How to make astronomical sketches

Astronomical sketching is becoming ever more popular, and with good reason too. Not only is it great fun and does it give additional value to the extraordinary hobby that astronomy is, it's also the best way to learn how to observe. Astronomical objects are usually faint or have details that can only be discerned through a good adaptation to darkness, patience and experience. When you're sketching such an object, you're forced to concentrate on the image but yet relaxed enough to let the details leap out at you. My astronomy teacher 35 years ago therefore told me that in order to learn how to observe one should start sketching. And so I did and I'm still extremely happy for the advice that he gave me as a kid. 

In order to give everyone a hand at sketching, I'm creating a series of videos in which I'll reveal all of my little secrets. Of course, They'll only contain my personal techniques whereas there are just as many techniques as there are sketchers. But nevertheless I hope that my videos will be useful to everyone and I sincerely hope that you'll enjoy them.

Here's the first about preparation. I'm afraid that the second will only follow in September due to... holidays. :-) But I'll keep you informed through my blog whenever a new video's released.

Happy viewing!

Saturn, the extraordinary planet

Ever since Galileo pointed his little telescope to Saturn, the 6th planet of our Solar System has always been observed with marvel and wonder due to its extensive ring system. Saturn's not the only planet with rings. The first probes that were sent to the outer Solar Sytem in the seventies, discovered that also Jupiter, Uranus and Neptune have a number of rings, albeit not nearly as big and spectacular as Saturn's of course. The ring system looks very impressive and is indeed 282.000km across. However, at most places it's only 30ft thick (!) apart from a few areas where the thickness increases to a few kilometres. If Saturn were a ball with a diameter of 1m, the rings would actually be 10.000 times thinner than a razor blade! Their origin is still uncertain and the most prominent theories suggest that they are the remains of a former moon that got too close to the giant planet and was ripped apart by tidal forces, or that it's just debris left over from the time that the planet was formed. They consist of water ice particles, with some traces of rocky elements, ranging from 1cm to 10m in size. Next year the rings are at their most visible because they'll be completely slanted towards us, and so they already show well on the sketch that I've made. But since Saturn's tilted, just like Earth, the angle at which we see the rings changes over a 28-year period (the time it takes Saturn to orbit the Sun). In 2009 we saw the rings edge-on and as such they were difficult to see, a phenomenon which will happen again in 2025. The ring system is extremely complex with different densities and even gaps. The most famous "gap" is the Cassini Division, which you can see clearly on the sketch and is easily visible already with a small telescope. It's not really a gap but just a region of lesser density, some 4.800km wide. The Encke Division, nearer to the edge, was hardly visible during this observation due to the extremely poor conditions. It's a 325km gap caused by a tiny moon, Pan, that orbits within it! 

Saturn itself is the second-largest planet of our Solar System, with a diameter roughly nine times that of Earth. Though it's mainly composed of gas, for the largest part hydrogen and helium, and hence its density's a lot less, resulting in a mass about 95 times that of our planet. Ammonia crystals in its upper atmosphere are responsible for the pale yellow hue. Wind speeds can reach 1.800km/h, which is much faster than the speed of sound and even faster than the hurricanes on Jupiter, but not as fast as the winds on Neptune. 

No less than 62 moons have been identified, excluding the hundreds of moonlets that hide within the rings. Titan, the largest of which, can also easily be spotted with a small telescope or binoculars and is seen here on the far right. It is the second largest moon in our Solar System, after Jupiter's Ganymede and it's even much bigger than Mercury (sorry, Astrologists), though not as massive. What's more interesting, Titan's the only moon known to have a dense atmosphere and it's the only place apart from Earth where stable bodies of surface liquid have been found, albeit liquid methane and ethane instead of water. But Titan's methane cycle is very similar to the water cycle on Earth and also its general aspect is thought to be the same, with oceans, dunes, rivers and mountains. Unfortunately, its thick and cloudy nitrogen atmosphere (denser than Earth's!) prevents the surface from being examined visually so we had to use infrared and radar to discover it. Given the presence of many complex molecules and the conditions similar to those on primordial Earth, many scientists have highlighted Titan as a candidate for extraterrestrial life. Although there are many obstacles such as the extremely cold surface temperature of -179°C and the absence of CO2. In 2004 a simple probe was sent down to its surface which transmitted a lot of interesting readings back to Earth. Scientists hope to send a more powerful probe to Titan within the next decade.

