An Introduction to Planetary Sketching

I hadn't expected to see the feature on Jupiter that night. I had recently purchased a used Edmund 4-1/4" f/10 equatorial reflector (for $60, which was a lot for me at the time) and that night was going to be first light. During the day I cleaned the telescope, collimated the mirror and aligned the finder, and as it started to get dark I set the scope outside to let it cool down.

As Jupiter rose higher in the eastern sky I swung the telescope over to it. I was surprised how much brighter and larger it appeared then in my smaller 60mm refractors that I had used for a year up until then. As I scanned the planet with the low power eyepiece in I saw what appeared to be a large red colored object. I inserted the high power eyepiece and focused and realized that I was finally seeing the Great Red Spot live up to its namesake for the first time.

I took out my flashlight, sketchpad, color pencils, and began to make a drawing of the planet, noting the date and time, sky conditions, telescope used, and magnification. It was mid-September 1974, and this is the drawing that I made at the eyepiece that night:

Jupiter, September 15, 1974, 2:30 UT - 2:50 UT, clear sky with fair seeing. Callisto, Europa, and Io are to the left of the planet, while Ganymede is to the right. Edmund 4/1-4" f/10 reflector, 135x

Jupiter, January 2, 1977, 5:15 UT - 5:50 UT, clear sky with fair seeing. Europa is on the limb of Jupiter, while its shadow is visible in the Red Spot Hollow. The Great Red Spot (GRS) had faded to a dim gray color in 1976. Io and Ganymede are to the left of the planet. Criterion RV-6 reflector 6" f/8 reflector, 140x

Saturn, January 2, 1977, 4:00 UT - 4:50 UT, clear sky with fair seeing. Cassini Division prominent. Equatorial Zone appeared white in color. Equatorial Belt light brown in color. Tethys is to the left of the planet, Rhea is above, and Titan is to the right. Criterion RV-6 reflector 6" f/8 reflector, 140x

Why Draw?

Making a drawing while you are at the eyepiece observing the planets is one of the best ways to increase the detail that you see. Not just on the planets or moon, but also in Comets and Deep-Sky objects as well. This is because you are training your eye to see more detail.

When I first started observing the planets I did not know anything about training my eye to see more detail. I simply made drawings because I wanted to make a permanent record of what I saw. The first one I made was of Jupiter using a 60mm achromatic refractor. Before setting up the telescope I took a sketchpad and drew a round circle on it to represent the globe. Next, while at the eyepiece I noted the date and time of the observation, telescope and magnification used, and sky conditions.

The first time I observed Jupiter I expected it to look a lot like the photographs I had seen it in magazines and books taken with large professional telescopes. But what I saw wasn't much, just three brown-colored bands on a yellow ball. All three belts appeared to be the same width, one near the center of the globe, and the other two not far from the North and South Polar Regions. Even though what I saw was nothing like the pictures in the books I thought it was neat to be able to see detail on a planet almost 500 million miles away, so decided to observe again. Plus it was fun to see the four Galilean moons as they changed position night to night.

After a few weeks of observing and making drawings of Jupiter I gradually began to see more detail. The three belts no longer appeared to be the same width. The ones near the South and North Polar Regions appeared thinner then the one near the center. Also, the center belt now appeared to have white colored area in the middle. On other nights I saw a shadow transit from one of the moons cross the face of Jupiter, and even the Great Red Spot, even though I could not quite make out the red color.

Since I was using the same telescope as a few weeks ago, the same magnification, the seeing conditions were about the same, and yet was seeing more detail, I realized that something else had changed. My eye was getting trained to see finer detail. Instead of just noting where the belts were I began to look for other more subtle features.

Getting Started

It may seem like a lot of work to make a drawing at the eyepiece. You may be sitting there thinking it is just extra stuff you have to carry outside with you, and besides you don't feel you are much of an artist. The thing is you don't need to be an artist to make a drawing at the eyepiece. All you need to do is to record on paper what you see.

Venus April 13th, 2012, 23:20 - 23:40 UT, seeing fair - poor, transparency 5. TMB 175mm f/8 apo refractor on a homemade Dobsonian-style mount. Magnification 170x- 298x. Filters used: Baader deep blue (W38A) and yellow (W25). These filters helped to enhance the dusky appearance in clouds. The Baader deep blue (W38A) and yellow (W25) filters brought out the cusp extensions in the north and south polar regions. The cusps were not visible without the filters.

