The view of the celestial sky

2. The view of the starlit sky

What I see, I believe…

To our eyes the earth appears as a disk, over which is inverted the sky hemisphere. The earth is however in reality a small, round planet. The sky is not a hemisphere, as accepted in earlier times, but surrounds the earth on all sides. In one period of approximately 24 hours the earth rotates once around its axis. The continents lying on the surface of our planet are turned to face the sun for part of this period, for the remainder they are turned away from the sun. For us human beings this results in the change between day and night results. If one observes the sky on a clear night over a period of time, then one sees that the stars do not stand still. They rise up in the east and set again in the west. In earlier time humans concluded from the fact that the visible vault of the heavens formed itself into a hollow ball beneath the earth disk, from which the celestial objects rise and set again.

As the stars, with some exceptions, do not change their position and the brightness relative to each other one, it was thought that the stars were fixed to this ball and therefore gave them the Latin name: stellae fixae).

How large the sky ball was nobody could determine but it was considered to be immeasurably large. Humans imagined themselves to be always exactly in the centre of the ball, regardless of, at the exact place they were on earth.

… and nevertheless it rotates

It took centuries before people recognized the fact that the stars do not rotate around the earth – but that the earth itself rotates in space around its polar axis.

The stars seem to move in the sky, because the earth rotates around its own axis. This rotation causes certain parts of the heavens to become visible to the observer every 24 hours. (24 hrs: the earth needs 24 hrs for one complete revolution).

By day it can be seen that, due to the earth’s rotation, the sun appears to rise in the eastern horizon, stays in the sky for some hours and then again apparently goes down below the western horizon. At night one sees the apparent movement of the stars. There is not just the sun rise and sunset. There is exactly the same for the rising and setting of the moon and also for the stars and planets we speak of rising and setting. That naturally applies to all celestial objects.



There is a choice of different optical instruments

If we start today on the road to observing the heavens, then two questions arise: “What do I want to see? “ and “How detailed will I see it?”. There are different possibilities for observing the stars. One can undertake the observation with the naked eye and for example explore constellations or shooting stars, or pick up a pair of binoculars and explore the constellations and the planets. To see the objects more closely and to explore planets, comets and galaxies, you need a proper, large telescope. If however you wish to observe the land as well as the starlit sky you can still reach for your binoculars or Spotting scope. Lens telescopes are also suitable with special accessories for land observation.

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2.1 Observing with the naked eye

If you are out and about during the evening, and look at the sky with the naked eye, then even as a lay person you will already recognise some remarkable celestial objects. Depending upon how darkly it really is, that is to say how strongly the night is “polluted” by city light, you can also notice one or more weakly shining object. If the moon is to be seen, this would naturally be the first to catch the eye. It can frequently even be seen by day or in the early evening before sunset. The moon is the nearest object to us. However if the moon is not to be seen and the skies are crystal clear, one can still clearly identify many other objects. The band within our own galaxy, the Milky Way, is quite easy to recognize. Depending upon the time of year and the time of day the bright star Sirius as well as the planets Venus, Jupiter, Mars and Saturn can be identified. The constellations take up the largest area of the heavens and some constellations which can be recognized very easily can be made out in the sky almost immediately. The interested layman can immediately recognizes one or other of the large conspicuous constellations such as the Great Bear or Orion.

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2.1.1 Observing constellations with the naked eye

The arrangement of the stars in the heavens, spurred the mankind imagination of humans in antiquity to combine the arrangements of stars into pictures. Thus fallen warriors wandered symbolically across the heavens and monsters from the underworld fought with heroes. The signs of the Zodiac also developed in this mythical way. For example the mythological background of Orion is particularly interesting: the warrior hunted the Pleiades, the seven daughters of Atlas. Arthemis sent the scorpion to kill Orion, which it did. Thus Orion sets in the west when his murderer, the scorpion, rises in the east.

Orion, the great bear, the little bear or the W-in the sky (Cassiopeia) are clearly recognisable constellations, which can be quickly found. Orion, for example, is a constellation, which is visible throughout the whole of winter. The constellation seems to give the appearance of an inclined hour glass. The three stars forming the belt of the mythological hunter Orion are the easiest to identify, as he fights in the night sky against the bull (lat. Taurus). One can also soon recognise the stars forming the shoulder, head and foot of Orion.

The great bear is clearly visible for virtually the whole year and is an easily recognizable constellation. It actually looks like a hand cart, a trapezoidal body and a handle. This constellation is a part of the Great Bear.


Observing shooting stars with the naked eye

They were pointed out to us as children, in order to wish for something. They are clearly visible with the naked eye and occur whenever small particles from space enter the earth’s atmosphere and glow due to friction. They can be rock dust, which can vary in size between 2mm and 30cm and above.



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Fig. 5: The constellation Orion (mythical hunter of the Pleiades)

Fig. 6: The constellation of the Big Dipper (also Big Bear)

2.2 Observing with binoculars

With good binoculars many things can be discovered in the sky. Binoculars can be fitted onto a stand using a stative thread. If it is possible to identify several thousand objects just with the naked eye, then it appears that more objects will be found with the binoculars. It is not the increase in the number which makes the difference however, but rather the possibility of magnifying the objects. With good binoculars you are in a position to identify the moons of the planet Jupiter. Take aim at the constellation of Orion, below the stars forming the belt the Orion Nebula M 42 can be observed. This comprises an enormous cloud of inconceivable extent, which consists of cosmic dust and gases and becomes illuminated by UV light shining from the stars.

Our neighbouring galaxy M 31 (fig. 8) can also be recognised as easily with binoculars. No wonder, it extends across the heavens for over five moon diameters. It is a beautiful spiral galaxy of a similar to our own galaxy (the Milky Way).

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Fig. 7: A pair of binoculars of the Porro

2.2.1 Observing planets and moons with binoculars

If you see a bright “star” in the sky, which is not shown on a star map, then it is for certain a planet. The earth is one of nine planets, which all circle the sun. Two of the planets, Mercury and Venus, are closer to the sun than to our Earth. The other planets Mars, Jupiter, Saturn, Venus, Neptune, Uranus and Pluto are further from the sun than our earth.

