December 1986

Review of the Coventry And Warwickshire Astronomical Society

The monthly meetings have maintained their traditional standard of variety to suit most levels of interest, along with a lively response during question time from the audience. 
A most encouraging sign for the society since we last published a register of members in 1984 as we have doubled the adult and trebled the junior membership so please keep it up, - (I wonder how much of this has been attributed to a certain comet that has created all the interest). 
The observatory has been in regular use on Thursday evenings by Rob to assist the odd visitor to view the heavens, also he's continued to study the surface of the Moon and will shortly embark upon another programme of measuring the position angle and separation of double stars with a micrometer attached to the 6 1/2"in. Cooke telescope. 
Although the observatory was completely decorated, by a few willing hands of the committee and society members, during their spare time and many thanks for your efforts too, the observatory still requires attention to the roof, as we now have the possibility of rain water getting in, this is a little disconcerting as the problem can only get worse and spoil the interior decor, so if anyone is prepared sometime during next summer to help out in a spot of roof felt laying please let me know. 
The Southam observing week arranged by Mrs Angela Turner got off to a very uncertain start by only receiving three adults two children and one nervous dog on the first night, however on the second clear night Saturday trade picked up, as we were kept busy from 7 till 10.00pm with people queuing up behind various telescopes for a look at different objects on show. Out of seven nights planned only three were observable so I think we were quite lucky with the weather. 
Due to the interest and expected fine weather Angela decided to extend the observing week to include the total eclipse of the Moon on Friday 17th Oct., this proved a great success with the public - needless to say though I missed the eclipse, but from all accounts from my non astronomical friends it seemed a dark eclipse. 
The observing week raised the sum of £26.70 for handicapped children and £11.35 for the society and hopefully a few more members as well. 
To all who took an active part in helping Angela, well done it really was appreciated. At the moment Angela is tentatively thinking of arranging another observing week next year, if so be sure to come along they really are a lot of fun and you'll learn something new in the process. 
The usual few who have submitted articles and observations during 1986 for MIRA I must once again thank you all, along with your kind co-operation of assisting me with type setting when I've requested it - this has been very much appreciated. 
Astronomical tip for next year, take a regular look at the Sun as I feel the minimum cycle is cycle is coming to it's close and spot activity will become more frequent, during the past couple of months the Sun has occasionally exhibited some fine specimens, so perhaps It may continue to do so on a more regular basis. 

See you all next year.


By Angela Turner


Craters Under High Illumination

When illuminated by a high Sun a crater is devoid of all shadows, thus it looks utterly different to when it was on the terminator.  Now what one see's is the crater in its raw state, with its relative surface albedo brightness variations, or its true reflecting-power.
In part one of "Drawing The Moon" I gave advice on how to tackle drawing formations under low illumination, where relief features are abundant and detail obvious. Drawing the Moon under high illumination however, is a completely different 'kettle of fish' altogether; here there are no shadows and thus no relief, formations literally appear white-washed.  This general whitewash effect when the Sun is high over a crater means that it is most difficult to draw exactly as the eye see's it, walls and features that were prominent when on the terminator can now totally disappear under this type of illumination. So it is practical to have a drawing that can be understood.  By exchanging artistic merit for numerical value this can be achieved in conjunction with a simple line drawing.
As no drawing ability is needed, just the ability to plot and record as accurately as possible all visible detail, which comes in the form of brightness variations, - the following method is by far the easiest and clearest way of drawing the Moon under high illumination.  I might add that its also quicker than a proper "as the eye see's it" drawing.

I've adopted the scale used by the great observer Schroter:
0  black
1  greyish black          6  light whitish grey
2  dark grey               7  greyish white
3  medium grey          8  pure white
4  yellow grey             9  glittering white
5  pure light grey       10  dazzling white
Home of these tones may be a little hard to visualise, but one soon gets
used to them with practice,
Again, as in part one of "Drawing The Moon" you will first need a outline of your chosen crater.  This can be made either at the telescope or from the map indoors, before the observing session commences, diagram "A".
Now sketch the boundaries using long dashed lines for the walls, diagram "B", and small dash's for all floor detail.
Using the Schroter scale give the detail a numerical value.
It helps to start with the bright albedo first, as this is most prominent under high illumination, diagram "C".
Then add the dark albedo, diagram "D".
Finally add all subtle albedo, diagram "E".

