MIRA 19
December 1987



CAVENDISH


CAVENDISH
54°W 25°S

CAVENDISH   A formation 32 miles in diameter.  Its walls are of fair height, attaining 7,000 feet in places, but are disturbed by smaller craters.
Atmospheric turbulence made the drawing hard, with the image jumping all over the place.  However clear skies helped to define the crater.
A superb terrace is winding along the west wall, narrowing towards the north wall.  The north wall has a fine dark terrace, which appears to descend from the northern rampart, in the eastern rampart is a prominent craterlet, having a very bright eastern wall, this craterlet looked fairly deep.
Intruding into the S/W wall is E craterlet, this distinctive craterlet also looked deep, there was a black recession to its west wall.
The floor of Cavendish showed a few hills, one being bright is seen adjacent to the black shadow of the east wall, this had a darkish shadow; one low hill is seen on the N/W floor, and a rather odd curving shadow is extending away from E craterlet on the S/W floor.
A long depression is adjacent to the east wall, it appeared to start at the base of A craterlet.


DATE              31st May 1985
TIME               21h 45m - 22h 20m
MOON             12 Days
CONDITIONS   Slight wind, clear, atmos turb, much quivering of image
INSTRUMENT  102mm OG x186
LOCATION      Southam, Warwickshire
OBSERVER     Angela Turner






MIRA THE VARIABLE STAR

Some time during late December or early January, Mira the red variable star in Cetus, will be at maximum once again.
Mira is normally visible with the naked eye as a star of around the 2nd magnitude for only 18 weeks out of it's 47 week period.  The magnitudes of successive maximum are by no means consistent, on one occasion in 1779 the star attained the first magnitude but in 1925 and 1935 the star hardly became visible to the naked eye.  At minima Mira can fall to the 8th or even the 10th magnitude so telescopes are required to follow the star through a complete cycle, in addition to it's varying magnitude, it's period between successive maximum is by no means constant either, as it can vary between 320 to 370 days with an average of about 331 days, and even today after extensive observations of Mira, there seems to be no way of predicting the date of the next minima or maxima to an accuracy of about 15 to 20 days.
What causes the star to vary in brightnesses due to the fact the star expands and contract some 1400 times in radius. At maxima the diameter of Mira is over 450 million kilometres. The surface temperature varies between about 2600k at maximum down to about 1900k at minimum.
Mira first came to the attention of David Fabricius on the 13th August 1596 and also observed seven years later by Johann Bayer, but it finally became established by Phocylides Holwarda that the star brightens and fades in a semi regular manner and referred to as a long period variable star, Holwarda in fact christened the star Mira.
Mira, like most long period variable stars are characterised by their red colour, but Mira is by no means as red as many stars of it's class.



If you take the trouble to see Mira you will also perceive a 8th. magnitude companion which lies within 2' of Mira, some sources say that the companion can only be seen around minimum of Mira, so give it a go!