Five of the planets - Mercury, Venus, Mars, Jupiter and Saturn – can be recognized easily with the naked eye or binoculars. They appear to us like bright stars, until one observes them with binoculars or a telescope. Detailed observations are not however possible with binoculars due to the low magnification.

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2.2.2 Observing deep sky objects with binoculars

If one leafs through astronomical technical periodicals or thro u g h advertising brochures of some telescope dealers, then one inevitably discovers the term “DEEP SKY”. Astronomers call all objects, which are beyond our planetary system, deep sky objects. That is a whole pack of objects of interest, which will open itself to our eyes, when we go on safari equipped with binoculars or telescopes. As we have alre a d y mentioned in the introduction, we are spoiled with multicoloured pictures of bright gas nebula, from the media and advertisements. If a layman hopes to be able to see this colourful display in the binoculars he will be somewhat disappointed at the beginning. The pictures are photographic images requiring long exposure times, which cannot be seen by eye even with the largest telescopes. Naturally one should not be disappointed, because one can still see very much more with binoculars, than with the naked eye. For instance, the eye has a maximum pupil aperture of 8mm. With binoculars with only 50mm aperture the surface, which collects the light, is already large enough for one to still see stars that are 7 times darker, than the faintest stars which can be recognized with the naked eye. This opens up a large selection of interesting objects.

The larger the lens aperture, the more stars are recognizable. But even large apertures are not able to arrange colour images for us. Our brain, which processes the pictures of the retina, has a maximum “exposure time” of a quarter of a second, to compare this time with a photo camera. In order to photograph gas nebulas or galaxies, the cameras on large telescopes are often exposed for several hours. For visual observers at night all cats remain grey.

If one wants to observe double stars and star clusters, here visual observation is usually superior to photography. Beautiful images, which leave sparkling accumulations of stars with the observer, are not reproducible on photographic paper. Here one can savour the astronomic experience in full measure.

In order to come to fully appreciate deep sky objects, one needs as clear and dark night as possible. The astronomer’s enemy here is not only the weather, but often also the moon, which lightens the sky. Clear new moon nights are very well suited, preferably out in the country, remote from civilization. There light contamination due to cities is smallest.

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Fig. 8: Our neighbouring galaxy Andromeda-"Nebula

2.2.3 Every beginning is easy

With deep sky observation, finding your way about the night sky is important. In antiquity the astronomers formed the prominent stars into constellations, which were shaped and given a name, using considerable imagination. The constellations in the northern sky are entirely formed by figures from Greek mythology. If one compares the sky with a globe, then one can compare the constellations with the frontiers. Bright stars can be comparable to large cities. Visiting astronomical objects is possible by searching locally on maps. We use the prominent stars to assist with orientation.

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2.3 Observing with the telescope

Telescopes come in many different versions, sizes and systems. For the beginner in astronomy it is often not easy to choose the correct model. A n experienced astronomer once said: “Each telescope has its own sky”– and this sentence is to be only underlined. The focal length and/or the diameter of the objective/reflector of a telescope are not crucial – rather that the equipment is used within its optical limits. Basically it can be said that for the beginner a smaller and lighter Refractor (lens telescope) is most appropriate. Larger models are appropriate for the advanced amateur astronomer, since the stru c t u re and the handling presuppose some experience. However a small lens telescope and also a small reflecting telescope are both quickly set up in the garden and one can immediately start observing the sky. Compared to binoculars it is possible to observe m o re objects in the sky with the telescope. If thousands of objects could be seen with binoculars, then there are a hundred thousand celestial objects which could be seen through a telescope. In addition, it is not only the unbelievable number of objects that make a telescope interesting to use. The possibility of collecting a much larger quantity of light with the telescope, with allows selected objects to be observed in far greater detail demonstrates the variety in our universe.

There are many different reasons for using a telescope. A lens telescope can even be used for land observations. A whole range of ideas for observation are offered, which can also be seen with binoculars: mountain ranges, the animal world, forest and game and even sporting events are possible. Similarly, with celestial objects many interesting goals are at our disposal. Beginning with our earth and the moon, then the planets of our solar system, up to the globular star clusters, planetary nebulae, gas clouds and galaxies in deep space, an almost inexhaustible variety is offered to us.

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Fig. 9: A lens telescope of the Fraunhofer Achromat type.

Fig. 10: A reflecting telescope of the Newtonian reflector type.

2.4 The moon

The moon is the largest and brightest object which we see in the night sky. It has a magnitude of – 12.5 mag. The moon with its craters apparently changes its shape, position and brightness from night to night and is therefore a very worthwhile object to observe. The moon does not radiate own light. It only reflects the light of the sun to the earth. It is the closest neighbour in the universe to the earth and is “only” 384,000Kms distantce away , it is about a quarter of the earth’s size and developed somewhat later than the earth, i.e. approximately 3.9 billion years ago.

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2.4.1 The phases of the moon

The moon orbits the earth. During the orbit different reflections of the sunlight are noticed on earth. The moon goes through these phases within 29 1/2 days. Daily papers or weather pages on the internet often publish the current phase of the moon. The individual phases of the moon are designated as follows:

Neumond (nicht sichtbar)New moon (not visible)
zunehmender MondWaxing moon
VollmondFull moon
abnehmender MondWaning moon

Since the moon rises and sets 52 minutes later each day, appropriate phases of the moon are visible at different times of the day and night. The invisible new moon is a day phase and the full moon can be seen throughout the whole night. The waxing phase can be best observed in the evening and the waning phase best after midnight.

Because of its independent movement, the moon travels much faster eastwards between the stars than the sun, so that it “overtakes” it at regular intervals. This period is called the synodic month and takes 29 days 12 hours 44 minutes. The moon’s phases are the result of its faster movement.

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2.4.2 The other side of the moon

If you observe the moon, you will soon realise that only one side of the moon is visible, because only one side of the moon is turned towards the earth. Until 1959 nobody had seen the far side of the moon – in that year a Russian, unmanned spacecraft orbited the moon and sent radio-photograms of the moon back to the earth.

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2.4.3 The moon map

The moon map on page 12/13 shows the most important objects which are visible on the moon. In this map north is at the top - i.e. the moon appears to the observer exactly the same as it is seen with the naked eye or with binoculars.

