MIRA 13
May 1986



Drawing The Moon

By Angela Turner

PART ONE  Craters Under Low Illumination

Drawing the moon is not as difficult as it might first appear, and certainly improves with practice.  While it might be a laborious procedure, especially when compared with the time it takes to make a photographic exposure of the lunar landscape.  There is without doubt far more reward and pleasure to be gained from undertaking lunar drawings.  Let me give you a for instance; the human eye can discern far more detail than a camera can ever record, thus your finished drawing will contain far more detail than the photograph, especially where that detail is most subtle, such as in the walls and on the floor of the crater.
Firstly — you will need a set of soft pencils, B's are perfect.  I work with B, 2B, 3B and 4B pencils.  B being the lighter toned, and suitable for subtle details, while 4B is the darkest and suitable for all black lunar shadows.  The 2B and 3B are used for all moderate tones, such as prominent terracing in walls and floor coloration.  Being soft pencils they are easy to rub out should you make a mistake.  There is nothing worse than to use a hard pencil, make a mistake and then find that it will not rub out and you are then left with very ugly groves across your drawing!  Also select a good quality drawing paper, this will enhance your drawing immensely and serve to make your drawing easier to shade.
Having now prepared yourself with the appropriate equipment, its time to take yourself out on the next available clear night that DOES contain a Moon!  Its preferable to catch the Moon in a good phase, that is three days before, or after, first and last quarter.  I say this because, it will only serve to put people off drawing the Moon, should you attempt drawing limb features first.  Limb features are fairly difficult, and experience is preferable before attempting to draw them.  The central portion is by far the best region for the novice to make a start, here formations are well presented with easily discernible detail.  Follow the terminator (the line that divides the day from the night) over, and scan down the terminator for interesting subjects.  These do not necessarily have to be the large craters that are so abundant, many of the smaller craters are just as interesting and fascinating as their "big brothers".
After selecting your chosen subject you are now ready to make a start.
At first sight you may well think it downright impossible to draw what you are looking at, after all, look at all that detail, and you may well ask "just WHERE DO I start?".  Well you start by breaking the detail up and adding it into the drawing a bit at-a time as you progress through it.
Look at diagram "A", this is just the outline of the chosen crater - draw the outline first, very lightly so that only the specific shape of the crater is on your paper. From this your drawing will take shape.
Now take the 4B pencil, and shade in all the black shadows; don't be afraid to apply the pencil thickly in order to obtain a good interpretation of the blackness of these shadows, see diagram "B".
Next draw in lightly with the B pencil the outlines only of all the bright areas,
see diagram "C".
You can now shade in the darker tones, those that represent the upper grey tones using the 2B and 3B pencils, see diagram "D".
Your drawing should now be recognisable as a Moon crater consisting of three added tones, BLACK, GREY and WHITE.  Now you can concentrate upon the detail, if seeing is good there will be a fair quantity of this, so please take your time when adding detail in. The detail will be subtle and consist of terracing in walls and floor detail.  Keep checking that the detail is being added in, in the correct position.
When you are quite sure and confident that you have added all the visible detail, you should be the proud owner of an artistic lunar drawing something along the lines of diagram "E"!!!  Its worthwhile too, to make a copy of your drawing as soon as possible, as the one made at the telescope is usually pretty scruffy!!
Remember though, that you have a lot of things working against you, inadequate lighting, coldness, wind, clouds, atmospheric turbulence, tiredness, dewing etc, etc, etc.  So please don't be too disappointed if your first attempts at drawing the Moon don't altogether turn out artistically.  I was very disappointed with my first attempts - press on, its practice and enthusiasm that counts.
In part two of "Drawing The Moon" I will be giving advice on how to draw the lunar surface under a high Sun (a lunar high Sun that is).
Meanwhile I wish you every success on drawing the Moon under a low Sun!









Astronomical "Seeing" 

By Rob Moseley

In most areas of telescopic work observers will always record the "seeing" encountered.  This is a tern that sometimes confuses the beginner — so what exactly is meant?
Basically, "seeing" refers to the steadiness of the atmosphere.  It is important to differentiate between seeing and transparency - the two factors should be recorded separately.  It is of little use to state that "conditions" were good or poor without further qualification.
Seeing is usually recorded on the widely accepted Antoniadi scale (Antoniadi was an eminent Greek-born planetary observer, for many years the Director of the BAA Mars Section.) This is a simple scale but it is adequate for most purposes. It runs thus:

I   — Perfect seeing, without a quiver.
II  — Slight undulations, with moments of calm lasting several seconds.
III — Moderate seeing, with larger tremors.
IV — Poor seeing, with constant troublesome undulations.
V  — Very bad seeing.

