This training course is reserved to the students of the Master de l'Observatoire de Paris and takes place at the Observatoire de Haute-Provence. This training course may also be proposed to students of schools of engineering and of universities under specific conditions. French speaking is recommended.


As a part of the teaching program of Master Fundamental Astronomy, Celestial mechanics and Geodesy, the Institut de Mécanique Céleste organizes a one week stay at the Haute-Provence in March. The aim of this training course entitled Introduction to CCD astrometry is to allow students who followed courses of astronomy and theoretical astrometry to supplement their formation by an introduction to the techniques and methods of modern astrometrical observation.

This document gives general information on the observations which are carried out in the Haute-Provence Observatory and the used instruments. This training course was prepared and is supervised by J.-E.Arlot, F. Colas and D. Katz


For any further information please contact :

    by email : Institut de Mécanique Céleste
Stages d'initiation à l'observation
Jean-Eudes Arlot
77 avenue Denfert-Rochereau
F-75014 Paris
  by email :

  by telephone : J.E. Arlot  : +33(0)1 40 51 22 67
F. Colas : +33(0)1 40 51 22 65
D. Katz : +33(0)1 40 51 22 49
(from 9 a.m. to 12 a.m. and from 14 p.m. to 17 p.m. the working days)
  NOTA: Part of this document is founded on the information given by the Guide Pratique de l´OHP


The Observatory of Haute-Provence (OHP) is situated at 2 km in the north of the village of Saint Michel-l'Observatoire and at 12 km of Forcalquier (the Alps of Haute-Provence), at an altitude of 650 meters on a oak wooded plateau. Its construction, decided in November 1936 by a committee chaired by the physicist J Perrin, start in 1937. The 0,80m telescope was the first instrument installed on the site, and it is in 1958 that the 1,93m telescope operates, it was the biggest telescope on the national territory. The development of the main European observatories (the ESO in Chile) or international (the CFH in Hawaii), in sites of high altitude and good quality of transparency and stability of the atmosphere transformed the role of the national observatories such as the OHP. The OHP gives the access to several instruments of excellent quality supported by a consequent infrastructure giving it a complement role of the distant main observatories. It is a well adapted site to carry out, in particular, long-term works such as astrometry. The images are of average quality but the number of usable nights is rather high.

The OHP lodges a scientific group composed of J.P. Sivan (head of the OHP), A. Labeyrie, H. Le Coroller, C. Chevalier, D. Gillet, S. Ilovaisky, Ph. Véron and M.-P. Véron-Cetty. It is composed of administrative services (administration, missions and library) and of engineering departments (optics, mechanics, electronics, detectors, maintenance of the telescopes). The whole of these services gathers approximately 60 people.

L´OHP (see observatory plan) is a mission observatory, it thus provides to the astronomers on mission of observation several essential services. Lodging is carried out on the site in the premises of the Maison Jean Perrin where are available double or single rooms, and common premises for the meals. A dome assistant is affected to each telescope used by the astronomers on mission; his role is in particular to take care of the handling of the instrument (pointing and follow-up of the objects) and of the implementation of the detector if it is about the OHP instrumentation. He has authority to control the compatibility of the use of the instrument with the safety requirements.


The training course takes place from Monday March 26th evening until Saturday March 31st morning.

The trainees are lodged on the spot and the meetings of observation proceed each night from sunset time... to the daybreak if the weather allows it. We have 3 different telescopes equipped with cooled CCD detectors. Each night the trainees are divided by groups of 4 per telescope and are brought to take part in various kind of image acquisition. The afternoon, conferences will be possibly given, the data processing and the observations of the following night are prepared from the field charts and the necessary ephemerides.

The observers have additional laboratories adjoined to the domes and from which the acquisition of the data is carried out. The handling of the receivers and the telescopes is under the responsibility of a dome assistant. However the telescopes are at the outside temperature and it is useful to have hot cloths even in August... In addition, any external light is banished from the observatory and it is advisable to have a flashlight to be able to circulate from one building to another during the night (access to the domes, the library, the restaurant and the rooms).


Access to OHP

The OHP is located at 2 km in the north of the village of Saint-Michel-L' Observatoire in the Alps of Haute-Provence (04). It is situated 20 km of Manosque, 30 km of Apt (Vaucluse), 80 km of Avignon and 100 km of Marseilles (see map 1 - region and map 2 - OHP surroundings). Map 1 is extracted from the map of Michelin 919 "France-Sud" in 1/1000 000 and map 2 is extracted from IGN map in 1/100 000.

Access by road :

 From the valley of the Rhone: nationale 7 or motorway A7 then D22 near Avignon (Apt direction), then N100. 30 km after Apt, take the direction Saint-Michel-l'Observatory on the left.