With many telescopes the image appears standing “on its head” and inverted, then naturally the south is at the top. On many moon maps therefore the moon is shown as it is seen in such telescopes.

Many description of objects on the moon originate from Latin or English. On the moon map Latin names are shown since these are mainly used by astronomers.

To start with the large number of lunarobjects identified is confusing for the observer, but after a while you will certainly find your way about the moon. Why not go for a “moon walk”?

Close-up photographs of the lunar surface are also aids to observation. There are many books and even moon globes of various types and sizes which can also be bought in shops that specialise in such items.

In order to identify all existing moon objects, it is useful to observe the earth’s satellite in all the moon phases. The objects on the bright/dark line (terminator) are particularly suitable for observing by means of the telescope or binoculars because this zone is very rich in contrasts. The light-dark line is not exactly straight, since it leads across many crates, mountains, valleys and seas. With a full moon observation is less satisfactory, because the sunlight radiates over all objects (no shadowing).

The greater the magnification of your telescope, the more objects you will be able to see on the lunar surface. Very good observations are also possible with good binoculars. Spotting scopes are also suitable for the observation of the moon.

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The moon map shows the most important objects

2.4.4 Maria (lat. seas)

These dark areas are the special features of the moon. Together they result in “the face of the man in the moon”. Former astronomers in ancient times believed that these were seas or oceans, but in reality they are flat are a s of dark, volcanic rock. When the moon was formed they really were seas, seas of liquid lava.

Fig. 11 The smooth surfaces were indeed once seas: made of lava!

2.4.5 Mare

(Plural lat. Maria) is the Latin name for seas. Some Maria are round, others have an irregular shape.

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2.4.6 Craters

Circular depressions in the lunar surface are called craters. They often appear very deep to the observer– but in reality are not however. Craters are bordered by circular barriers and many have a small peak (central peak) in the centre. Some craters are circular, others on the sides of the moon appear oval - an optical illusion, caused by the spherical shape of the moon. The craters resulted from the impact of meteorites on the lunar surface.

Fig. 12: Our moon is covered with craters.

2.4.7 Jet Craters

Jet craters can be seen very well with a full moon, because their surfaces consist of bright, reflective materials. They are produced by very violent impacts of large rock fragments. The jets extend with these craters over h u n d reds of kilometres on the lunar surface. The most remarkable jet crater is called Tycho (after the Danish astronomer Tycho Brahe, 1546 to 1601).

Fig. 13: Violent radiation craters on our moon

Fig. 14: Schematic diagram of our solar system

2.5 Observing the planetary system with the telescope

For many thousands of years humans have observed the sky. They formed the bright stars into constellations and identified the regular appearance of the constellations in the annual rhythm. Celestial objects seemed to be firmly attached to the firmament and did not alter their positions relative to each other. There were other celestial objects, which altered their position within the constellations. One differentiated the planets from the fixed stars and stars which appeared to change their position. The planets always follow their own, self-willed paths through the signs of the Zodiac, in which also the sun and the moon move, however more or less chaotically, when viewed from the earth. The mystery of their paths was solved by Johannes Kepler (1571 to 1630), who set the sun at the centre of our solar system and did not make himself many friends at the time for saying so.

At first only five planets were known (Mercury, Venus, Mars, Jupiter and Saturn). Uranus, Neptune and Pluto were only discovered between the 18th and 20th centuries.

As an amateur astronomer you can observe nearly all the planets well, except Pluto, which is much too small and faint. Uranus and Neptune are visible, but mostly do not have any worthwhile objects for the telescope. These planets are too far from us.

If you see a bright “star” in the sky, which is not shown on a pure star map, then for sure it is a planet (Greek. Wanderer). The earth is one of nine planets, which draw their paths in the universe around the sun. Two of the planets, Mercury and Venus are nearer to the sun than our earth. The other planets Mars, Jupiter, Saturn, Venus, Neptune, Uranus and Pluto are further from the sun than our earth.

Pluto was discovered in 1930 by Clyde W. Tombaugh. Astronomers consider whether Pluto is really a planet, because it could also be a moon which has distanced itself from Neptune. Meanwhile numerous objects have been discovered at a similar distance from the sun, which to a large extent have much smaller diameters than Pluto, nevertheless however they possess very similar characteristics. One can therefore assume that there are still many planetoids, which have not yet been discovered.

Five of the planets - Mercury, Venus, Mars, Jupiter and Saturn – can be easily identified with the naked eye or binoculars. They appear to us at first like bright stars - as a pin prick - until they are observed with binoculars or a telescope. Then they appear as segments. In a telescope, a star always appears to us as a small bright point. A planet appears to our eye as a narrow illuminated disk, which with good visibilities appears spatial. If ever you identify a planet in the sky, then you will probably also be able to differentiate it, by eye, from the stars.

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Fig. 15: The course of the ecliptic

2.5.1 Where are the planets?

Planets are not shown on star maps, because they slowly but constantly “pass the stars by”. If you observed a planet over several weeks, its path will become clear to you. One always finds planets in constellations of the signs of the Zodiac. They follow an imaginary line in the sky, which is called the ecliptic. The line of the ecliptic is shown on most star maps.

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2.5.2 Observation of planets

Planets do not radiate their own light, but reflect light from the sun. The reflected light from the planets is very bright, so that they can to be observed in contaminated light in large cities and even with a full moon they are still quite recognisable are. It is however very difficult to make out details of the planet surfaces. The sky must be observed on a very clear night with a large telescope and then you will identify details on Mars or Jupiter. Around Saturn you will see the famous Saturn rings floating. It is nevertheless very interesting to observe the planets with binoculars or with the naked eye tracking their movements through the stars and to note changes in brightness over several days.

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2.5.3 Position of the planets relative to the sun

Since the earth and the other planets move around the sun at differing distances from it, there position relative to each other constantly changes. Sometimes our earth is on the same side of the sun as another planet - another time the earth is on the opposite side to this planet. Astronomers have a name for these different positions. These are shown in the diagram in Fig. 16. Note that the markings for the inside and outside planets differ. With the changing positions of the planets the picture that we can see from the earth changes. For instance, the planets appear to us large and bright when they are close to the earth and / or small and inconspicuously, if they are far from the earth.