In total I could see 5 moons, less than I could expect with my new 18" binoscope, but as I already mentioned, the conditions were terrible. I was actually doing a test run of the telescope and still had to complete a lot of work on the correct alignment of the two telescope tubes. Therefore I chose to observe from an illuminated car park with an asphalt surface after a very hot day. Probably the worst place one could choose for astronomical observing because asphalt absorbs a lot of heat and re-emits it during the night, causing a lot of horrible heat turbulences. But now the telescope's finally ready for use and I can't wait to take it up in the mountains. Be ready for more sketches soon! 

The power of star formation

While I'm still adjusting my new binoscope, I'd like to present an older sketch but with a very interesting subject. The faint little patch you see here in the drawing's centre is a nebula denominated NGC6857. It's an emission nebula, which means that it doesn't just reflect the light of the surrounding stars but that it's heated up so much that it begins to emit light on its own. This particular nebula is part of another gigantic star forming region in our galaxy but much further away from us than for instance the Orion nebula complex. The distance of NGC6857 is estimated at 25.000 lightyears, which is at almost one quarter of the total diameter of our galaxy. The sketch was made with my good old 18" Dobsonian telescope so you can guess that it's not a particularly easy object and as such reserved for larger telescopes. You can find it in the heart of the constellation of Cygnus, near the rim of the Great Rift, a large, dark cloud of dust that can easily be seen with the naked eye (under a dark sky) and which seems to cut the Milky Way horizontally in two. As I mention it, some darker patches were also visible in the telescope view as I've reflected in the sketch. You have to imagine that the brighter background glow is caused by millions of stars that are so far away that they can't be resolved through an amateur telescope. The darker patches are clouds of dust that block the light from the stars behind them. 

Returning to our nebula, the odd thing about it is that it's also a very powerful maser; one of several in the area. A maser is quite similar to a laser, but emitting a beam of microwaves instead of light. Surprisingly, the most common molecules responsible for this are water and methanol, apart from other OH radicals and silicon monoxide. Radiation in the hot star forming cloud excites these molecules up to a point that the majority of them turns into a higher energy state. In turn they start to amplify microwave emissions which are by far the strongest emissions that we observe in the entire radio spectrum. Sometimes listening to our universe can be more exciting than looking at it!

The Bino-Dobson

As I already explained, one of the main problems that we, visual astronomy observers, have to confront is the desire to see more. Moving to a dark sky always helps a lot but even then our hunger for more can't be satisfied fully. Why can't I perceive that dustlane in that distant galaxy while my friend with his bigger telescope can? Why doesn't that nebula reveal those delicate filaments which I've seen on a photo? 

So in the end, many of us take the great leap forward and sell our telescopes in order to buy a bigger one. Which will keep us happy for a while until we're once more disappointed because also that bigger scope turns out to have its limits. At this point the astronomy community becomes divided. There's one half that resigns because of financial or practical reasons. Even if they can afford an even bigger telescope, where can they store it? Or how would it still be possible to transport such a monster to their preferred observation site? Or what would be the sense of buying something so big that it takes an hour to set up?

Then there is the other half. Those that never give in, regardless of the cost or practicality. They'd give an arm and a leg just to see that extra nebula filament with their own eyes. Yes, I have to confess... I'm part of this group, the group with unstoppable "aperture fever" (referring to the aperture of the telescope, or in other words the size of its lens or mirror). I used to own a respectable home-built 18" (46cm) Dobsonian telescope, which has given me many satisfactions for almost 10 years. But unfortunately it wasn't enough. Moreover, I experienced ever greater difficulties observing with one eye only. It's terribly tiresome and doesn't give you nearly as many satisfactions as observing with both eyes, such as with binoculars. The feeling of immersion, really "being there", floating through space without limits or boundaries that binocular observation offers can never be obtained with a single eyepiece, even the fancy ones with their 100° field of view. I've experimented for many years with all kinds of binoviewers, which split the light beam of a telescope in two so you can look with both eyes. I've used the cheap ones, the expensive Denk II and I've even been the proud owner of a gigantic 2" Siebert. In the end, none of them, not even the 2" model, satisfied me because they always resulted in a compromise with too many disadvantages such as light loss (even with the 2"!) and an undesired magnification increase. 