Unknown Worlds   Part Three
By Rob Moseley

In fairness, Challis had not been entirely lax in his search.  He had charted over 3,000 stars. Nevertheless, both he and Airy had their heads on the block.  Shortly afterwards they were called to explain their actions at a meeting of the Royal Astronomical Society. There followed a rather distasteful argument across the Channel as to the true discoverer.  Thankfully, neither Leverrier nor Adams took part and they carried mutual respect and admiration to their graves.  There was also the usual dispute over the naming of the new planet.  Leverrier, the complete mathematical astronomer who never ever "bothered to look at his planet through a telescope, said he would only agree to the name "Leverrier" if Uranus were renamed "Herschel".  Galle suggested "Janus".  Finally the mythical Neptune was agreed.
We still know precious little about Neptune. Its sheer distance from the Earth defeats us.  Thus the Voyager 2 rendezvous in 1989 is awaited with keen interest.  It is likely that there is little physical difference between Neptune and Uranus.  They both have extremely high albedos, the highest of all the planets at around 70%. Neptune's diameter is in the order of 27,000 miles, 2,000 miles less than Uranus.  Its day is given as 15 hours long, but this is little more than a guess.  Its year is equal to 165 of ours, in fact it will not return to the point of its discovery until 2011.  Its surface temperature is a mortifying -170°C... and the Neptunian's take 900 times longer than we do to obtain a suntan!
Three weeks after discovery, Lassell, still hobbling about with ankle in plaster, directed his new 24 inch reflector onto the planet.  He observed a tiny star alongside Neptune.  In five days it circled the planet.  It was named Triton and is Neptune's major moon, appearing a glaring magnitude -6.4 to Neptunian lovers.  Lassell was jubilant, for it was confirmation to him that the reflector was superior to the refractor... until three weeks later his discovery was confirmed independently by Bond at Harvard Observatory, using only a 12 inch refractor.  Triton is a large and peculiar world. It is believed to have a methane atmosphere.  Its orbit is so circular that its eccentricity has yet to be determined.  Even stranger still Triton's motion is retrograde, which may be an important clue in solving the enigma that is Pluto.
Pluto was suspected for over 50 years before its discovery in 1950.  Even now many astronomers wonder whether Pluto is a real planet, an escaped satellite of Neptune or the brightest member of an asteroid belt on the very edge of the Solar System.  Many questions still lie unanswered, and we will have no Voyager to answer then for us.  Destined to be discovered on the same day (March 13th) and within 15° of Uranus's discovery position near the bright star Delta Geninorum, the search for the trans-Neptunian planet was essentially a photographic one.
Two camps were involved - the Pickering/Humason team and the Lowell/Tombaugh team.  After years of patient and laborious work Pluto's tiny image fell onto the photographic plate and Clyde Tombaugh was accredited the discoverer, though all the theoretical work and the initial impetus for the project was Lowell's although he was dead before the actual search began. The symbol for the planet, PL, is a tribute to him.  However, no one can deny Tombaugh's claim to fame.  During his 14 year search he had to check an estimated 20,000 planetary suspects and a total of over 30 million star images through the blink microscope - as well as take all the plates!  Milton Humason, it must be recorded, had terrible luck.  When He was searching for Planet P (the Lowell camp called it planet X) at Mt. Wilson in 1920 the image of the planet fell onto a flaw in the photographic plate and was lost.  Pickering considered that Lowell's Planet X was not the same as his Planet P - Pickering's "Pluto" remains to be discovered.
Airy had previously stated that he thought the idea of trying to predict the position of a trans-Uranian planet was untenable due to the sheer difficulty of the celestial mechanics involved - and furthermore he did not believe in the existence of such a planet anyway.  Being empirical men both he and Challis were suspicious of purely theoretical predictions.  Adams went to Greenwich on several occasions to see Airy, but on each visit the autocratic Astronomer Royal was too busy to grant him an audience.  At last he gave up and simply left his calculations for Airy's perusal without any note of explanation.  Had he done so it is possible that Neptune could have been discovered a year earlier.  We must bear in mind that Airy was a frighteningly busy man, and that Adams was a very shy unassuming character.
Airy thought that Adams's calculation was a mere guess - an example.  He took no action until he read Leverrir's announcement and noticed that Adams's position was very close to it.  Half realising his mistake he wrote to Challis instructing him to commence the search immediately.  He also wrote to the eccentric amateur William Lassell in Liverpool, but fate played a hand again - Lassell had to default due to a broken ankle.