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Fig. 16 The position of the inner and outer planets

2.5.4 The planets introduce themselves

Here you will receive a short guided tour through our solar system. We begin our cosmic sightseeing tour with Mercury, the planet next to the sun.

Mercury, the rapid God messenger*

Mercury, the planet next to the sun is clearly visible in the telescope and is an interesting object, however, it does not come very often into the lens. The famous Copernicus (1473 to 1543) is supposed to have regretted on his death bed that he had never come face to face with Mercury. This fate should not happen to us.

Mercury rotates around the sun in only 88 days. It is only visible, if its angular distance to the sun is as large as possible. The maximum that Mercury can be from the sun is 27°. That means that Mercury can best be seen two hours before sunrise or two hours after sunset. Astronomers refer here to the largest eastern or western elongation. If Mercury can be seen by us, this is inferior conjunction, or if it is behind the sun and is not visible this is superior conjunction and it is not visible. Thus a good view of the horizon is indispensable, since Mercury must maintain ground against the bright evening light of the setting sun.

What can we see on Mercury however? During its path within our Earth's orbit around the sun, the phases of Mercury are as recognizable as those of the moon. If Mercury has the largest angular distance from the sun, then a half-lit planet segment can be seen. This is usually difficult to see, since it is usually in the brightest area of the dawn sky. Air turbulence within the area of the horizon makes the observation often generally speaking considerably more difficult, so that one can only observe Mercury’s crescent with difficulty. One cannot identify surface details, although Mercury, beside Mars, is the only planet, whose surface is not wrapped in clouds. As photographs from space probes show, the surface is completely scattered with craters similar to those of our moon.

Fig. 17 Mercury, photographed by the US space probe Mariner 10/NASA

Venus, the bright beautiful one*

A more grateful object is Venus, which is known to us as the bright evening or morning star. Like Mercury, Venus also displays a crescent. Its orbit runs within the earth’s orbit. The average distance to the sun is however twice as large as with Mercury at 108 million kilometres, so that the maximum angular distance to the sun is up to 47°. Venus can be observed four hours before or after sunset. It is substantially easier to find than Mercury because of its brightness.

On clear days it is visible even in the daytime sky. In the telescope Venus impressively displays its crescent to us. Surface details are not recognisable, since Venus is covered by a thick layer of cloud. With a 100mm telescope and high magnification it should be able to identify variations of the cloud cover. Colour filters, used by ambitious planet observers, will be helpful for this.

A completely rare event is the passage of Venus or Mercury across the sun’s surface. Slowly the planet moves over the sun’s disk and creates a mini solar eclipse. Even though other people may not be aware of it, it is a high point among astronomical observations. Impressively one recognises the movement of the planet as a black disk in front of the sun.

NOTE! Very important. You must consider this!
During the observation of the sun the eyes must be protected against the sunlight by suitable sun filters. Directly viewing the sun through a telescope leads to immediate blindness which can not be reversed! Even with the naked eye, viewing the sun is very dangerous.

* NOTE: Please remember when observing Mercury and Venus that these planets are a short distance from the sun. Ensure that you never search for these planets close to or into the sun. Immediate and permanent eye damage leading to blindness will be the consequence.

Fig. 18 Venus, photographed by the US space probe Galileo/NASA

Fig. 19: Rare event: Venus passing in front of the sun. J. Ide captured this moment with a telescope protected by solar filters and the Canon EOS 300 D.

The red neighbour: Mars

Mars belongs without doubt to the most interesting astronomical objects. It is the only planet, which gives a view of its surface to our amateur telescopes. The most favourable time for Mars observations is when Mars is in opposition. That is, when the earth is exactly midway between Mars and sun. Then it is worthwhile to examine the Mars surface under the magnifying glass. Dark areas and the bright polar caps, which consist of frozen carbon dioxide, can be seen. The dark shades come from the different colours of the Mars soil, which consists of minerals containing iron. The thin Mars atmosphere and the high temperature differences between the day and night sides of the planet often lead to large sandstorms, which continually change the face of Mars. An amateur astronomer can already gain a small view of climatic conditions on Mars.

It is worth looking closely at the surface because many details can only be recognized after looking for a long time. The turbulent, terrestrial atmosphere is the enemy of the astronomer. With modern electronic picture recording procedures and the assistance of a computer, atmospheric disturbance can now be significantly reduced using amateur means.

Whilst observing Mars the distance between Mars and the earth plays a very large role. The distance between the earth and Mars varies very considerably. It varies between approx. 56 million and approx. 400 million Kms, depending upon the positions of the two planets. Therefore the diameter of Mars sometimes appears larger, sometimes smaller. On 28th August in 2003, the distance to the earth amounted to 56 million Kms. It therefore appeared particularly large. Observers of Mars had a looked forward to this event for a long time, because such an event only takes place every 1000 to 2000 years approximately.

Mars will show the observer many more details, as with the opposition in March 1997, which took place at the Mars aphelion. The planet was at the time about 100 millions km from the earth.

We used some technical terms which were not fully explained, during our little trip through the solar system. Therefore we have a collection of terms in our glossary.

Fig. 20: Mars, photographed with the Hubble Space Telescope/NASA

Jupiter and the dance of the moons

Now we come to the real “stars” amongst the planet, to Jupiter and Saturn. Once a year these two are in opposition and can be very easily observed a few weeks before or after opposition position.

Jupiter is a very bright, distinctive appearance, which is often erroneously interpreted by laymen as the morning or evening star. It takes nearly 12 years to complete its journey through the signs of the Zodiac. This means that each year opposition moves by one month. Despite its great distance from the earth, which in opposition amounts to over 600 million Kms, Jupiter reveals its planet segment shows us, which is 40 arc seconds in size. Jupiter is a gas planet and consists of hydrogen, helium, ammonia and further hydrogen compounds. It is covered in thick clouds. The atmosphere however has many characteristics. Like Jupiter it is surrounded by multi-coloured bands of cloud. The two main bands can readily be seen in the amateur telescope. After some minutes further bands of cloud can be seen. Perhaps also the famous “Great Red Spot” can be identified. This is a hurricane which has continued for at least 300 years and is twice as large in diameter as the earth.