Many factors can influence the atmosphere and produce turbulence.  "High" seeing refers to effects originating at high altitudes caused by large scale pressure changes associated with meteorological fronts.  It is an old piece of observing lore that an East or North East wind direction tends to produce particularly poor seeing - though the precise reasons for this are uncertain. High seeing effects tend to produce a rapidly vibrating image, and the observer can do nothing about this cause of unsteadiness - just suffer it!
"Low" or "local" seeing is another matter.  Muirden has pointed out that observers on the lee side of a city (in most cases the East side) will suffer poor seeing, while the observer actually in the city will enjoy relatively favourable seeing since he is in the centre of a "warn spot" and the air above him will be relatively homogeneous.  Hilly surroundings will also produce turbulence, especially if a wind is blowing.  Even more localised are the effects produced very close to or (in the case of a reflector) actually inside the telescope.  Equalisation of temperature is the all important factor here.
If a reflector is taken out into the garden on a cold night it will retain a column of warm air above the mirror for some time and observations must be delayed until this has dispersed.  My own telescope regularly displays the effect of these "tube currents" for the first 20 minutes or so of an observing session.  Open or skeleton tubed reflectors are not so prone to these effects, and the free circulation of air enables the optics to cool off quickly too.
Refractors are little affected due to their closed tubes - but they too must be left to equalise for a short period.  It almost goes without saying that proximity to a source of heat should be strictly avoided.  An object situated over the roof of a house in winter is bound to be affected by thermals (although the modern trend of loft insulation has produced astronomical benefits!) - and trying to observe by poking a telescope out of the window of a heated room is a familiar horror story...
How do you make a judgement on seeing?  Is it II or is it III?  This is largely a matter of experience, but the most critical test is to look at a reasonably bright star (Polaris is the most convenient).  Centre it in the field of view using a moderate magnification and rack the image slightly out of focus.  From a point the image will expand into a small disc.  If the edge of the disc is clear cut and steady the seeing is good — if it wobbles and distorts into strange blobs and splodges then you're in trouble!  In perfect seeing an in focus star image should be a minute disc (in the case of a refractor surrounded by motionless concentric diffraction rings).  In practice this will usually be seen as a small disc with a tiny bright "nucleus"
Reflectors also have a tendency to produce diffraction spikes, caused by the arms supporting the secondary horror.  The worse the seeing the larger and more shapeless the star discs become, so don't expect to see then put on a text-book performance very often.  Antoniadi I seeing is a rare event.  Over the past two years I have recorded it only once, and then for a very short period.
The tine of night can also affect the quality of seeing.  Some observers maintain that an hour or so of good seeing is often to be had soon after sunset.  However, this has never been my experience, and I think that the marked changes in air temperature at this time of day tends to make this claim a little difficult to account for.  (I await correction.)  There is also a widely held view that seeing improves as the night wears on, as the ground temperature slowly equalises with the layer of air above it.  This would appear reasonable, but I have suffered appalling seeing before dawn on numerous occasions.  In fact, my general experience has been that there are no hard and fast rules.  Not in this country at least!
Seeing will seldom remain at a constant level for very long.  If an observing session stretches over several hours the seeing may often vary between two or even three points on the Antoniadi scale.  Most taxing of all are the nights when the image will bubble and seethe for long periods and then suddenly steady for a few seconds.  The observer must be ready to utilise these brief "windows", and it usually leans a long cold wait and a lot of effort to maintain concentration.  (Needless to say, "Sod" dictates that when the moment cones the hapless observer is making some adjustment to his telescope, or having a fag...)
Seeing is especially important to the planetary or double star specialist.  Elusive detail on a planetary disc will be blotted out by unsteady air, and faint companion stars will be blurred from a point source of light into an extended, invisible blob.  Amorphous, extended objects like nebulae and comets are not so badly affected.  For these creatures a very transparent sky (which often produces poor seeing) is all important.
As a rule of thumb for the planetary observer look at a bright star at - a reasonable altitude before an observing session with the naked eye. If its light is reasonably steady then the seeing should be OK — if it is twinkling violently against a black sky then forget Jupiter and have a look at M33!





