BAA Lunar Section
Dedicated to amateur research and observation of the Moon
Topographical
Sub-section
By
Peter Grego
Drawing the Moon
Here are a few good reasons why visual lunar observing is as valid now as it ever was, and will remain valid in the future:
1. Drawing features has the potential to be a thoroughly enjoyable and extremely rewarding pursuit. If you don't think that you enjoy drawing, or were put off drawing by your art teacher at school, give it a try and stick at it for a while.
2. Drawings deliver a unique and personal record of observations.
3. Attending to lunar detail by taking the time and effort to draw it allows you to perceive a feature's finer points.
4. Making drawings enhances every aspect of your observing skills. Making notes, technical aspects of recording features (UT, etc) are learned in the process.
5. There is a real chance of scientific discovery.
6. You get to learn the lunar topography — those odd names get to stick in the mind. The Moon becomes a known place — when you look up at the Moon, it's like viewing a familiar city. Before long, the apparent confusion becomes familiar. Imaging doesn't offer such a learning experience.
7. You get to learn the changing appearance of features under varying conditions of illumination and libration.
8. The Moon is beautiful to look at. It's majestic, awesome, utterly fascinating.
9. You are free to pursue your own programs of observation — TLP, intensity estimates, sequential drawings of the same feature — or participate in the programs of astronomical societies.
10. There's a small but thriving community of visual lunar observers and recorders who love to talk about the Moon and compare notes.
In my view, it's a mistake to call imagers 'observers'. While much CCD work is good and really valuable, in my opinion it serves as an inspiration to visual observers rather than something that negates it. When you see a detailed CCD image, try not to think "well, I may as well put down my pencil for good because I can never hope to record anything like as much detail." Instead, compare the image with your own observations, or if you haven't observed that particular feature, investigate how much of the detail depicted can be seen visually, and how it might change through the lunation with the play of shadow.
Drawing techniques
It
is important to have confidence in your own drawing abilities.
Drawing should be an enjoyable pursuit, but it is surprising how many
people's experience at school art class tends to have been a negative
one - if this is the case, you have my permission to disregard
everything your art teacher ever told you! The lunar observer isn't
some kind of weird nocturnal art student - nobody is allocating marks
for artistic flair or the aesthetic appeal of an observational
drawing. What is important is the effort that an observer puts in to
the attempt, and observational honesty and accuracy count above all.
The aim of the exercise is to learn the topography of the Moon, to
attend to the fine detail visible through the eyepiece and record it
to the best of your abilities - not to produce an artistic
masterpiece. The finished results will be the products of your
efforts and a permanent record of your forays around the lunar
surface. Don't throw them away - keep all your lunar observations in
a folder, and you may be pleasantly surprised at how you improve over time.
At
the eyepiece, find your bearings with a reasonably detailed map of
the Moon that is easy to handle at the telescope - a photocopied set
of the lunar maps contained in this book may work very well. Select
and identify your target, such as an individual crater, and one
preferably close to the lunar terminator where most relief detail is
visible (drawing features that are completely devoid of shadow is a
specialist skill in itself). If the feature that you have chosen to
observe isn't marked on your map, make a note of any prominent
features nearby which will aid you in identifying the feature later
on. If it is possible, return indoors and make a basic light pencil
outline drawing of the features within your chosen area, using your
map as a guide. Take care to get the proportions and arrangement of
features right — this will save time and give you a distinct
advantage at the eyepiece. Remember that features near the Moon's
limb are affected by libration, and an outline copied from a map may
not be the same as how a feature is presented on the evening that you
have chosen to observe.
To
make regular pencil sketches, a set of soft-leaded pencils, from HB
to 5B, and an A5 pad of smooth cartridge paper are recommended. Basic
outlines of lunar features are first drawn very lightly, using a soft
pencil, giving you the chance to erase anything if the need arises.
Scale is important — thumbnail sketches will not convey nearly
enough detail, but an individual drawing that takes up the whole page
will take far too long to complete to one's satisfaction. I have
found that a drawing of around 100 mm in diameter is quite sufficient
for most observations. When shading dark areas it is best to apply
minimal pressure on the paper. The darkest areas of shadow are
ideally applied in layers of soft pencil rather than a frenzy of
heavy pencil pressure.