Lets start simply. The next time you go out to observe a planet, such as Jupiter, get a sketchpad or notebook and draw a circle on one of its pages, say two and a half inches in diameter. Note that Jupiter's disk is not a circle but an ellipse, as the planet bulges slightly at the equator due to its rapid rotation rate: it completes a rotation in less then 10 hours.

There are pre-drawn observing forms for the planets, including Mars, Jupiter, and Saturn available from both The Association of Lunar and Planetary Observers (ALPO) and The British Astronomical Society (BAA). Both are listed on my Links Page. Also a simplified Jupiter observing form was printed in the October 2000 issue of Sky and Telescope magazine on page 128.

If these pre-drawn observing forms don't seem to be the right size for you, for example you may feel more comfortable if the forms were a little smaller or larger to match better with the view you are getting through your telescope, you can just use a Xerox machine to reduce or enlarge them. Note too that the tilt of Saturn's rings changes from year to year, so you will need to use a different pre-drawn observing form during the course of an observing season.

Mars, July 25, 1986, 4:45 UT, with some of the features identified. Melt band visible along edge of South Polar Cap, as well as small rift. Solis Lacus prominent. Limb cloud noted in North Polar Region. Astro-Physics 6" f/9 refractor. Magnification 198x with Wratten 21 orange filter. Seeing 5-6 on ALPO scale.

Bring your form or sketch pad outside with you when you go out to observe. Here is a list of some basic supplies to help you get started:

1.) Get a clipboard to hold your observing form. This makes it easier to make the drawing while at the eyepiece. If you are using a sketchpad make sure it has a firm cardboard back to make it easier to draw.

2.) Attach a book light to the clipboard or sketchpad, or have some other small flashlight that you can hold in your hand along with the clipboard or sketchpad, so that you don't have to hold a flashlight in your mouth while you are trying to draw.

3.) Decide whether you want to make your drawings using either a lead pencil or color pencils. Have a soft eraser handy as well. If you want to use a lead pencil, you can start out with a #2 lead pencil. When you are making your sketch you will want to be able to show that one feature is darker or lighter then another, and you can either do that using the #2 lead pencil, or buy pencils that have different shades.

Art supply stores carry these pencils, such as those made by Sanford. Several to consider getting would include a 4B (darkest), 3B (medium), H (lighter), and 4H (lightest). These pencils tend to be easier to work with in terms of reproducing subtle planetary features than using a #2 pencil.

4.) If you want to use color pencils, art supply stores carry different brands. You can buy a box of colored pencils from Prismacolor, Berol, or from other manufacturers, or if the cost of an entire set seems like too much money just buy a few pencils to get started with.

Prismacolor is a good brand to get. Another item to get while at the art supply store are blending paper stumps, as these help to produce smooth color renditions. Once you have made a few drawings you may find that you want other specific colors, and most art supply stores carry individual pencils for sale, from companies like Prismacolor, Berol, Derwent, Rexel, and Sanford.

5.) Note that if you are making a color drawing try using a flashlight with a white light rather then a red one as it us difficult to distinguish colors when using a red light.

It is a good idea to keep your clipboard, forms, flash light or book light, and pencils together in one place so you can grab them on a moments notice. There are times when you don't feel like making a drawing because you have along day at work and are tired, or just want to get a quick observing session in.

Murphy's Law being what it is though it is nights like these when you don't have your drawing materials handy that the seeing can suddenly get very good or excellent, and you end up back inside searching for 20 minutes your pencils or forms. When you finally get back outside the seeing has gone from excellent to poor.

Once your telescope is cooled down pull your chair up to the eyepiece. Note that you will find it much easier to sit and make a drawing then try and stand. Record on your paper the date, the time you begin your observation, the telescope and magnification used, sky conditions (is it clear, hazy, partly cloudy; does the image of the planet seem steady). When you are recording sky conditions remember that you are considering two factors. One is transparency, and the other is seeing.