Because Jupiter takes approximately 10 hours to rotate about its own axis, the mark is not always visible, but only if it is on the day side and is turned towards us. The fast rotation of the planet leads also to a flattening at the poles, which gives Jupiter a slight egg shape.

The quality of the visual image depends on the prevailing air turbulence. Amateurs call the air quality due to turbulence seeing. With good seeing it should be possible to see a whole number of impressive details in a four inch (102mm) telescope, such as the main cloud bands and the great red spot, for example.

As previously suggested in the heading, Jupiter has still more to offer than the cloud formations on its surface. Galileo Galilei (1564 to 1642) discovered four small spots of light, which change their position around Jupiter.

The four moons, also referred to as the Galilean moons, can also be identified in very small telescopes and they are recognisable even in binoculars. This requires however a very steady hand or the use of a stand. The remaining moons, at least 50 in number, unfortunately remain hidden from us. The visible moons are IO, Callisto, Ganymede and Europa. The position of the moons to Jupiter constantly change and offer us each evening a different view. Often one can observe how a moon disappears in front of or behind the planetary disk. Due to the cloud cover on Jupiter’s surface the moons often appear as small dark areas, which can be seen as black shadows on Jupiter’s surface, presupposing good seeing however. One can find out the position of the moons in yearbooks, such as “ Kosmos Himmelsjahr” (Cosmic Heavens Year). In these yearbooks all astronomical events for the current year are listed. They are consequently more than just an interesting reading for telescope owners.

Fig. 23: Saturn, photographed by the Vojager 2/NASA space probe

Fig. 24: Saturn, photographed with an entry-level telescope

The Lord of the Rings - Saturn

Saturn is the most impressive of the planets. Everyone has seen pictures of this ringed planet, but the live appearance of this planet is breath-taking. Observers experiencing this sight in the telescope cannot be removed from the telescope particularly during opposition, when Saturn shows an apparent planet of 20 arc seconds, then one can best observe the planet with its rings. In larger amateur telescopes, with good atmospheric conditions, separation of the rings into two can be seen. This is the Cassini division.

A further characteristic of the Saturn rings is the varying ring opening. Because of the slight inclination of the rings to the plane of the path of the earth, Saturn shows us the rings from all sides, in a cycle of approx. 30 years. In 1995 we were exactly at the level of the rings and Saturn seemed to be without rings. Afterwards the ring opening widened, so that the largest ring opening could be observed in the year 2002. During this time we saw the top side of the rings. Then for some years we could see the lower surface of the rings.

Like Jupiter, Saturn moons can be seen in the amateur telescope. The moon Titan is the most distinctive. In addition, the moons Rhea, Dione, Tethys, as well as Japetus can also be seen by amateurs. One knows the position of the moons from the yearbook “ Kosmos Himmelsjahr” (Cosmic Heavens Year). In this yearbook all astronomical events are listed for the current year.

In the depths of our solar system

After Saturn follow Uranus and Neptune, then at the very edge of our solar system the planet Pluto.

Uranus can only be made out very weakly with the means available to us. This gas giant can only be seen as a tiny, greenish pin prick, which can easily be confused with a star. It is therefore advisable to work with a star map or planetarium software.

The planet Neptune is also a huge gas giant, covered with cloud formations exactly like Saturn and Uranus with their vapour trails. Neptune can only be observed with telescopes starting from 6 " opening (152mm). It is interesting with this planet that, like Jupiter, it exhibits enormous atmospheric turbulence, which cannot be identified using amateur telescopes.

Pluto, the outermost planet in our solar system cannot be observed with the telescopes usually available or with the naked eye. This small heavenly body consisting of ice and rock is more a planetoid (small planet) than a true planet and only has a diameter of 2,250Kms. Pluto is an ice-cold world, it has an atmosphere and dances on its path around the sun completely on its own (see fig. 12 on page 15). Pluto was discovered as planet in 1930 and is still called a planet today - even if it is probably not.

Fig. 25: Uranus photo taken from the Voyageur 2 spacecraft/ NASA

Fig. 26: Neptune. The image originates from the NSSDC/ NASA database.

What else is happening?

After we have used the telescope to occupy ourselves with the sun and moon, with the planets and their characteristics, we might ask ourselves the question of what our solar system still has to offer.

Asteroids and small planets

In addition to the nine large planets there is still an immense number of small rock fragments in the solar system. Most of them are between the orbits of Mars and Jupiter. In the telescope these small objects are inconspicuous. Only 73 of the well-known small planets are accessible using small telescopes. In the yearbooks we often find only data for four of the largest of their kind: Ceres, Pallas, Vesta and Juno. Details of the surface are not recognizable with rocks less than 1000 Kms long. It is also not very easy to find small planets. If one nevertheless is able to seek out a small planet, one can observe its movement beautifully, relative to the fixed star sky. As a beginner one should not expose oneself to this test of patience yet, since this already presupposes a good knowledge of the heavens.

Fig 27: The Asteroid Ida, photo taken from the NASA space probe Galileo.


After the return of the Halley's comet in the year 1986 or the spectacular impact of the comet Shoemaker Levy 9 on Jupiter in July 1994 we were spoiled in 1996 and 1997 with particularly good comet appearances.

Hardly anyone could escape the media pageant surrounding the comets Hyakutake and Hale-Bopp.

Wonderfully we could identify the head and the beautiful tail of the two comets with the naked eye. Hale-Bopp, which acted as the century comet, in the binoculars showed the slightly curved dust tail and the bluish ionic tail, which result from solar radiation of animated gas particles. In the telescope one witnessed enormous jets, emissions of gas and dust from the comet’s nucleus, which supplied the material for the formation of the tail. For weeks the comet was brighter than the brightest stars in our sky. We cannot predict when we will again be able to witness such an event. Comets are unpredictable and are usually discovered coincidentally. No wonder that many amateurs hunt for comets themselves. Many comets are discovered by amateurs and then named after them. A challenge for the ambitious ones amongst us! Each year smaller comets, which are still visible in telescopes, are discovered. In addition there are also short period comets, which visit us once every couple of years. Their occurrence is usually inconspicuous, so that only a small, misty mark can be seen in the telescope. When searching for them the darkest skies are necessary.