This technique can also be applied to any given crater under all illumination.  It may very well suit those people who would like to contribute towards lunar observation, but, who feel that they are not artistically inclined to make a proper drawing.  N.B. When using this technique under LOW illumination, REVERSE the use of numerical value, that is, start with the dark albedo first as this is most prominent under low illumination.

Below is an extract from one of Angela's completed observational notes   Ed. V.C.

Intensity Estimate on the crater PLATO   52N 10W

Observer. . . . Angela Turner
Location. . . . Southam, Warwickshire
Date . . . . . . 29th August 1985
Time . . . . . . 21h 48m - 22h 12m
Moon. . . . . . 13 Days
Conditions. . . Steady, thin wispy cloud, slightly foggy, very slight atoms turb
Instrument. . . 102mm OG

Part 3 by Rob Moseley 

I'm sure that, like me, many other readers of MIRA have been interested by the Rev. Tim Gouldstone's articles on the visibility of far southern stars from mainland Britain (see MIRA Dec 1983 and May 1986).

From the murky skies of Coventry my best effort so far, using 10x50 binoculars, is a positive sighting of the rather insignificant 5th mag. star SAO 197938 in Canis Major lying at Dec. —32° 12', though on the same night (December 23 1985) I also glimpsed κ Canis Majoris at -32° 30', this observation being hampered by rising horizon haze.
However, at the end of May this year I spent a few days in sedate Budleigh Salterton which at a latitude of N50° 37' 30" gave me almost a 2° advantage over Coventry. Using the same binoculars and armed with a copy of Norton's Star Atlas I settled down on the beach as for from lights as I could manage without getting my feet wet at 22.00 UT on the evening of May 29.
The sky was a fine one, with Venus radiant in the West, the muted dawn glow of the summer Sun behind me to the North and the ribbon of the Milky Way rising in the East. Over the sea horizon before me Saturn shone in the Claws of the Scorpion and red Antares followed close behind. My first sweep along that horizon confirmed my fears that some haziness lurked near it, but it only seemed to extend to an altitude of 2° or so. The horizon lay at Dec. —39° 23' and the 14 Hour line was on the Meridian.
I spent 15 minutes allowing my eyes adapt to the darkness. Already I could see the star τ Librae shining at mag. 3.6 less than 10° above the horizon. Using the binoculars again I examined the region around Antares. The limpid sky immediately revealed an obvious misty patch close by — M4, a splendid globular cluster rivalling M13 in Hercules but always a difficult and disappointing object for northern observers. I returned to the task of finding my southern stars. Among others the following were identified:

χ Lupi (mag 4) -33° 37'

ε Scorpii (mag 2) -34° 17'

θ Centauri (mag 2) —36° 22'

θ Centauri was on the Meridian, at an altitude of only 3°, and several other fainter stars of Centaurus were seen to the North of it. I was delighted by my first ever view of the northern stragglers of this magnificent constellation. In retrospect I am also surprised at the easy visibility of ε Scorpii, - which at the time of observation was almost 3 hours East of the Meridian. It must then have been well under 2° above the horizon.

This is a fascinating exercise, taking the observer into areas of the sky rarely visited. If you are going on holiday to the South coast of England in the future be sure to take your binoculars. . . and a Norton's Star Atlas.

Theta Orionis - "The Trapezium" 
By Rob Moseley 

I found Richard Barrett's observation (see MIRA 13, May 1986) of this famous multiple system of great interest, due particularly to the apparent magnitude anomalies he records.

The following drawing is a precise representation of the group based on data contained in Sky Catalogue 2000 (Vol.II)

The magnitudes of the components are listed as:

 A - 6.7 B - 7.9 C - 5.1 D - 6.7 E - 11.1 F - 11.5

(There are two Further stars involved, G & H, but these are excessively faint at mags. 15 & 16) 