HOW LOW CAN YOU GO - PART 2
By Tim Gouldstone

Readers may remember the comments in the December 1983 issue of MIRA when I investigated the stars in far south dec. as observed from Ansley (lat 52° 31'
N.).  I managed to glimpse kappa Columbae at -35° 07' S. dec.
Having moved to St. Keverne (lat 50° 03' N.) the constellation of Columba is much more in evidence, not so much because of the decreased lat. as a result of much clearer skies and the absence of light pollution on the southern horizon.  7x50 binoculars show stars down to 7 mag as far south as -35°.
Steve Anderson (a local amateur astronomer) and myself decided to go down to Lizard point (lat 49° 57' N.) to see just what sort of low altitude clarity was available there.  We parked right on the point at the Lizard, S of the lighthouse on the concrete read leading to the old lifeboat house. Armed with a torch (to stop us falling off the end of England and to read the atlas) we were rewarded on 1986 Feb 5 with a sky of magnificent transparency.  M1 and M33 were easy objects in 7x50 and 12x40 binoculars, and the open clusters in Gemini and Auriga were a splendid sight.  Even M78 in Orion was seen.
Observing the horizon was more difficult - there is a very powerful lighthouse at the Lizard whose beams slice through the night and periodically illuminate the horizon.  So light pollution is not only a problem at Coventry.  However we were able to see Xi Columbae (mag 5.02, -37° 07' S. dec.) and Steve glimpsed the pair of stars shown in Norton's just S, of Xi at about -37° 30'.  At 21h 15m Pi Puppis (-37° 00') appeared in the sky west of south, visible in 7x50's as were the two stars cLose by, shown in Norton's as v1  and v2.
At this time Xi Puppis was still 1h from culmination so the conclusion is that on this night it should theoretically be possible to detect objects down as far as -38° S. dec.
At 21h 35m we adjourned to thaw out at the Lizard Hotel - lying on one's back on the concrete road at the Lizard scanning the zenith with binoculars is a very cold experience, but perhaps this account is the first recorded observation from Britain's most southerly point!
Steve and friends are trying to get a 'West Cornwall Astronomical Society' going.  There is quite a lot of interest but people are scattered in this rural area and it's not always easy to get folks together.







Eudoxus


A sharp rimed crater of 40 miles diameter, with walls attaining 11,000 feet.
The drawing is not completed due to sky clouding over and bad seeing.  A fuzzy Moon made definition poor.
No great amount of detail could be discerned due to bad seeing at the time of drawing.
Eudoxus was near the terminator and thus was just under half in shadow.
The central massif appeared fairly lofty, standing out well in the black shadow; the western part of the massif appeared detached to the eastern.  A darkish colouration to the floor is seen due N/W of the massif, the exact size of this is in doubt due to the bad seeing conditions.
The north wall is very rugged, with hills at the foot, there is a craterlet in the rampart.
Bad seeing again made it difficult to discern any subtle detail along the north, west and south-west walls; a few subtle terraces were made out in the S/W wall, although this wall appeared quite heavily landslided.  Some dark terracing is easily seen riding the N/W wall.
The bases of the north, west and south-west walls are unfinished.
A craterlet is seen in the eastern rampart.

DATE            24th June 1985
TIME             22h O5m - 22h 37m
MOON           6 Days
CONDITIONS  Slight wind, thin wispy cloud, atmos clarity bad, deteriorating
INSTRUMENT  102mm OG x186
LOCATION     Southam, Warwickshire
OBSERVER     Angela Turner



MAUROLYCUS


Date         5th October 1985
Time         5h to 6h 15m UT
Moon        20 days old
Conditions  good
Reflector   6in x120
Observer   Vaughan Cooper

My drawing shows the majority of the floor of this 68 mile diameter crater in shadow in the middle of which can be seen the central peak just catching the last rays of the setting Sun, with also the tops of a mountainous ridge running from the central peak towards the eastern wall seen within the shadow as a thin even line with only one break in it near the central peak.
The area in and around the northern wall shows various small craters and terraces breaking into the main crater.


SUN


BAA SOLAR SECTION

INSTRUMENT  6in Reflector
ROTATION No 1771
DATE             8 Feb 1986
UT                12h 00m
CONDITIONS  Definition not very good
OBSERVER      Vaughan Cooper

P  =  -14.82
Bo =  -6.47
Lo =   33.1

NOTES
Approximately 14 hours after my observation, reports of a bright Aurora Borealis was seen in England as far south as Essex.  The following night I specifically looked out for any further activity that might still be in progress without any success.




M42 The Orion Nebula


4" spec.   x133  1/4° field
Date          1985 February 11th
Time          20.00 - 22.OO UT
Seeing       II/III
Observer    Richard Barrett

Note nebulosity around star to lower left of centre.
An interesting feature of this observation is the fact that the star in the Trapezium designated B with mag. quoted as 8.0 to 8.7 (var.) was far more elusive than F, at mag. 11.