Because of the unpredictability of the comets, one will find nothing in the yearbooks about the reSpotting scope positions of these objects. For current data one can fall back on technical periodicals or investigate the current data on the Internet.

Sources for comet data are for example the magazine “Sky and Telescope“, NASA Web pages or web pages of the International Astronomical Union Circular:

Furthermore there are many private homepages, which concern themselves with this topic. Use an internet search engine and enter terms such as “astronomy” or “comet observation”.

If these sources are not at your disposal, astronomical associations or observatories will gladly give you information. At the internet address you will probably also find an observatory in your neighbourhood. Follow the instructions about comets with caution. The position indicators can be out by several arc minutes or the predicted brightness can be completely out. Comets are just incalculable. That is the special attraction of the search. Finding these challenging objects are small successful experiences and also help progress.

An important note:
Small planets are inconspicuous objects and many comets are unfortunately also very faint, so that with poor visibility they can hardly be seen, if not at all. As a beginner you should not try this search yet. Finally there is much more still to see and discover.

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Fig 28: The Comet Hyakutake, taken by J. Newton.

Fig 29: The Comet Machholz, image taken by G. Strauch.

2.5.5 Deep Sky observation with the telescope

If one leafs through astronomical technical periodicals or thro u g h telescope dealers advertising brochures, then inevitably you will find the expression Deep Sky. As a lay person man you will probably immediately think of the spaceship Enterprise or similar science fiction, however this is not like that, at all!

Deep Sky is about far galaxies, but we do not have to leave our native planet. Astronomers describe all objects, which are beyond our planetary system as Deep Sky objects. As previously mentioned in the introduction, we are spoiled by the media and advertising with multi-coloured pictures of bright gas nebulae and galaxies. If we hope to see this colourful scene in the telescope we will be very disappointed.

The pictures involve long-exposure, photographic images, which cannot be seen with the eye, even with large telescopes. Nevertheless, one can see more with a telescope, than with the naked eye. The eye has a maximum pupil aperture of 8mm. With a telescope with just a 50mm opening the lightcollecting surface enables us to still see stars, which are seven times darker than the weakest stars, that could be to be seen only with the naked eye.

Fig 30: The open star cluster of the Pleides. Photographed by c. Kimball

Fig 31: The Pleiades seen here through a 125 Superplössl lens.

Let us now search for the double star Mizar and Alkor in the Great Bear.

Finding the seven stars of the Great Bear should not be too difficult for us. Which star however in the Great Bear is Mizar? A view of a star map will give us this information. The second star from the left in the handle is the double star Mizar/Alkor. Now let us try to lay on the pair of stars in the view finder of the telescope. With practice we will succeed and in the eyepiece we will see the beautiful double star Mizar and Alkor, which are popularly also called the “horse and rider”. Success! We have found our first deep sky object in the telescope.

Unfortunately is not so easy to find everything, as Mizar and Alkor, but with perseverance and practice we will come to know the sky better and better. No master of the heavens has to fall out of the sky. For very little money there are aids such as star maps or yearbooks.

We will now go on a tour of the universe. First let us try to identify the constellations by means of the bright stars and go in search of beautiful astronomical deep sky objects. Before we start our tour, a few further words on the visibility of the constellations. Not every constellation can be seen at any time. The earth, on its journey around the sun, always presents us with a new view of the sky. Every day the constellations rise about four minutes earlier. During the course of the year the sky is continually moving towards the west. Only after a complete year is the previous state produced again and the constellations are positioned where they are at present. An example: If a star around midnight today is located exactly in the south, then tomorrow it will be there four minutes earlier. This circumstance means that we do not see the same sky in the summer, as in the winter. When planning a night’s observations it is necessary to select the objects of the seasons accordingly. It does not make sense to look for the Orion nebula which is a winter object, in August. In chapter 2.7 “The most beautiful objects throughout the year” starting on page 29 a short guide, of what to see and when to see it, what is visible and worth observing and how to identify the correct object using star maps which can be rotated or so-called planetarium programs for computers.

Stars, star clusters, nebulae and galaxies

If one regards the nocturnal starlit sky sooner or later, faint, vague objects are noticeable to the observer. These are either gas nebulae, star clusters, the Milky Way or far off galaxies. The brighter objects are usually recorded on the star maps –we will now present some of these here.

Fig 32: The great Bear (also known as the Plough)

Fig 33: A planaterium software simulates the whole sky.

The Milky Way

The Milky Way, our homeland galaxy, is a spiral galaxy. It shows up as a resplendent band, which extends across the night sky. This comprises part of our star system. Our Milky Way looks from outside like a discus and has a diameter of 100,000 light-years and the thickness of 10,000 light-years (1 light-year is 9.46 trillion Kms). All stars move around the mass at the centre of the Milky Way. Our sun with its planets and moons, as well as hundreds of millions of other suns, moves on the journey around the galaxy nucleus. Far outside, on the edge of the galaxy is “the Milky Way”. A view of the Milky Way with binoculars or a telescope shows millions of stars, which are closely crowded together. Our homeland galaxy consists of over two hundred billion stars and from the outside looks like an enormous spiral. You might possibly see the spiral galaxy M 31 which is very similar. Our small planet earth, within our solar system, is located on the edge of the Milky Way, in one of the spiral arms. It is represented in Fig 35 by a green point •.The red arrow indicates our line of sight, thus we always see a small section of the next to last spiral arm. All stars, which we can see in the Milky Way, belong to our galaxy. Even through the strongest telescope it is not possible to see through this collection of tightly-packed stars. Nobody knows, how the universe looks behind the Milky Way.

Fig 35: Illustration of our Milky way

Fig 36: The spiral galaxy in Andromeda (M31), a photo by J. Ware.


Our galaxy (the Milky Way) is only one of innumerable galaxies, of which the universe consists. Some galaxies can be seen on a clear night from the earth, without optical aids. They look like faint spots of light in the sky, a conglomeration of millions of stars. The outlines of the galaxies can only be made visible by using long-exposure photography. Galaxies predominantly arrange themselves into groups. Our group of galaxies, also known as “local group”, consists of approx. 30 galaxies, which together form a radius of 2.5 million light-years. Not all galaxies have developed as spirals. Some are asymmetrical, others have are approximately circular or have an elliptical shape. The galaxies closest to us are constructed as somewhat asymmetrical mini- galaxies, known as the large and small Magellanic Cloud. These galaxies can be seen only from the southern hemisphere.

