INSTRUMENTS

ASTRAL TELESCOPE

page 11

OTHER STARS IN THE SOLAR SYSTEM

STELLAR MASSES
If it is easy to find star couples in the sky, that is double stars, it is easy also to find star groups that have more than two components. In fact this is even more common. These are known as open clusters or galaxies and are beautiful to observe with a small instrument. A certain number of these are visible to the naked eye as a group of stars, but the majority look like a flock of light hot easy to identify. Their nature as stellar masses is clear however when seen through a telescope. Refer to the maps at the back of this manual in order to identify the objects described. The masses, just like the nebulae and the galaxies, have been catalogued in various ways, but the most common sign is the letter "M" followed by a number, and this refers to the catalogue compiled by the astronomer Charles Messier in the 18th century.
In the winter sky, the mass which is easiest to see is that of Pleiades, in the constellation of Taurus. With the naked eye, it is possible to courir up to 7 stars, whereas with a 114mm, it would be possible to observe more than 50 within the field of the ocular. In the spring sky, it is easy to find, and to "lose" in a cloud of stars, the mass of Praesepe (M44) which is found in the zodiacal constellation of Cancer.
The double mass of h and Chi Perseus is magnificent in the autumn sky. It is perceptible to the naked eye between the constellations of Perseus and Cassiopeia. With a telescope it is possible to see hundreds of stars at a glance.
Among the stellar masses special mention must be made of the category of globular masses.
These are enormous and distant objects, composed of hundreds of thousands of stars, collected together in a reduced space. The telescope can show us many of these, among which we mention M3 in the constellation of Canes Venatici and MI3 in Hercules, which is the most extensive and brightest of the celestial Northern Hemisphere. We recommend observation also of M22, in Sagittarius and of M5 in Serpents, both of which are beautiful and well extended. Observing these objects with a telescope at a medium degree of magnification (80 - 100x), they will have the appearance of a spot of light, rounded and milky. On some particularly clear, dark evenings it will be possible to individuate stars in the regions surrounding the brightest patches of light. If you carry out your observation with an instrument of wider aperture, these objects will be revealed in their true nature as stars.

NEBULAE AND GALAXIES
Nebulae are enormous agglomerations of interstellar gas, rendered luminous by ultraviolet rays emitted by very hot stars which are to found at the center of the nebulae. Dark Nebulae also exist, visible only at the base of illuminated gas. The nebulae come in various forms and shapes, in general irregular, even if in the case of planetary nebulae the form is rounded like a ring of smoke. An example of planetary nebulae is visible between the two stars beta and gamma in the Lyra constellation in the suremer sky. We are talking here of M57, known also as the Planetary Ring Nebula. It is small and therefore needs to be observed with magnification of at least 50X. The most famous and most beautiful of ail the nebulae visible in the northern hemisphere during the winter season is, without a doubt, M42, known also as the Great Nebula of Orion. This is a splendid object, in the form of an open fan, with, at its center, the quadruple star "theta" of Orion the four components of which (the trapezium) are relatively easily visible at a degree of magnification (40 - 50X) In the summer sky, if we aim out telescope towards the Milky Way which crosses the constellation of Sagittarius, we will be struck by the great variety and beauty of the nebulae contained within it: Ml7, also called Omega, has a shape which brings to mind that letter of the Greek alphabet; M8 and M20, are also called Lagoon and Trifid respectively, the first for its rounded shape which brings to mind the shape of a bay and the other because of the dark nebula which crosses it and divides it into three parts.The Galaxies are the most distant objects visible with the telescope. Their distance is measured in millions of light years.
The light, which travels at a fantastic speed of 300,000 km a second takes millions of years to cover the distance separating them. For this reason, we see these objects as they were millions of light years ago and not as they are now.
Galaxies are immense islands in the universe, made up of various millions of stars and an enormous quantity of gases and dust. We too are at the center of a galaxy, in company with millions of other stars. The galaxies are separated by enormous distances, and they move away from each other.
The form of the galaxies can be spiral with a variable number of arms, at varying distance from each other.
The brightest of the visible galaxies is, without a doubt, the M31, in the constellation of Andromeda. This is one of our neighboring galaxies, about two million light years away, visible as an oval, brighter at its center, which shines like a star of magnitude 4, and therefore visible to the unaided eye on clearest nights.
To the south of Andromeda, the galaxy M33 is to be round, in the constellation of the Triangulum. This galaxy is "sparse" and it is difficult to describe. In the constellation of Canes Venatici, beneath Ursa Major, lies the beautiful M 51 spiral galaxy, called Vortex because it is seen from the front, If you look a little at random in the zone of the sky lying between Leo and the Coma Berenices (Berenice's Hair), you will certainly find curious flocks of light that are none other than galaxy clusters. These objects are weak and distant from us and need to be observed at a medium level of magnification.
They are not usually visible through the finder, and so you will need to look tentatively through the telescope in order to find them, having first looked at the sky with the unaided eye and then looked at the map of that part of the sky on the Celestial Atlas.