General knowledges about asteroids      

On 1th January 1801 Giuseppe Piazzi discovered from the Observatory of Palermo the first asteroid 1 Ceres, a  1000 Kilometres diametre rock body on a  2,77 UA almost circular orbit  from the Sun.

From that  many other asteroids were discovered and today we know 260.000 asteroids. Every asteroid is known and identified by a provisory abbreviation. After few year this abbreviation is replaced by a number with discovering name. The bodies with an orbit established  with a good precision  are more of  90.000.

Besides the Main Belt, there is an under population of asteroids, whose trajectories are in the Mars orbit. These bodies are divided in 3 groups: Athens , Apollo and Amor (on the strength of covered trajectories). Athens and Apollo have part of their orbit in earthly orbit, but in orbital period, respectively, greater or smaller in a year. Amor have orbits outside from earth orbit, but with distance  to shorter perihelion 1,3 UA. On 25 october 2004 were 246 Athens well-known, 1461 Apollo and 1330 Amor, 3037 objects in all.

The first asteroids with orbits in earthly orbit are discovered recently. Dates are 11th february 2003 for CP20, 10th may 2004 for JG6. This type of asteroids were preceded like evolution of Athens , Apollo, Amor and are well-known like Inner Earth Object (IEO, objects inner the earth). Commonly all the objects (asteroids or comets) that can push themselves towards earthly planet are called NEO (Near-Earth Objects). If you consider only asteroids, you can speak about NEA (Near-Earth Asteroids). The NEO  that can reach shorter distances to 0,5 UA from Earth and have a diametre more large of 150 metres are called PHO (Potentially Hazardous Objects), because are at the risk of collision with our planet. PHO well-known are 599.

Neo survey

Lover Equipments

Even non- professional astronomers  contributed to identify new asteroids and  survey too. Here are someinformations  about how to become an astronomer.

First of all  some information about the  telescope. It has to have a minimum diametre of  20 millimetres , although a diameter of  25-30  millimetres are more suitable. The Newton reflector has an excellent price for their quality. The equatorial assembly must be steady for pose that aren’t driven for almost 60 bits and it must be in able to hold CCD cameras and driving telescope ( 70- 90 millimetres diametre). Assembly must be computerized and  able to point optical pipe in the best position with care about some minutes.

Endly the CCD camera which  must be  chilled type in order  to decrease the noise. The sensor has to have highest possible efficiency of quantity to supply  a good link signal sound with pose about some bits dozen. The magnitude to reach is almost the +18,5/+19 with 60 bits poses in ideal sky conditions.  The electrical device CCD is excellent (under this point of view) on the sensor surface. Microlens perform their function like bus, routing the radiation towards the middle  zone of pixel (the zone most sensitive). In this way a CCD with electric lighting head-on ( the CCD type most widespread) can reach a top efficency about 0,8 ( that is detected the 80% about incident radiation in  a defined wavelength) that is comparable with CCD wavelength (that are back illuminate and more fragile and expensive).

Luckily for astrometry you musn’t use optical filter and you have to avoid a parasitic percolation of radiation (that is always not too much). It’s advisable to have square pixel with not little dimension (almost 9-10  centimetres for side, it’s better to have 15-20  centimetres)iin order to have a good sensibility in a low level of lighting. CCD camera must be manageable by computer with an efficient control of temperature, in order  to preserve the same value in time.

MPC code

When you have right equipments, you can begin the observations.You need to became observers at Planet Center (MPC), your international centre about data-gathering of astrometric observations, in roder to make better the work. To obtain a code for the observatory  you have to prove that the accuracy of the  measure is equivalent or lower to bow bits. For this reason you have to  observe a numerated asteroid (so about orbit well-known), with order number larger than 3000 (magnitude between 16+ and 17+) and send the measure to MPC. If the rejects are lower to bow minute will be assign a code  that identify the observatory. The wait time is short ( in my case it  was of  24 hours). Concerning about  sending of the subsequent observations,in according to an appropriate codification, you must always use the assigned code. If you change the area of observation you must repeat the praxis. For informations about technical details you can read the “manual to astrometry” that you can download from MPC website. This is  an helpful newest manual. After this preliminary step  you can enjoy yourself in the exciting world of  astrometric observations of  asteroids.

In the research of new asteroids a non-professional observatory must compete with professional survey, especially with the "LINEAR" program.  NEO survey  have a grate advantage and from their utility the non-professional discoveries have had a decrease.  The real problem is if it could be a trick (that is possible)

Survey are specialized in NEO research, so asteroids that have a high motion for almost some bits in a minute. The spotting of objects with lower motion is difficult ( for less than 10 bits in a minute). These" slow asteroids" can avoid the survey, but not to non-professional  station if you have the watchfulness to observe them for a little while. The remaining problem consist in identifying on the  celestial sphere the regions in which asteroids have a slow motion.  You need to guess the orbit of the  asteroid that you want in order to identify  these points.

 We suppose to have an asteroid that it hurries up on the ecliptic of an external circular orbit to the orbit of earth, so a body that belong to Main Belt. The apparent trajectory on the celestial sphere is on a quality level similar to the one of  Mars: periods rotate themselves in backward motion (during opposition), from east to west to direct motion periods from west to east. During the reverse of motion from direct backward or vice versa, asteroid motion is in a condition of nothingness (station points). You must control these points with your own telescope. There are two station points, that are proportionate with the opposition point of the asteroid to the Sun

Photometrical study

Filmato 

RADAR

A part of the research quite ignored by astronomers is the photometrical observation of asteroids. It consists in setting the rotation period about flow of light curve (similar to the process for variable stars). Only  for a short fraction of known asteroids, about 2000,  the rotation period is known (only 2% of numerated asteroids!!), so in this range there is space for all.

The simplest type of observation is the differential photometry, without the use of expensive photometrical standard filters. This method consists in setting the difference of magnitude  between the asteroid and a control group star ( that isn’t variable), of magnitude and with similar color placed in the same image. In these conditions you don't need to correct the atmospheric percolation and the variations of light curve allow to establish easily the period. To control, check with the same comparison, that another  star of sphere don’t stand waver of magnitude. Many asteroids have short periods, so is possible set the exactly measure with observations made in one or two nights.

There are  two good reasons for the photometrical observation of asteroids: the observations on the light curve  can be used for set the shape of body and the orientation of rotation axis of asteroid. These informations are essential to plan the future space missions.

The simple determination  about a  big number of periods is interesting. Until today few things with period under 2,25 hours are found (under this time-limit a thing composed by a aggregation of  bodies pieces). This means that most of asteroids are made by the aggregation of independent bodies and not by blocks. A greater statistics on periods allows us to determine the dimension under it you get the passage of asteroid composed to monolithic one.