Mars, May 2, 1999, 2:25 - 3:15 UT, seeing 5 - 6 (0 worst, 10 best), transparency 2. Central Meridian 112.11 degrees. Astro-Physics 7.1" f/9 EDT refractor on homemade Dobsonian-style mount. Magnification 203x-289x with Baader binoviewer.

Transparency and Seeing

Transparency is equal to the faintest star visible to the unaided eye. Many observers use the stars in Ursa Minor, The Little Dipper, to determine the transparency. The following web sites shows the water vapor that affects transparency over the United States. Try here and here.

Seeing is an estimate of how steady the atmosphere is. There are two scales, both related. One was developed by Eugene Antoniadi, a well-known planetary observer. The second one was developed by the Association of Lunar and Planetary Observers (ALPO).

On Antoniadi's scale a seeing of I corresponds to perfect seeing with steady images even at high magnification; II is intervals of perfect seeing with occasional periods of less stable seeing; III denotes fair seeing with frequent unsteady images so that medium magnifications are used; IV is poor seeing that offers only occasional glimpses of detail; while V is very poor with blurred images even at low power.

On the ALPO scale a seeing of 9-10 corresponds to Antoniadi's seeing of I or perfect seeing; 7-8 on the ALPO scale would be very good seeing corresponding to Antoniadi's II; 5-6 on ALPO scale would be good seeing corresponding to III on Antoniadi's scale; 3-4 on ALPO's scale would be fair seeing corresponding to IV on Antoniadi's scale; while 1-2 on ALPO scale would be poor seeing corresponding to V on Antoniadi's scale. You can use whichever scale you wish as long as you keep track of which one it is.

An easy way to remember is to think of seeing in terms of the highest magnification you can use when observing the planets. If you can employ a magnification of 50x or 60x per inch of aperture or greater and the image is still steady then your seeing would correspond to I on Antoniadi's scale and 9-10 on ALPO's scale, or excellent seeing.

If you can employ similar magnification or a little lower, say between 30x to 40x per inch of aperture, but there are occasional periods of less stable seeing then your seeing would correspond to II on Antoniadi's scale and 7-8 on ALPO's scale, or very good seeing.

If you are able to only employ medium magnifications, say between 20x to 30x per inch of aperture, your seeing would correspond to III on Antoniadi's scale and 5-6 on ALPO's scale, or good seeing.

If you are observing and using between 20x to 30x per inch of aperture or less but only occasional glimpses of detail then your seeing would correspond to IV on Antoniadi's scale and 3-4 on ALPO's scale, or fair seeing.

If your are using low power and only seeing blurred images then you're seeing would correspond to V on Antoniadi's scale and 1-2 on ALPO's scale, or poor seeing.

Jupiter, October 13, 1999 2:40 - 3:00 UT, seeing 8 - 9, transparency 5.5. System I Central Meridian 186.6 degrees, System II Central Meridian 56.4 degrees. Astro-Physics 5.1" f/8.35 EDF refractor on homemade Dobsonian-style mount. Magnification 308x with Baader binoviewer.

Some general considerations about local seeing effects. Natural vegetation, such as a grassy field, make a good observing location. Manmade objects, such as asphalt parking lots, streets, and buildings, absorb solar radiation during the day, and release it slowly at night. This can adversely affect seeing.

When possible, try to observe when the planet is 45 degrees or higher above the horizon as you will be looking through less atmosphere and the seeing tends to be better. Also, the seeing is often steady right after sunset, as well as after midnight as much of the heat that has been absorbed by the surface of the earth has been released by then. This can be particularly true around sunrise.

As a general rule, when the jet stream is located over your observing area, the seeing is not very good. The same holds true for high altitude air turbulence. There are a couple of websites that can give you idea of the position of the jet stream, as well as turbulence. Try:

Air Turbulence Potential

Seeing Forecast

Before a cold front comes through the seeing can be good, but gets worse once it passes. As the high pressure system moves over your location and begins to move away the transparency starts to drop but the seeing can get better. The seeing is often poor after a cold front has passed through your observing area.