It's
reasonable to set yourself about an hour or two per observational
drawing. Patience is essential, because a rushed sketch is bound to
be inaccurate. Even if the clouds are threatening to obscure the Moon
from view, or if your fingers are feeling numb with cold, it's best
to have an accurate half completed drawing rather than an inaccurate
drawing of the entire area you have observed. Short written notes can
be made at the telescope eyepiece, pointing out any unusual or
interesting features that you have observed but may not necessarily
be obvious on your drawing. Of course, it is essential to note the
name of the feature you have observed, the date, start and finish
times (in Universal Time) of the observation, the instrument and
magnification used, and the seeing conditions. Copies of your
observational drawings ought to be made as soon as possible after the
observing session, while the information remains fresh in your mind.
Sketching
skills can be improved by drawing small sections of detailed lunar
photographs that appear in books and magazines. After several
attempts at 'armchair' Moon drawing you may surprise yourself at how
quickly you improve. The most important thing is to be patient and
not to rush, even if you are only practicing.
Cybersketching
— electronically-aided drawings
Digital
image meets observational drawing
There
is a reasonably simple modern solution to the problem of visual
observational accuracy in making a lunar drawing at the eyepiece, a
logical extension of Krieger's technique. Take a digital image of the
Moon, print it out and use it as an observing blank. The digital
image can be centred on the feature that you intend to draw, or you
can take a series of images of the terminator, from which you can
then choose an area to draw at the eyepiece. The image may be secured
with nothing grander than an ordinary digicam using the afocal method
(this is when the camera is squared up to the eyepiece). The image
needs to be good enough to show all the main detail of the area that
you intend to draw, but it need not be such a perfect image that
you'd submit it to Selenology for publication! This image is then
adjusted on the computer indoors. Crop the image to size, and adjust
its brightness and contrast so that it appears faint but distinct
enough to be seen using a red light at the eyepiece. If your image
shows any overt artifacts of processing, such as moiré
patterns, it is best to remove these before printing it out. The
print ought to be made in greyscale on smooth white paper, of drawing
grade (120 gsm or thicker), and the area that you're going to draw
needs to be at least 75 mm square. I use a laser printer, because
damp conditions may make an inkjet print unsatisfactory to draw upon
at the eyepiece. The template can be ready for use at the eyepiece
within a few minutes of the image being taken. At the eyepiece, I
prefer to clearly delineate all the main areas of shadow first, as I
do when I make an unassisted drawing of the Moon, before
concentrating on the detail. I usually work my way around a drawing
from the top left, downwards, to prevent smudging, since I'm right-handed.
My first attempts were made using nothing more exotic than a 250,000 pixel Casio QV-11 compact digital camera capable of storing dozens of images. This required linking to the PC via cable, so the camera had to be unhooked from the telescope and brought indoors. I now use a Ricoh RDC-5000 digicam (1.3 megapixel) or a Trust 820 PowerCam (4 megapixel), both of which have a removable storage card that can be inserted into the PC. They both deliver reasonably good images of the Moon, the Ricoh having the advantage of an optical zoom, while the Trust requires the use of a high magnification eyepiece to deliver a close-up view.
The immediate advantage of the technique is the ability to draw relatively large and complex areas of the lunar surface with surprising speed and accuracy. Confident, and armed with the knowledge that the positioning of the main features has been attended to, the observer is free to concentrate on areas of detail that might otherwise have been neglected due to time considerations. The technique will not make you a better observer, but it will make your observations more accurate, and accuracy is the foundation upon which all scientific observations rest. It is also a tremendously enjoyable pursuit, and something worth experimenting with, even if you haven't given the Moon much thought in the past.
Once
the observational drawing is made, that need not be the end of the
process. Indoors, the drawing may be retouched, the areas of dark
shadows blackened, details sharpened and areas of roughness smoothed
over. Alternatively, the drawing may be copied manually and converted
into a neat drawing, or scanned and a print of it used as a template
for a neat drawing. I prefer to process the scanned observational
drawing using computer software (I use Corel PhotoPaint and
PaintShopPro) to enhance its appearance by using (mainly) the median
filter and tone adjustment. The drawing may also be cut out and
placed upon the original digital image, and once its edges are
blended in with the background the effect can be rather pleasing.
Sketching
on PDAs, UMPCs
and tablet PCs
Lunar
cybersketches made on PDA may well take up the entire screen area,
or a substantial portion of the central area of the screen, which,
since it measures just a few tens of square centimetres in total, is
perhaps slightlye smaller than one might choose to make an actual
observational sketch with pencil and paper. However, the zoom tool
can be used to magnify and work upon any areas wherever it's
necessary to add detail too fine to accurately portray in the regular
display mode. It goes without saying that it's important to ensure
that the touch screen on mobile devices ought to be calibrated as
accurately as possible, otherwise you may find yourself using the
zoom tool a little more than really necessary in order to rectify mistakes.