Hence the great leap forward: a binoscope. This is in fact two 18" Dobsonian reflectors glued together as it were, which you can use with both eyes like true binoculars, albeit that they are a little bit bigger. This time no more compromises and the true performance of a 25" to even 32" (faint objects) telescope! The only drawback is its size and above all its complexity to use. Let me make this clear: this is NO telescope for newbies or for people who don't like to collimate or fiddle with their telescope. This must be the most complex telescope design on the amateur market and I can assure you that aligning all of the mirrors is not child's play. But it has its compensations, such as an image so bright, rich, infinite, contrasty and even 3D-like that no other telescope could possibly compete. Perhaps I've finally found the telescope that will cure my severe case of aperture fever? Well, if this one won't, I don't think any telescope would. 

To conclude I'd like to express my sincere thanks to Mr. Otte, the builder of this amazing instrument, for his incredible craftsmanship, his personal and dedicated service and last but not least his friendship. It's a real pity that my scope was the last one that he's built and that he's giving up his telescope manufacturing company because it's only because of men like him that we amateur astronomers can truly enjoy the sight of the heavens.

 

 

Don't forget the sun!

Most people believe that you can only do astronomy at night and preferably in a remote place where the stars still form a sparkling blanket in the sky. Hence the rather awkward reputation that many astronomy enthusiasts enjoy. But that couldn't be further from the truth! 

Studying and analising the stars is extremely difficult because they're so mind-bogglingly distant. To give you an idea of what I'm talking about, imagine that the Earth's the size of a peanut. In that case the nearest star would be... 20.000 miles away! So if we want to study the physics and dynamics of a star, why would we go through all that trouble of studying such remote objects when we've got a very nice example threehundred thousand times closer to us? As you all know, the Sun is a star. Not a particularly bright one and certainly not a very big one I might add, but yet a very stable, middle-aged example. So if we understand our Sun, we can also understand other stars, even those that reside in the most distant galaxies. Therefore the observation of our Sun is a very important part of modern-day astronomy and also many amateurs have special equipment to observe our star in a safe way. Please, do not observe the sun with the unprotected eye! The story about Galileo losing his sight after having observed the sun is nothing but a hoax and in reality he became blind of cataracts. But if I were you I wouldn't try to find out what the sun looks like through an unfiltered telescope which can concentrate sunlight a thousandfold! However, there are plenty of methods and instruments out there which allow you to observe the sun in all safety. Unfortunately I haven't got them. But today I'd like to share the work of a friend who has.

Iain is a British astronomer with decades of experience and just like me he's a keen sketcher. In fact, I often see him as a source of inspiration so I regard it an honour when he allowed me to post his work here. Recently Iain published a 60-frame animation of 6 different sketches showing a spectacular solar prominence. A prominence is an ejection of gas from the sun's atmosphere, often loop-shaped and reaching hundreds of thousands of miles into space. Indeed, the Earth would look tiny in respect! The process that generates them still isn't completely understood but usually they form within a day's time and they may persist for weeks or even months. The animation shows the changes of the prominence in the period of one day:

I'd also like to invite you to visit Iain's stunning blog on which you can also find some amazing solar photographs and photo animations he made, apart from his beautiful deep-sky work:

http://fouragesofsand.blogspot.it/

Enjoy!

And now I'll be gone for a couple of weeks because... I'm getting married next Friday. :-) But don't worry... I'll be back!

The wealthy charioteer

Auriga is a very rich constellation because the Milky Way runs through it and therefore it houses many star clusters and nebulas. Although it's interesting to note that it lies exactly on the opposite side of the centre of our galaxy! Its Latin name means "charioteer" as it is often identified with the legendary Athenian hero Erichtonios, who was credited with the invention of the four-horse chariot. 