As a general guide, in the Northern Hemisphere when the wind flow is from the north or northwest, it brings colder and drier air with it, which is unstable as the cold air moves over the warmer surface (depending upon where you live). This is particularly true during the day, and it may take time for this instability to settle down at night. During the sky often appears to be blue down to the horizon. This suggests that the transparency that night will be good, but the seeing may not be. On such nights it may be better to observe deep-sky objects (assuming the light from the moon will not interfere) since the seeing for the planets may not be very good. These kinds of conditions are more common during the winter months.

When the wind flow is from the southwest or south, it brings warmer and more moist air with it (once again depending upon where you live). The sky often appears to have more of a milky appearance to it, particularly near the horizon. This suggests that the transparency that night will not be as good, but the seeing may be. On such nights it may be good for observing the moon and planets, but not necessarily for observing faint detail in deep-sky objects. These kinds of conditions are more common during the summer months.

Jupiter, October 17, 1987, 0:15 - 0:40 UT, seeing 3-4 (fair-good), transparency 5. System I Central Meridian 260.7, System II Central Meridian 62.6. Astro-Physics 6" f/9 refractor on Byers 58 equatorial mount. Magnification 172x. Filters used: none.

Some of the best seeing for the planets can occur on warm and hazy summer nights when the transparency is poor, and only the brightest stars are visible. These same kinds of weather conditions can occur during the early fall as well, or in the spring.

Other times when the seeing can be very good is early morning before sunrise when most of the heat absorbed by the surface has been released. Ground fog is another good indicator of a stable atmosphere, but just be careful with dew forming on the telescope optics.

Note that these are general guidelines, and there are times when the seeing can be good even when the transparency is good, as there are times when the transparency is poor and the seeing is poor as well.

Another thing to keep in mind is that simply looking to see with the unaided eye how much the stars are twinkling at night does not always give you an idea of how stable the seeing is for observing the planets through the telescope. I have seen some nights where to the unaided eye the stars were twinkling quite a bit, but the seeing was actually pretty good for the planets. On other nights the stars didn't seem to be twinkling much at all to the unaided eye but the seeing was poor for the planets.

Making a Drawing

Before you begin your drawing take some time to study the planet and get acclimated with what you are seeing. This would include the features visible and the colors of the planet. How much time you spend studying the planet can depend on different factors. This includes how stable the seeing is.

On nights of variable seeing it may take time to clearly see the detail, and you may find it necessary to change magnifications a number of times before you are sure of what you are seeing. On nights of very steady seeing you may start recording the detail right away. I generally use as high as magnification as the seeing permits and allows me to be sure that what I am seeing is accurate. I will often increase magnification to resolve the finer details.

Saturn, September 14, 1997, 5:05 - 5:55 UT, seeing 9 (0 worst, 10 best), transparency 2. Astro-Physics 7.1" f/9 EDT refractor on a homemade Dobsonian-style mount. Magnification 270 - 405x with Clave prism diagonal. The inner portion of B-Ring appeared shaded, and composed of very fine lines or spokes. I was not sure what these very fine lines or spokes were, as they did not look like spokes I had seen in books or photographs, which were usually further out in the B-Ring. Seven months later while reading the April 1998 issue of Sky and Telescope noted these fines lines that I saw were similar to those shown in a drawing made by Phillip Sidney Coolidge at Harvard Observatory using a 15" achromatic refractor back in the 1850's.

Another factor that will influence how long you study the planet before beginning your sketch is how quickly it rotates. For example Jupiter rotates quickly, and if very interesting detail is visible you may decide to begin your sketch after just a few minutes of studying it. Mars rotates more slowly so there is more time to study it. Saturn rotates almost as fast as Jupiter but since there is a haze layer in Saturn's upper atmosphere it isn't as easy to note its rotation, and its features are often subdued. This haze layer also makes Saturn appear much less colorful than Jupiter's atmosphere.

Depending upon the seeing conditions, and the features visible on a planet, I may spend 20 minutes or more studying it before I begin a sketch.

Saturn, December 8, 2002, 4:15 - 6:20 UT, seeing 5 - 7 (good - very good) transparency 3. Astro-Physics 7.1" f/9 EDT refractor on homemade Dobsonian-style mount. Magnification 275x - 344 with Baader binoviewer. The Crepe Ring was prominent and visible in front of the globe. On the preceding (or left) ansae of the B-Ring several spokes were visible, while on the following ansae four spokes were visible. These were more prominent than those on the preceding ansae. Outside of the Encke Minima on the following or right ansae four radial spokes were visible, with brighter areas appearing between them. Two additional bright areas were visible on the left or preceding ansae.