Because
UMPCs and tablet PCs have more generously sized screens than PDAs,
it may be tempting when using these devices to do most of the work on
a field sketch which is zoomed in so that its edges to fill the
entire screen. From experience, however, I've discovered that a much
more comfortable and efficient size for laying out a cybersketch is
within the area defined by the 90 degree arc which can be drawn by
one single stroke of the stylus without moving the arm, the end
points of the arc determining the diagonal proportions of the sketch.
For me, this is about 11 cm on the diagonal, or around 7 x 9 cm
(landscape), which means that it fits nicely on an A6 size page (10.5
x 14.8 cm / 4.1 x 5.8 inch) set to 300 dpi with a little room to
spare around the margins. Finer detail on the cybersketch can of
course be added by zooming in to specific areas.
Line
drawing
An
alternative to making shaded pencil drawings at the eyepiece is to
represent features in outline form. Many observers choose to make
annotated line drawings at the eyepiece, using the technique as a
form of observational 'shorthand', along with intensity estimations
(see below). The line drawings, and the written information that
accompanies them, are then converted into full tonal renditions in
pencil or ink, after the observing session. However, line drawing
should not be considered a quick and easy alternative to tonal
drawing, since a line drawing ought to be drawn just as carefully
with the same amount of attention to detail.
Obvious
features such as the rims of prominent craters and the sharp
outlines of shadows cast by mountains are represented by bold lines.
Try to avoid depicting of lunar mountains as upturned 'V' shapes
— this might be fine for cartoon strips, but it only serves to
confuse the appearance of a lunar observational drawing. If a part of
the drawing depicts mountainous terrain, attempt to delineate the
borders of the terrain, outlining the main peaks, features of relief
and the main shadows. Similarly, a detailed area of fairly homogenous
rough terrain that contains perhaps too much fine detail to depict
accurately ought not be drawn as a mass of dots and jagged squiggles
— simply try to mark the borders of the terrain and label it
'rough terrain'. Subtler features like lunar domes and wrinkle ridges
may be recorded with lightly applied lines. Dashed lines can be used
to delineate features like rays, and dotted lines can be used to mark
the boundaries of areas of different tone.
Line
drawings do require plenty of descriptive notes to accompany them
— far more than a well-executed tonal pencil drawing, which can
stand on its own with the minimum of notes. The line drawing method
has the advantage of requiring the minimum of drawing ability —
although observational accuracy is just as important as in tonal
drawing. When done properly the method can be as accurate and as full
of information as any toned pencil drawing. Performed by someone used
to the technique, line drawing can be quicker to accomplish than a
tonal pencil sketch.
Intensity
estimates
A
basic annotated line drawing can convey the appearance of a lunar
feature and its topography in great detail. However, along the
terminator the Moon's surface varies in brightness from pitch black,
through all shades of grey, to dazzling white. It would be quite a
laborious task, if not impossible in many cases, to go to the trouble
of labelling each area of different tone on a line drawing in
longhand. To make the task manageable, an intensity estimates
shorthand is used to accompany line drawings. This requires the
observer to estimate of the brightness of each distinct area depicted
on the drawing, using a scale of 0 to 10 - 0 for the blackest lunar
shadows, to 10 for the most brilliant areas.
Intensity
estimates scale
The
tonal examples given below are based on a general binocular or low
power telescopic view of areas that are illuminated by a midday Sun.
Each area breaks down into further tonal grades when scrutinised at
higher magnification, and each area will tend to appear darker the
nearer it lies to the terminator.
0 — Black: the darkest lunar shadows.
1 — Very dark greyish black: dark features under extremely shallow illumination.
2 — Dark grey: the southern half of Grimaldi's floor.
3 — Medium grey: the northern half of Grimaldi's floor.
4 — Medium light grey: general tone of area west of Proclus.
5 — Pure light grey: general tone of Archimedes' floor.
6 — Light whitish grey: the ray system of Copernicus.
7 — Greyish white: the ray system of Kepler.
8 — Pure white: the southern floor of Copernicus.
9 — Glittering white: Tycho's rim.
10 — Brilliant white: the bright central peak of Aristarchus.