Sir George Airy

But it was all too late.  Even though Challis started two months before Galle in Berlin he had no adequate charts to help him and had to commence the laborious task of plotting all the stars and checking each one for movement.  His basic distrust of Adams's calculations came out again when he tragically decided to sweep a huge area 10° by 30° around the predicted position.  Using the great 25 inch Northumberland refractor he slowly looked for the needle in the haystack, once actually remarking to an assistant that one of the stars seemed to show a disc.  Legend has it that on the following evening as he was about to depart for the observatory to check its position he was sidetracked by the offer of a cup of tea by his wife, the sky clouding over in the meantime....  The next night was clear, but for some reason he was unable to observe.  The very next day brought the news of Galle's discovery.
In fact many would argue that Lowell's Planet A remains to be discovered as well, as Pluto's mass is far too small for it to produce the observed perturbations in the orbits of Neptune and Uranus.  It was thought recently that the IRAS (infra-red) satellite had found a far more massive 'body on the edge of the Solar System but the reports turned out to be unrounded.  Pluto is certainly the oddity of the Solar System.  It refuses to fit in with Bode's "Law" or the general arrangement of solid dwarfs and gas giants.  At first it was thought that Pluto had a mass roughly equal to that of the Earth, but its diameter was found to be much smaller and the values have steadily decreased over the years.  This would have meant Pluto's density was a remarkable 10 times that of the Earth.  However recent values give the density as only 1.3 times that of water, so now Pluto is regarded as a cosmic lightweight.  Also the escaped moon of Neptune theory was given a jolt in 1978 when Pluto was found to have a moon of its own, Charon - the Ferryman of the Dead.
This gloomy little world with the lowest albedo of all the planets has a very strange orbit which reinforces the doubt about it being a bona fide planet.  It is inclined at 17° to the ecliptic and thus wanders well away from the Zodiac - at the moment Pluto lies in Virgo but was previously in the constellation of Coma Berenices.  Its eccentricity is also very high.  It is now approaching perihelion, becoming brighter as it does so, and now actually lies closer to the Sun than Neptune.  After perihelion in 1989 it will recede into the gulf of interstellar space to an aphelion of a staggering 4,566m miles.
Are there more unknown worlds beyond Pluto?  This seems highly likely, although detecting them presents a virtually impossible task using conventional photographic techniques, indeed, alter his discovery of Pluto Tombaugh continued his search without success, and concluded that any object brighter than magnitude 16 would have been found.  Perhaps future infra red studies will yield results.  Perhaps it has already been gained in the mountain of data from IRAS as yet unanalysed. but probably our best chance of detecting a dark massive body beyond Pluto will come as the two Voyager craft are monitored on their journey out of the Solar System.  As they depart in different directions any deviation in their courses could give important clues or even pinpoint the source of unaccountable gravitational effects.  We must wait and see.

Further reading
R Baum   "The Planets - some Myths and Realities"
M Grosser "The Discovery of Neptune"
AFO'D Alexander "The Planet Uranus"





Cursory Observing Session
By Bill Turner and Vaughan Cooper

Instrument 6in. Reflector F/6 mag. x60 and x120 Ortho.
Date 28th August 1987
Location Coventry

α Ursa Minor (polaris)
First a quick check of alignment of the finder to the main optical axis of the telescope, all seems to well.
Polaris a star of 2.1 mag. has a 9.0 companion separated by 18"  At x60 magnification I found the secondary very difficult to see perhaps the eye piece wasn't in correct focus for me just a faint suggestion at times of the secondary at approximately the 7 o-clock position as seen through the telescope although Bill could see it with certainty. At x96 however the companion was easily seen and a very wide double.

M 29 Cygnus
A very loose cluster of approximately 8 stars S.W. following γ Cygni with a magnitude of around 8.  So wide was the cluster I wasn't sure at the time if I identified the right group of stars, an easy group for binocular owners as once you've centred γ, M29 should be in the same field of view.
The surprising feature concerning M 29 I couldn't find any details about it in my copy of Webb's Celestial Objects.

M11 Sagitta
Like M 29 a easy object to locate, approximately point the telescope between γ and δ Sagitta and you'll find the object immediately in the centre of the field of view.  The appearance through Bill's telescope at x60 was a very faint diffuse patch of light better seen as Bill suggested in adverted vision.
As M 11 consists of a group of 9th. mag. stars I had expected to see a slight resolution of individual stars when we increased the magnification up to x96 but this wasn't to be in fact M11 became so faint it could only just be made out.

M 57 Lyra
Bill's turn to operate the telescope and in superb style quickly picked up The Ring Nebula.  The expanding gas cloud well seen glowing with a faint bluish light, and even with a quick examination it's quite clear that the circumference of the disk of light is brighter than the inside area.  The central star that blew off part of it's atmosphere that produced the ring effect which we see can only be seen with larger telescopes than Bill's telescope of 6in aperture.

NGC 663
Whilst Bill was trying to find M103 for me, by chance he found a real gem NGC 663.
The field of view through his telescope seemed full of faint stars — a superb sight.