A well-known galaxy is in the constellation Andromeda. This can be seen with the naked eye. The galaxy is about 2.2. Million light-years away and looks like a misty speck. It consists however of a large spiral galaxy, similar to ours.

Fig 37: The Sombreo – Galaxy is also of the spiral-type and we can only view it from the side. This image belongs to J.Hoot.

Star clusters

There are two different kinds of star clusters. “Open star clusters” which consist of bright, young stars which were formed from galactic nebulae (bright hydrogen and oxygen gases). The other form of star clusters are “the globular star clusters”. These are substantially larger and further away than the open star clusters. Both kinds can be observed using a small beginners telescope.

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Fig 38: The Globular star clusters M13 taken by J. Newton

2.6 Practical observation tips and tricks

2.6.1 Preparations for the first night


An observation night needs to be well prepared. You should know your equipment and make yourself familiar with its operation in the daylight. Carry out a dry-run in setting up and also operating and testing any electrical accessories, such as a tracking motor or binoculars for finding the Pole star. When you come to set up the equipment at night you will save time and can concentrate on observation. It is also sensible to adjust the eyepiece telescope in daylight as it requires practice to do so at night. A far distant tower is a useful aid for setting up, also the choice of the observation place must be well thought out.

If you live in a large city you are forced to drive out into the countryside with your telescope. This is the only way to escape light flooding from street lamps and hoardings. A dark sky shows far more than the lightcontaminated skies of a large city. People who live in the country have an advantage here. If we drive out into the country with the telescope, then we should first inspect the location in the daylight. Finally, you do not want to sink into a bog or be plagued by mosquitoes. Damp places should be avoided, as with rapidly sinking night temperatures the optics soon become misted up. A small hill is ideal and also offers an extensive view of the horizon. As far as cold nights are concerned you should always have warm clothing to hand. Once you are frozen through, then there is no more pleasure to be had. Athermos flask of or coffee or tea will help you to keep warm. What else should you also load into the car or into your bicycle panniers? Naturally the telescope and its accessories, a warm coat, hot beverages, a compass, a flashlight (covered with red cellophane) are important. Binoculars are also a welcome observation aid. In addition you should think of somewhere to sit. Take a folding chair or stool with you. A comfortable camping table will also prove very useful for laying out the accessories, for the star map material needs to be close by. You should examine it in the daylight and pre-select the celestial objects for the observation programme. This will make the subsequent search of the night sky easier. In the course of the time, you will notice that you will find your way better about the sky and will be able to find the more difficult celestial objects. To start with however, you should begin with objects which are easy to find and we will refer to these later.

After arrival at the observation site, setting up the equipment and orientation to North can be commenced, as described in the instructions. After approximately half an hour the eyes will become accustomed to the darkness and more stars can be seen than when we arrived.

It does not make sense to cancel out this adaptation of the eyes to the night by briefly looking into bright sources of light again. Furthermore, vehicle headlights or even the light of the flashlight are enough. The first should not be a problem, because we would not set up the telescope directly in a highway lay-by. In order to avoid the light of the flashlight, cover it with red foil. The red light only slightly disturbs night vision. Flashlights, which can be switched to give red light are excellent.

The telescope also requires several minutes, in order to adapt to the ambient temperature. Only then will the optics brings be fully operative. The circulation of air in the telescope tube during cooling makes the image waiver considerably, so after waiting for a while it is finally time to look into our telescope for the first time. It is best to use the low magnification eyepiece at first (long focal length), in order to have a larger field of view with the lower magnification. The required object will then be easier to find. Our first object could be, for example, the moon, or a planet, depending on what the sky has to offer us. If neither can be seen, then perhaps we can choose a double star or a star cluster, which we were able to find on the star map.

It does not matter which of these we select. The sky will not run away from us and there are many more nights of observation waiting for us.

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Fig 39: A red LED lamp with clip

2.6.2 Tips for the best observation conditions

The observation conditions play an important role during the observation with a telescope of the sun, moon, planet and stars. In addition the site of the observations is also significant, for example, the visibility conditions, as well as the condition of the telescope and the condition of the observer. Only when all observation factors are in order will it be possible for us to fully utilise all the optical abilities of our telescope. If we work under poor observation conditions, this can easily lead to disappointments and will give the impression that we have acquired a poor quality telescope. The following information and tips will help you decide whether the construction of the telescope is worthwhile or not.

The observation site

The observation site should be as dark as possible and be faraway from terrestrial sources of light (street lamps, headlights etc.). There should be all round visibility in all directions. Protection from the wind should be provided, so that the telescope will not “tremble”. This is possible by using a suitable windbreak device, for example like those used when camping by the lake. We will rarely find an ideal observation place, without making a few local changes. In most cases we live in enclosed surroundings and our observation sites are the garden, the terrace or the balcony. In order to protect the site against the influences of light from terrestrial sources a sun umbrella can be used. A further possibility consists of placing a black cloth over the head and the eyepiece of the telescope, like photographers used to do in the early days of photography, so that they could see the picture in the camera clearly. Finally our observation place should be on firm ground, so that our telescope remains stable. Observation from the heated living room through a closed or open window is impossible. The window glass causes too much disturbance. In addition, the temperature difference between living rooms and garden would lead to streaks of moisture and thus to considerable disturbance, making it impossible to focus the object.

Viewing conditions

The local weather and the condition of the earth’s atmosphere considerably affect the quality of the images in our telescope. When making astronomical observations we always look through the layer of air which surrounds the earth. Depending on the thickness of the surrounding atmosphere for instance it corresponds to us like the peel of an apple. If strong air turbulence is present and warm and cold air masses are mixed together, it is not possible to take meaningful observations with high magnification. We see this in the fact that the stars sparkle and twinkle in a range of colours. Especially during winter time turbulent air layers are immediately apparent. A further feature is thin ice clouds at high altitudes, which similarly disturb our observations. These lead to coloured rings around the sun or moon. The bright nights of the summer are also only partially suitable for the observation of faint objects. If the light of the moon illuminates the sky’s background, we cannot expect to obtain the best performance from our telescope. The best conditions in Central Europe are usually in the autumn and in spring if the sky is clear, the air layers calm and not clouded by vapour. The light from the stars appears calm with the naked eye and the sky background looks like black velvet.