When you take your binoculars and point it at Auriga, you'll easily notice why even ordinary field binos make a perfect instrument for observing the night's sky. Here's a combination of three views through my 100mm binoculars, showing you three of the most famous star clusters: M37 (on the left), M36 (centre) and M38 (on the right). I already posted a zoomed-in sketch of M37 here which was made with my old 18" telescope, so now you can make a comparison between a telescope and binoculars. As you can see, both instruments are perfectly complementary because they're doing a different job: the binos offer a wide field of view and allow you to travel across the heavens, whereas the telescope zooms in on a particular object and shows you the smallest details. 

As you'll remember, M37 is already a fairly old star cluster, with an estimated age between 400 and 550 million years, and yet it is extraordinarily rich with over 500 identified members. Usually star clusters break up as they grow older, torn apart as they are by the tidal forces of our galaxy, and the stars each go their own way. But M37 on the other hand has remained extremely compact, probably because it's such a large and compact cluster and the gravitational pull of the group is strong enough to counter the pull from our galaxy.

M36 is much younger than its neighbour, estimated 25 million years, and it contains a lot less stars as well - about 60. But due to its young age the stars are still much hotter and therefore this smaller cluster, even though it lies at roughly the same distance (4.100 lightyears), looks slightly brighter to us. If it were closer, it would actually very much resemble the famous Pleiades. 

And then there's M38. As far as age is concerned, it lies exactly between the other two: 220 million years. It contains twice the number of stars of M36 but here our galaxy's gravitational influence is evident and it's structure has become very irregular. Most observers describe it as an oblique cross, rather than it having a standard circular shape. With time it will dissipate ever more until the cluster will be gone completely.

But this isn't all! If you look carefully, the three have yet another companion, albeit a much smaller one, denominated NGC1907. It lies just a tad to the bottom-left of M38... can you spot it? This little cluster contains only 30 members because most of its stars have already gone their own way. It's about the same age as M37 so here you see what usually happens to older star clusters. Scientists have also measured some interaction with nearby M38, although they were born in different regions of our galaxy and obviously have a different age as well. So probably we'll have to conclude that the pair are just having a coincidental fly-by. 

Mirach's Ghost

Mirach is the brightest star in the constellation of Andromeda. It has a deep red colour indicating that it's cooled down significantly as it expanded to a size roughly 100 times our Sun towards the end of its life. Its colour is so stable that it has served as one of the references for stellar classification. Apart from this, you wouldn't expect anything particular about it. It's just an old giant star without any characteristics that would make it worthwhile dedicating a sketch to it. Well, at first sight anyway.

But hoho... Wait a minute! What's that faint patch on the right of the field of view? Yes, that's right! It's a galaxy! It's not all that easy to see because bright Mirach is slightly blinding you and that's why they nicknamed it "Mirach's Ghost". Now you see it, now you don't. But when you let your eyes adjust to the field of view it will certainly leap out at you, even through not very large telescopes. 

NGC404, its scientific name, is a dwarf galaxy at the reasonably close distance of 10 million lightyears. Yet, it is classified as a so-called "field galaxy" because it doesn't seem to have any gravitational interaction with other galaxies, even though it's quite near to our local group. The poor little thing just lies there, completely isolated and very inactive. Like other early-type galaxies such as M105, there's very little star formation going on and it appears to be slowly dying. Scientists believe that at some point it had a spiral structure and hence was very active but that a dramatic merger with a companion, some 1 billion years ago, reduced it to its almost vegetative state. Very few details can be discerned and especially through amateur telescopes you shouldn't expect to see more than a blurry little patch. Analysis revealed however that it has a pair of haloes of neutral hydrogen and that it houses a massive black hole too. 

So all in all, the combination of two seemingly uninteresting objects, Mirach and NGC404, still make a wonderful observation. Especially since both the star and the galaxy have a lot in common: both have reached the end of their life and both display very little activity. Astronomy isn't always about spectacles, cataclysms and dazzling star fields. Sometimes, something very simple can prove to be a beautiful tableau.