 08m 29s -26° 23' 56" 2.0
Epsilon Cma Adhara ah-DAY-rah 06h 58m 43s -28° 58' 39" 1.6
Zeta Cma Furud FEU-rud 06h 20m 24s -30° 04' 03" 3.1
Eta Cma Aludra ah-LUD-ra 07h 24m 11s 29° 18' 34" 2.4

Sirius is only 8.5 light years away, making it our sixth closest star. It has a binary companion named Sirius B or The Pup. At Mag 8.5 it should easily been seen with binoculars, but its close proximity to Sirius of only 4.6" means that it is swamped by the light of Sirius shining 10,000 times brighter, making it virtually undetectable. Splitting this pair is a challenge even for large telescopes. Sirius B was discovered in 1862 and takes 50 years to orbit Sirius. Its claim to fame is that it was the first star to be recognised as a White Dwarf. It has a similar mass to the Sun, but with a diameter of only 0.022 of the Sun’s. At this density a tablespoon of matter would weigh over a ton!

Deep Sky Objects

M-41 – The little Beehive. Large and splashy, this fine open cluster is easily seen as a hazy patch to the naked eye, four degrees south of Sirius and almost half a degree wide. A pair of equally bright red stars near its center dominates the cluster, and about 60-70 stars can be seen at low power, many in curving chains radiating from the center. About 325 B.C. Aristotle noted M-41 as one of the mysterious "cloudy spots" then known in the sky. However, the first telescopic discovery was by Hodierna sometime before 1654. He thought that it was a “nebula”. Flamsteed rediscovered the cluster on Feb. 16th, 1702, and again by Le Gentil in 1749.

NGC 2362.  This cluster surrounds Mag 4.3 star Tau Canis Majoris, and is simply known as The Tau Canis Majoris Cluster. This is a small compact cluster about 6' in diameter. It contains about 60 stars, most of them being moderate in brightness. This is one of the youngest star clusters, perhaps only 50 million years old.

NGC 2354. This is relatively large, at 20' in diameter, and can be found about halfway between Tau CMa and delta CMa. It’s round, and composed of relatively bright stars with a sprinkling of fainter stars.

NGC 2359 The Duck Head NebulaThis is a large and faint diffuse nebula about 10' in diameter, best seen at low powers. It is composed of an arching segment intersected at almost right angles by a straighter component, resembling a duck's head and bill. The nebula is caused by mass loss from the Wolf Rayet star HD56925. (Wolf Rayet stars have spectrums with bright emission lines rather than dark absorption lines. They are very hot with a surface temperature of up to 50,000K and have a luminosity of up to 1 million times that of the Sun. Their strong solar wind can expel the equivalent of 3 solar masses every million years.)

An image of NGC 2359 by Nik Szymanek, and our very own Ian King can be found here.

NGC 2360 This is a large dense open cluster, 12-15' in diameter, with about 75 stars well concentrated to the center. It is visible in the viewfinder and impressive through the telescope.

IC2177, Known as the Seagull Nebula, is a large 120 x 40 arc minute area of emission nebulosity located on the border between Monoceros and Canis Major, about 7.5 degrees northeast of Sirius.

The brightest portion is the "head" of the bird, NGC 2327, measuring some 19 x 17 arc minutes, surrounding an 8th magnitude star, and nearly bisected by an interesting dark lane that stretches from the star eastward, and also including some blue reflection nebulosity.  Several open clusters are also involved in this area of nebulosity, the most prominent being NGC 2335, located on the northern "wing" of the figure of the Seagull Nebula

ADS 5951 This is a fine double star composed of a Mag 4.8 yellow-orange star and a Mag 6.8 pale blue star. This is similar to the famous Albireo in Cygnus. It's about 0.7° north of Tau CMa and is worth checking out!

Selected Deep Sky Data

Designation Common Name Ra Dec Mag Size
M41 The Little Beehive 6h 46m 6s -20° 44' 17 4.5 38'
NGC2354   7h 14m 24 -25° 44' 21 6.5 20'
NGC2362 Tau CMa Cluster 7h 18m 54s -24° 57' 22" 4.1 8'
NGC2359 The Duck Head Nebula 7h 18m 42s -13° 12' 20"   8'
NGC2360   7h 17m 54s -15° 37' 20" 7.2 13'
IC2177 Seagull Nebula 7h 05m 12s -10° 42' 18"   120' x 40'
ADS5951   7h 16m 10s -23° 19' 4.8, 6.8 27" (separation)

Good web links

The Hawaiian Astronomical Society has some very good astronomy maps generated by TheSky software as well as some excellent general information. Their website can be found here

A selection of images of open clusters in Canis Majoris can be found here

Good pictures of Canis Major and IC2117 – The Seagull Nebula can be found here

A list of bright deep sky objects can be found  here

A detailed explanation of Wolf Rayet stars can be found here

GO TO INDEX

CONTACTS

Chairman: Murray R. Barber 01892 654618 murray.barber@virgin.net

Secretary: Tim Bance 01732 832745 timbance@hotmail.com

Treasurer: Ian Reeves 01892 784255

Editor: Peter Bamblett 01732 368656 pbamblett@hotmail.com

Web site: Rob Cray rob@arcray.net

Publicity: Michael Harte 01892 783292 michael@greenman.demon.co.uk

Dir. of Obs.: Sean Tampsett 01892 667092 sean_tampsett@hotmail.com

Librarian: Joan Grace 01892 783721

Custodian of Equipment: Peter Prince 01892 836284

GO TO INDEX