The
eye is capable of differentiating between hundreds of shades of
grey, so a skilled observer can easily subdivide the basic scale yet
further. Unlike variable star estimations, these tend to be
qualitative visual estimates, rather than quantitative ones. For
example, an individual mountain peak approaching the evening
terminator may not appear particularly brilliant, having an intensity
rating of perhaps 6 or 7. But once the dark shadows of lunar night
spread around the landscape surrounding it, the mountain peak may
appear like a dazzling beacon, with an intensity rating of 9 or 10,
glinting beyond the terminator — even though the peak is in fact
less bright than when the mountain lay in full sunlight.
Copying
up
Nobody
has the ability to produce completely error-free observational
drawings at the eyepiece, so it is best to prepare a neat copy of
your observational drawing as soon after the observing session as it
is practically possible, while the scene remains vivid in your mind.
A fresh drawing prepared indoors will, it is hoped, be far more
accurate than the original telescopic sketch that it is based upon,
as the observer will be able to recall little things about the
original sketch that perhaps weren't quite right and needed to be
rectified on the neat drawing. To improve the accuracy of a drawing
it can be useful to base the general outlines of a neat drawing upon
an outline blank, a map or photograph of the area that has been
observed - this perfectly legitimate, as long as the observer isn't
adding any detail that wasn't actually observed. The neat copy of
your original telescopic sketch can be used as the template for
further drawings, or used to electronically scan or photocopy.
Copied
drawings may be prepared in a variety of media. Superb results can
be achieved using India ink washes, and paintings in gouache — a
watercolour medium that it is possible to apply fairly thickly and in
a controlled manner — are excellent for reproducing observation
on a larger scale for exhibition purposes. Both these techniques
require proficiency in brushwork, and although a description of the
methods involved is beyond this book, practice, experimentation and
perseverance will pay big dividends.
My
own preference whenever I make a pencil sketch — soft pencil on
smooth cartridge paper — is by far the quickest and least fussy
medium. Once completed, pencil drawings need to be sprayed with a
fixative so that they don't smudge if they are inadvertently rubbed.
Regular copy shop photocopies of tonal pencil drawings are not quite
good enough to submit to astronomical society observing sections or
for publication in magazines, as the full range of tones in the
drawing will not be captured, and it may appear somewhat dark and
grainy. These days, however, most observing sections are happy to
accept a high quality laser print or a digitally scanned drawing.
Some commercial magazines may insist on having the original artwork
to work from, or at the very least for high quality, high resolution
scans to be submitted on floppy disc or by email.
Ink
stippling
Ink
stippling is one method of reproducing observational drawings that
looks absolutely superb when it is done skilfully. Closely spaced
dots of black ink are used to convey the illusion of shade — the
darkness of the shade increases with the more closely spaced and/or
bigger the dots are. Areas of black shadow are simply blacked in with
ink and a brush. Being composed of thousands of individually applied
black dots, stippled drawings reproduce very nicely even when they
are photocopied. Stippling must be performed using a set of technical
pens with a range of nib sizes — an ordinary fountain pen, felt
tip or ballpoint pen simply isn't good enough. Stippling takes a
great deal of time, and requires patience and an exceedingly steady
hand. An individual capable of producing wonderful pencil drawings
may not necessarily be able to master stippling. For example, my own
efforts to get to grips with the technique have not been too
successful. Stippling is an exacting process that does not easily
forgive lapses of attention, and drawings do not welcome extensive
alteration. A small group of dots inadvertently placed too closely
together may indicate a non existent feature. Stippling in too
regimented a fashion — by stippling along straight lines, for
example — may give rise to unwelcome artefacts. So, as well as
having a disciplined eye and hand, there must be a certain looseness
of technique and an ability to keep the bigger picture in mind. In
the world of lunar observation, there are only a handful of truly
competent masters of the stippling technique.
Care
for your archives
Tempting
though it may be to discard old drawings, they represent a permanent
record of your observations and hard work at the eyepiece. At the
very least, comparing old observations with more recent ones will
demonstrate how much your skills of observation and recording have
improved. Older observations can be compared with more recent
observations of the same feature. Remember that constant changes in
illumination and libration means that lunar features can appear
markedly different from one hour to the next, as well as from one
lunation to the next, and your drawings may have captured an aspect
of a feature that is rarely observed. Original drawings can be used
as the basis for subsequent copies for the observing sections of any
astronomical societies to which you belong, or for publication. For
these reasons, do hang on to your original drawings for future
reference. Devote a folder or a ring binder to your original lunar
drawings and store them safely in a dry environment.