Cloud and a later hour prevented any further observing







Observations of M 103 and NGC 663
and Double Star Obs.
By Vaughan Cooper

Date 25th September 1987
Time 20h to 23h UT
Instruments 6 inch F/10 Reflector and 4 inch F/4 Reflector

The initial aim of tonights programme to seek out M103 and check up on as many doubles I detailed in the September issue of Mira 1987 (No 18).
Further to the unsuccessful attempt on M103 in Cassiopeia on Friday 25th August 1987, I decided to take a more careful look at this star cluster, particularly as it lies just 1° following and slightly north of δ Cass. so it's very easy to find, although we both (Bill and I) over looked it.
Firstly though, what is M103, the description in Norton's Star Atlas and Webb's Celestial Objects, contains the following — a beautiful field 1° f and slightly north of δ, and contains Σ 131 and a red star, other sources I've referred to states M103 is a loose cluster with 60-70 members which were brought to Messier's notice by Mechain, the visual description by J. Herschel as round and rich.
With my 4 inch reflector which is aligned with and used as a finder for my 6 inch telescope I positively identified M103 straight away, as the 4 inch has a good 2½° or so field of view, so once I brought δ into the centre of the field of view, M103 was visible with a power of x16 as a small hazy patch of light, no stars resolved, also visible was NGC 663 quite approachable larger and brighter than M103 (how could Messier or his assistant Mechain have missed it as it lies so close to M103.
With M103 nicely centred in the field of view of the 4 inch, the view through the 6 inch was a little disappointing, only 6 or 7 stars of about the 7th or 8th mag visible in a very loose diamond formation, on wonder Bill and I over looked it several weeks before, the sketch below gives some degree of what visible.
Couldn't resist another look at NGC 663 with my 6 inch but first a quick alignment check to centre it in the field of view of the 4 inch,again like M103 no stars resolved but it seems to have twice the surface area, anyway, through the 6 inch, a very rich circular arrangement of stars of the 9th mag — now thats what I call a star cluster.
Before settling down to double star obs.  I fancied taking advantage of the very clear sky and looked at M33, only seen once before on the 20th October 1984 with 10 x 50mm. binoculars at the Rev Tim Gouldstone star party.  Again with my 4 inch all that was necessary, was to point the instrument in the area of the sky occupied by M33 and very quickly, with a small amount of searching I could, unmistakable see M33 as a large but faint hazy patch of ghostly light.  I noticed that I could obtain a more contrasting image with my 25mm Ortho as against my 40mm Kelner, of course, nothing could be seen of M33 through my 6 inch, as the lowest power eyepiece is still far too great for this object.  Feeling pretty pleased with my quick success on M33 which incidentally is a face on spiral galaxy, a little further away and smaller than Andromeda, I decided to push my instrumentation to the full and go for M74, which is reported to be the most difficult of all Messier objects, lying as a faint 11th, mag. face on galaxy with a surface area of 12 x 12 and approximately only a 6th of the size of M33, but after a great deal of care of searching nothing could be seen, with either my 4 inch or 6 inch reflectors.






Double Star Observations with a 6 inch Reflector

ι  Cass    The primary, a 4.2 mag star easy to see with the naked eye which has two faint companions.  With a x120 mag I could certainly see one of the companions following ι Cass, with a PA of approximately 110°, to see the second companion I had to push the power up to 180 before it would reveal itself, with a PA of 260°

ι  Triangulum   The primary a 5.0 mag star following several degrees behind ι Triangulum.
Easly split with a magnification of x120.  I noticed the primary star was orange and the companion following with a PA of approximately 80°.

γ  And   The primary a 2.2 mag star and the secondary well seen with a power of x60, the companion was following the primary with a PA of approximately 75°.
Interestingly I could see the double very clearly whilst wearing my glasses which corrects the astigmatisam in my eyes, but not at all without.

δ  Persi  The primary a 2.7 magnitude star and the secondary seen wide but faint requiring a x120 eyepiece to see it.  The secondary proceeding with a PA of approx 200°

Being such a clear night investigated on the number of stars visible in the Square of Pegasus, my total for that night only 4, also counted 6 stars in the Pleiades, I found two of them Taygeta and Merope quite difficault to see, refer below to the stars in question.  Do other members who observe have the same difficulty?

According to Hans Vahrenberg, the German amateur astronomer who has produced some superb star atlases mentions that when the Pleiades is near the horizon he finds it easier to resolve the stars, than when on the meridian where the stars seem to be embedded in bright nebulosity.