Once you feel you have a good idea of the detail visible you can begin your sketch. At this point you may be thinking that yes you see a few features but it doesn't seem worth making a drawing. Make one anyway, and when you are recording the features ask yourself a few questions:

1.) Do all of these features appear to be the same size?

2.) Do all of these features appear to have the same height and width?

3.) Do all of these features appear to have the same tone, or are some darker or lighter then others?

4.) Do all of these features appear to have a smooth outline, or are there irregularities visible?

5.) Are there any differences in color?

Here are some sample drawings of Jupiter, and a few easy steps that can be used to complete your drawing:

Step 1 - Note the date and time on your form, seeing and transparency, as well as the telescope, magnification and any filters used. Color filters can be used to enhance planetary detail. Here are some of the more common filters used for the planets listed by their Wratten numbers. For Jupiter and Saturn, 80A (light blue), and 30 (magenta). For Mars 11 (yellow), 21 (orange), 23A and 25 (red), and 58 (green), and 30 (magenta).

Step 2 - Sketch the outlines of all of the detail you can see. Note in this example I am using color pencils but you can use lead pencils:

Step 3 - To help position the planetary features you see on your sketch correctly you can try thinking of where these features begin and end in terms of a clock face. As an example, a particular belt on Jupiter may start at the 2 o'clock position and extend across to the 10 o'clock position. You can use the same method to determine how wide a belt appears;

Step 4 - Now shade in the detail. If a feature, such as a belt on Jupiter, appears darker then another one, try to show that in your drawing:

Step 5 - Record the time you finished your drawing.

Once you are finished making your drawing and are back inside you may pull out a magazine with some nice images of Jupiter and think to yourself that your drawing doesn't look anything like that. But don't feel bad because my first drawings didn't either. My first drawing of Jupiter looked more like a yellow tennis ball with a few brown lines on it.

The next time you go out to observe make another drawing. Over time as you make more drawings you will find that indeed you can see more detail. These drawing will serve as a permanent record of how the planet appeared to you during a particular year.

To learn more about the planetary detail you are seeing click here for Venus Nomenclature, Mars Nomenclature, Jupiter Nomenclature, and Saturn Nomenclature. If you click on the arrows at the bottom of each of these pages you will be taken to other sketches I have made of the planets.

I found that as I made drawings of the planets and began to see more detail that I felt I got to know the planetary features better. I would consult a book and learn what the belts and features on Jupiter were called, and what Saturn's rings were composed of.

Also I began to look forward to observing the planets each new season. For, not only was I beginning to see more detail as I trained my eye more, but I learned also that features on the planets would be change from year to year as well. Night after night I would look forward to see if new feature would become prominent on the surface of Mars, or some change would take place in Jupiter belts, or some transitory detail in Saturn's rings would present itself.

Of course, if you mention that you have an interest in the planets to some people they may get the wrong idea. When I was in high school I went over to visit a friend one day and when I walked into the kitchen a friend of his mom's turned to me and said, "So I hear your into astrology. Tell me about myself!" I was caught a little of guard as I never had anyone confuse astronomy with astrology before, so simply replied, "No, I'm interested in astronomy, such as telescopes and observing." "Oh", she replied, "Well, your into the wrong thing then." If the same thing happened today I would have a few choice words in reply, but at the time just tried to be diplomatic.

Drawing Deep-Sky Objects and Comets

The same techniques that are used to record detail of the planets can be used to record detail of deep-sky objects. Here are a few examples.

The above sketch is not of the planet Saturn, but rather of the The Saturn Nebula, which is a small, bright planetary nebula located in the constellation of Aquarius. September 28, 2002, 9:50 - 10:40 PM, seeing 4 - 5 (fair - good), transparency 4.9. Astro-Physics 7.1" f/9 EDT refractor on homemade Dobsonian-style mount. Magnification 162x.