Condition of the telescope

To allow the telescope to adapt to the outside temperature it should be set up and aligned in the open, about 30 minutes before beginning observation. During observation the lens or the mirrors can be affected by humidity. A hand warmer, available from specialist angling shops, can be used to remove dew from the lenses. A hair dryer can also do this well (if necessary a12V-model operated from a car cigarette lighter). Under no circumstances should a cloth be wiped over the optics, because existing dust grains can result in scratches. One trick to stop misting up, is to use a protective lens cap to prevent dew. This which is clipped or screwed onto the front of the telescope tube. If not already provided, these can be purchased separately as accessories.

Fig 40: A lens telescope with a screwon dew protection cap

Condition of the observer

Astronomical observing is not a high performance sport. It serves primarily to relax and provide new experiences. Make sure that you are fully rested. Observations in an overtired condition are not productive and cause stress to both mind and body.

A further word about our valuable organ, the eye. The full efficiency of the eye is only produced when night observations take place after approximately half an hour in the dark.

The diameter of the pupil of the eye, in young humans, can be up to 8 mm; experience has shown that the value decreases with age. Although the pupils adapt within seconds to the lighting conditions, the eye then needs up to 30 minutes, in order to fully adapt to the light, by means of the body’s own chemical substances. With bright light this adaptation is lost within seconds and must again be developed. Therefore interference from light is to be avoided whilst observing, if possible.

A bright source of light, a headlight or a bright flashlight immediately destroy the eyes dark adaptation (night vision), so that we must wait again for half an hour, until we are best adapted to the darkness. Experience this just once and you will be amazed!

General points for observation:

1. Draw up a short observation list together. In this way you will not be stressed out in front of the sparkling heavens. Consider the reSpotting scope observation conditions. The full moon will spoil the pleasure of deep sky observations, even if you have a suitable observation place far away from terrestrial sources of light. In this case take brighter objects into the sights.

2. Do not choose too many objects. More is less! Look at the maps for finding your favourite objects well beforehand. In this way you will also quickly find them in the sky.

3. Use your binoculars to look at the sky and orientate yourselves. In the telescope, even with low magnification and reduced field of view, it is often not really easy. Practice.

4. Observe the objects you have found a little longer. Practice obtaining a relaxed view. Avoid the rigid view, let your eye float over the eyepiece. The longer an object is observed through the eyepiece, the more details open up to the eye. Often the optical light images are so weak that one learns and uses the full efficiency of the telescope with the possibilities it offers to see and perceive. The eye can also think. You will see more with increasing observation experience than at the beginning of your astronomical career. Even Galilei (1564 to 1642) and Newton (1643 to 1727) had to experience carrying out observations of the sky with small telescopes. Many followed them. You must also strive to follow them!

5. Keep an observation book, in which you record your impressions, either in writing or you can draw the objects on paper.

6. It does not always have to be a photo. You can draw the objects you have seen. Drawing is very popular among deep sky fans and is very suitable for the beginner, since astrophotography is often very difficult for the lay person. Different pencils and erasure techniques open up a whole range of objects for you. Compare your drawings with the photographs of the professionals and you will be surprised.

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2.7 The most beautiful objects throughout the year



M42, the famous Orion nebula, is below the three belt stars of this distinctive constellation. This is a very bright emission nebula and a worthwhile object for every telescope!



Fig. 41: The seven daughters of Atlas, the Pleiades fleeing from Orion because he is so gigantic

Fig. 43: The image of the Whirlpool Galaxy, M51 by J Ware

Fig. 45: The globular star cluster M13 taken by J.Newton

Fig. 46: Ring nebula M57, taken by M. Moilanen and A.Oksanen

Fig 47: The spiral galaxy M31 (in Andromeda), a photo by J.Ware

The Hyades between “the horns” of Taurus and the Pleiades are large socalled open star clusters. In particular the Pleiades are remarkable even with the naked eye. They are northwest from Orion and can be observed with low magnification.



M 51, the so-called “Whirlpool galaxy”, is somewhat below the left hand star of the handle bar of the Great Bear. This is a double galaxy, which can be clearly seen in a dark sky size with a medium telescope. It is better to drive out to rural areas for this observation. The light contamination of the city makes it very difficulty to observe this object.



Fig 42: Berenice, the wife of the Pharaoh Ptolemy III, because of love, offered her magnificent head of hair to Aphrodite for the healthy return of her husband from the war.

“The Manger”, M 44, is a large open star cluster in the constellation of cancer. The large planets Jupiter and Saturn often travel past in close proximity, since they lie close to the ecliptic; a very beautiful sight!



M 13 in Hercules is the brightest globular star cluster in the northern sky. With high magnification individual stars can be seen, even with small telescopes. M 57 is the famous “ring nebula” in the Lyre, the prototype of a planetary nebula. It is just below Vega, between the two lower edge stars. Slightly higher, east ofVega, is Epsilon Lyrae, a double, double star system! Albireo, a very pretty double star with a clear orange-blue colour contrast which finally forms the head star of the swan. A worthwhile object for every telescope!



Fig 42: Hercules fights with Draco (the dargon) in the garden of the Hesperides



M 31, the Andromeda nebula with its approx distance of 2.2 million lightyears is the closest and largest visible galaxy to us after the Magellanic Clouds of the southern sky. It is well over 3°wide in the sky (about the width of the thumb on an outstretched arm) and can be seen with the naked eye if the conditions are good. We know today that it is not a nebula, but a galaxy.



Fig 48: The winged horse Pegasus rising from Medusa, after Perseus had defeated her and then pulled the chariot of Zeus.

Somewhat more challenging is M33 in the constellation Triangulum. This galaxy repays patience at the telescope with many fine details. h & ?(Chi) Persei is finally a large double star cluster south of Cassiopeia. In the case of low magnification in the telescope or also in the binoculars it offers a splendid sight in either optics!

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