A letter from Mike Frost
(the keeper of the Surrey Pumas)
in Australia

First a few basics, I haven't noticed water going down the plug in the opposite direction to the northern hemisphere — it seems pretty random, just like in Rugby (did try a quick experiment as we flew over the equator, but it's a bit tricky to get a bowl full of absolutely still water in the sink in the aeroplane loo, especially when there's a queue of passengers outside).  The Moon is the wrong way up and the Sun is in the south at mid day.
The winter is just ending (you couldn't tell the difference between the Aussie winter and the English summer!), so the nights are still pretty long.
In the early evening, the Southern Cross is more or less due south, with alpha and beta Centauri very distinctive above it.  To the west, Scorpio is quite magnificent — really does look like a scorpion, with Antares glowing red at the bottom, and the distinctive 'sting' at the top.  When I first arrived, Saturn was very close to Antares, and of similar magnitude, but it's moving away to the north east, whilst Jupiter dominates the sky to the west.  A few weeks ago you could just catch Canopus in the south before it set, whilst Achernar, dominates a fairly bare patch of sky to the south east.
I've invested in a pair of binoculars (nothing flash, 12 x 40mm of a Russian make) and with them the most impressive deep sky sight is omega Centauri, which is very easy to find from Crux.  The Jewel Box round kappa Crucis was a bit disappointing, I'd expected more colour.  As you go south from Crux, there are all sorts of knots and clusters as you sweep into Carina.  To put it simply, once you get out of Wollongong city and into the country, the Milky Way is just fantastic, particularly Crux and Centaurus, Sagittarius and Scorpio.  Around Sagittarius is of particular interest to me, as the star clouds and nebula obscure the galactic centre, which you might remember me talking about last year.
The super nova?  Ah, well, I hoped you wouldn't mention that.  It's only visible in the early morning, and I've been too lazy to get up and observe it, (this of course includes the Large Magellanic Cloud).  The Small Cloud was a bit of a disappointment very difficult to make out, even in a pretty dark observing conditions — though I think I've seen 47 Tucanae which is just next door.
The members of the local astronomical society are an extremely affable bunch of people, who it's been my pleasure to join.  They have an observatory just the other side of the Illawerrw Range from Wollongong which they have been building for some time now, but haven't got round yet, to putting a telescope in it, or even completing the roof. Not to worry — everyone rolls up in their cars and brings their own telescopes.  The observatory, however is a great place for a bar-b-que, to start the evening off.  There was a touch of fog, early on, but by the time observing started properly, conditions were excellent — as good as you would ever see from most of England, with perhaps some lights from Wollongong to the east and Sydney to the north.
It was a wonderful evening, not very often I have the chance to explore a completely new sky.  All those nebula, clusters and galaxies I've read about in books — omega Centauri was absolutely beautiful through a 10 inch refractor, with imagination you could see the dust lanes in Centaurus A, and the three parts of the Trifid (well that was a bit dubious).  M4 and 47 Tucanae and eta Carinae, not to mention Jupiter and Saturn, all in all a magnificent guided tour through the southern skies.

Mike intends, if he get the opportunity to take some coloured slides of the southern skies for our society archives, an interesting closing footage from Mike whose been told that Ursa Major is just about visible from Sydney, so I hope his successful in taking that photo for us.
Ed VC






Solar Observations

By Vaughan Cooper



BAA SOLAR SECTION

Observer Vaughan Cooper




Date          17th Oct 1987
Time          12h 45m UT
Conditions   A little unsteady
Instrument  6" Reflector x60
Rotation No. 1794

P= +26.2
Bo= +5.7
Lo= 179.7

Notes. 3 Active areas. 21 spots.





COMET BRADFIELD


COMET BRADFIELD
½° field
Observer R Moseley

1987 Oct 28 18.00 UT
12" spec x60
Starlike central condensation. 5 mag.  Coma effect to PA 90° — diameter 2.3'

On 11th August 1987, Comet Hunter, Bill Bradfield discovered yet another comet (his thirteenth) in Hydra.
Currently, in the constellation of Aquila/Sagitta this comet has brightened to mag 5 and can be seen with the naked eye in dark conditions, being well placed for observation around Christmas.  Good binoculars will show quite a long tail and startike 'head'.





Comet Bradfield  .29' field
Observer B Merrikin

1987 Nov 19  18.15 UT
8½" spec x80
Remarks — Very definite starlike nucleus with a wide 'head'.  Tenuous long tail distantly brighter on S edge and darker in centre.