The above sketch is of Saturn near M1, the Crab Nebula. Through the eyepiece the nebula is relatively bright, with an irregular shape to it and diffuse near the edge, with a slightly brighter inner portion that resembled a Z shape. The nebula appears light green in color. Saturn showed a light yellow Equatorial Zone, a tan South Tropical Zone, and a green South Polar Region. The Cassini Division was visible on both ansae and in front of the globe, as was the Crepe Ring, although these features do not show up well in the sketch when it was scanned in. Four moons were visible nearby including Titan, Tethys, Dione, and Rhea. December 29, 2002 8:55 PM - 9:45 PM, seeing 4-5, transparency 4.5. South is at the bottom. Astro-Physics 5.1" f/8.35 EDF refractor on homemade Dobsonian-style mount. Magnification 68x-91x.

The Veil Nebula, September 5, 2002, 9:20 - 11:05 PM, seeing 5, transparency 5.3. Also September 6-7, 2002, 9:50 PM - 12:35 AM, seeing 5, transparency 5.5. 90mm f/5 refractor on alt-az mount. Magnification 15x, 21x, and 28x used with a Lumicon OIII filter.

Comet Ikeya Zhang, April 11, 2002, 7:55-8:40 UT, seeing 5, transparency 5.0 with a few high clouds. Astro-Physics 5.1" f/8.35 EDF refractor on homemade Dobsonian-style mount. Magnification 115x, field of view approximately 0.7 degrees. North is to the upper left in this drawing.

Comet 17P Holmes, October 29th, 2007, 3:30 - 4:30 UT. Clear skies with the limiting magnitude around 4.0 with the light of the Moon a couple days past full. Seeing 5 - 6 (fair - good). TMB Optical 175mm f/8 refractor on a homemade Dobsonian-style mount. Magnification 88x-156x, field of view approximately .65 degrees. I estimated the comet to be around magnitude 2.3.

Keeping a Log Book

My other suggestion would be that in addition to making drawings at the eyepiece is to keep a log of your observations. Record information like the weather conditions, such as seeing and transparency, date and time of observation, telescope and eyepieces used, and anything else that you wish to record. It can be something as simple as writing down your observations in a log book, or taking notes at the eyepiece and transferring them to a computer when you get back inside. Your notes may include how well a particular eyepiece of filter worked with the telescope, how a new accessory performed, and success or failure in finding deep-sky objects or seeing some elusive planetary feature.

Keeping a log book may seem like extra work, but over time these notes will become invaluable to you, as you will begin to correlate how the combination of telescope aperture, magnification, filters, and weather conditions are best for observing the planets and moon or deep-sky objects. This is particularly true when you attend star parties and get a chance to try telescopes or eyepieces that you don't own yourself. I enjoy reading through observing logs that I made years ago to see the kind of detail I saw in objects with telescopes I owned back then, versus the kind of detail I see today with my current telescope equipment.

Summary

Making a drawing at the eyepiece one of the best ways to learn to see more detail. This holds true not just for the planets or moon, but for deep-sky objects as well.

This is because you are training your eye to see more detail. The best way to begin is to start out making simple sketches, and then as your interest grows make more detailed drawings. At the same time you will be making a permanent record of how the object appeared during that particular observing session. Keeping a logbook is another good idea, as it gives you a permanent written record of your observing sessions.

In addition, you may record long term changes on the planets, such as I did for the shrinking of Jupiter's Great Red Spot.

After a while you may find that you enjoy making drawings and you may decide to concentrate on making sketches of a particular subject, such as the planets, the moon, or deep-sky objects. One such example is a book by Stephen James O'Meara entitled The Messier Objects. In the book he made detailed drawings of all of all 109 Messier objects using a 4" refractor. The detail in these drawings is remarkable. In part this is because of his renowned observing skills, and also because he made these observations from a very dark sky location.

However, it shows also what a patient and persistent observer can do with a telescope of relatively modest aperture and who is willing to spend time studying an object and making a sketch of it to see the faintest detail visible. There are times when we observe an object with our telescopes and think, "Yes, it looks nice in this aperture telescope, but I wish I had a larger aperture telescope so I could see more." By making drawings, we can learn to see more with the telescope equipment that we own, and come to appreciate the wonders of the universe even more.


Article 2000 - 2014, Eric Jamison, All rights reserved. May not be used without written permission of the author.

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