Let me first say that Barrett did well to pick up star F at all using only a 4 inch reflector in urban conditions. But why was not star E seen? There is a genuine mystery here, as I know Barrett's eye to be far too sharp to miss it in normal circumstances. E is much more prominent than F for two reasons; firstly it is nearly half a magnitude brighter, and secondly F is prone to be swamped by the light of nearby C, the brightest member of the group. Its worth noting that star E was fairly easily seen by several Society members (with little observational experience) using the 6½" inch refractor at the College Observatory on the evening of February 27th this year. All four "Trapezium" stars were easy objects - but there was no trace of F.
As well as the unusual prominence of F, Barrett also records star B as "elusive". According to the reference books this star is an Algol type eclipsing binary with a period of around 6 days and an amplitude of just over half a magnitude. Yet even at its faintest this star should be three magnitudes brighter than F.
Star F was discovered by Sir John Herschel in 1830 using an 11¾" inch refractory yet SW Burnham saw it with only 3 inch aperture on several occasions. Both E and F have been thought variable in the past. Otto Strove once remarked that "the existence of so many variable stars on such a small space in the central part of the most curious nebula in the heavens must of course induce us to suppose these phenomena intimately connected with the mysterious nature of that body." In fact, modern studies of M42 have revealed several hundred variable stars in the central regions.
Star B (BU Orionis) and also star A (V1016 Orionis) we known to be variable. To my mind Barrett's observation re—opens the question of variability in other members of the "Trapezium" group. A careful and regular monitoring of the "Trapezium" may prove a worthwhile observational project for any Society members owning telescopes of 3 inch aperture or larger.

Detail of Solar activity after approximately one solar rotation

By Vaughan Cooper


INSTRUMENT    6" Reflector  x60
ROTATION No   1774
DATE               26th April 1986
UT                   10h 00m
CONDlTlONS    Definition a little poor

P  =  -24.96
Bo =  -4.7
Lo =  199.0

INSTRUMENT    6" Reflector  x60
DATE              26th May 1986
UT                 12h 15m
CONDlTlONS   Fair definition good at times

P  =  -17.7
Bo =  -1.3
Lo =  61.1


M41 NGC 2287

Date 21. 2. 86
Time 22 10 UT
Inst. 8.5 Reflector x80 (20mm H. eyepiece)

A nice open cluster with bright star members sprinkled around the field of view
Intermingled are the fainter stars
The 6th mag star 12 Canis Major is just out of the field of view. The brighter stars are 8th mag.
Sky very clear but interfering moon just over half full
Limiting naked eye mag 4.5
Eyepiece and finder dewing very quickly



Date 7. 8. 86
Time 23.00 UT
Inst. 8.5 Reflector x80 (20mm H. eyepiece)

One thick bar visible slightly brighter in lower middle.
No hint of 2 shape at any power, as seen on previous observations.

Observer B Merrikin



Date 20th March 1986
Time 21.30 to 22.30 UT
Colong. 30.55 to 31.05 morning
Conditions Ant. II
Inst. 6in. Reflector x120
Observer Vaughan Cooper

Clouds interrupted completion of observation


26W 29S

Flooded crater, with walls rising in places to 5,000 feet, there is only a trace of a central hill, the floor contains some detail, including a delicate rill.

28W 28S 

A well formed 3O mile crater, it is the twin of Mercator, there is a central hill.
Fairly good seeing made these craters most conspicuous.
Although Mercator does have some subtle floor detail, absolutely none was visible, the floor looked bland, and devoid of any detail.
The walls are not particularly pronounced anywhere in Mercator. Two craterlets can be seen in the ramparts - one on the eastern rampart, the other on the western rampart. A small crater-pit can also be seen, at the foot of the south wall. Some terracing to the S/W wall appeared slightly landslided. A minute amount of floor detail can be seen at the foot of the north wall, this is a bright patch with a small shadow and either, a hill, or a crater-pit next to it.
Campanus most outstanding feature was the excessive terracing in the M/W to S/W walls, being long and winding, it looks to have slipped towards the south wall.
The central hills looked fairly lofty, to the N/W of the central hills, on the floor is a conspicuous crater-pit, there is a area to the east of this crater-pit that is bright to the rest of the floor; the floor was dark, darker in fact than Mercator, which is supposed to have the darker floor. The area adjacent all round Campanus is ringed with bulges!

DATE. . . . . . . . 29th May 1985
TlME . . . . . . . . 21h 55m - 22h 25m
MOON. . . . . . . 10 Days
CONDITIONS. . Breeze, clear, very slight quivering of image
INSTRUMENT. . 102mm OG. x186
LOCATION . . . Southam. Warwickshire
OBSERVER . . . Angela Turner.



Date         20th March 1986
Time        19.00 to 19.45 UT
Colong.     29.3 morning
Conditions Ant. III
Inst.         6in. Reflector x120
Observer   Vaughan Cooper
Clouds interrupted completion of observation


Date . . 1986 June 16
Time . . 22.15 - 22.55 UT
Colong . 25°3
Inst . .  8½" spec. x230
Seeing . IV


Date . . 1986 June 17
Time . . 21.30 - 21.45 UT
Colong . 37°0
Inst . . . 8½" spec. x230
Seeing . III