 From Marseille:

 Take the direction of Aix-en-Provence then the N96 or the motorway A51 towards Sisteron. In Manosque take the direction of Apt by the D907. At 10 km of Manosque, take the D105 on the right towards Saint-Michael l'Observatoire.

 Accees by train :

 The OHP is close to the stations of Avignon (80 km), Aix-en-Provence TGV (90 km) and Manosque (20 km). We recommend for the trainees coming from Paris, to take the TGV to Marseilles or to Aix-en-Provence-TGV, then the train (from Marseille) or the bus (from Aix-TGV) until Manosque. We will wait for you at the station of Manosque to lead you to the observatory.

Timetables are available on the SNCF web site or on the DB web site.


The OHP is equipped with a UNIX and PC workstations network that the astronomers on mission can use to communicate and work. The trainees have an access to this network and to Internet.

The principal useful phone numbers are :

Standard :   04 92 70 64 00 
Dome telescope T80 :   04 92 70 64 19 
Dome telescope T120 :   04 92 70 64 20 
Dome telescope T152 :   04 92 70 64 69 
Library :   04 92 70 64 86 
Jean Perrin House :   04 92 70 64 47 
FAX :   04 92 76 62 95 


Three telescopes are used : the telescope of 80 cm, the one of 152 cm et and the one of 120 cm. These three telescopes are equipped with a CCD (Coupled Charge Device) detector and with an associated computer. This type of detector revealed to be a detector of a great interest for astrometry because of its great sensitivity and its geometrical stability. It allows acquiring images in numerical form that we can thus handle with a computer (PC) thanks to specialized software. For these treatments we use either a software application called Astrol, or the Midas software under Unix of which a detailed documentation is available.

You can find the CCD characteristics used at the OHP on the Haute-Provence Observatory website (and information on the 120 cm telescope camera and the 80cm one).


Several types of observations basically on the solar system objects are carried out. The data acquisition (identification of the object, handling of the telescope, parameter setting of the detector, acquisition) and their pre-treatment are also carried out. As far as possible, similar observations are carried out on the two telescopes (T80 and T120) to lead to comparable astrometrical measurements. Some observations are only possible on a fixed date : it concerns observations of occultations phenomena. Other observations and in particular the observations of astrometrical calibration can be carried out with less constraints.

Various observations :

The practice of the observation requires the knowledge of some fundamental operations of the observational astronomy : to know to point the telescope, to know to identify a field and to find the sought object even if its magnitude is low. First of all, it is necessary to proceed to this type of handling by observing characteristic fields (stellar clusters, galaxies...) and by seeking certain objects of the solar system (Pluto, comets, asteroids) visible at that time.

The solar system small bodies : asteroids and natural satellites of planets

The small bodies of the solar system are many objects which interest much the astronomers because of their variety, their dynamic and physical characteristics and which can give essential information concerning the origin and the evolution of the solar system. During the training course, astrometrical observations of these bodies will be carried out by using simple software of astrometrical reduction.

Occultations Phenomena :

The small bodies of the solar system, often visible high speed, present particular phenomena giving access to very great astrometrical precisions: the occultations phenomena : stellar and mutual occultations. These two types of observation will be practiced during the training course as such phenomena are observable.

In the case of stellar occultations, it will be a question of seeking to observe a fast variation of luminous flow when a small body passes in front of a star. In case of success these observations give access to astrometrical measurements of a relative precision of about a 0.001 second of degree and to the shape of these objects.

Cometary observations :

In 1997 we could observe a very active comet, the Hale-Bopp comet. If the observation of a very brilliant comet is rare, many comets are however, observable each year and research and observation of the movement of these comets compared to the star field will be carried out.

Calibration on double stars and star cluster :

To carry out useful astrometrical observations, it is necessary to know the geometry of the CCD target. For that it is possible to carry out the acquisition of known stellar fields images, well measured by other astrometrical instruments. One can use for that the double star or globular clusters observation. The difficulty often lies in the fact of choosing objects of small field calibration (core of globular cluster) near the field of the objects of which we study astrometry. We proceed to this type of observation of calibration by observing certain double stars and the clusters M13, M67, M53. These observations should enable us to determine target constants useful for the astrometrical reduction of any other object.


Spectroscopic measurements :

  The 152 cm telescope allows doing spectroscopic measurements with a spectrograph "Aurélie" equipped with a new CCD. In addition to traditional measurements, we can practise the radial speed measurements, for instance, to identify stars of a cluster. Tests on the solar system objects will be carried out. Thus, we will see that the spectroscopy can give information not only on the composition of the bodies but also on their position and their movement.


Several works or articles allow obtaining general information on the solar system objects, astrometry, or the CCD techniques of observation and analysis :

Colas, F., Arlot, J.-E.: 1991, Comparison of observations of the Martian  satellites made in 1988 with ephemerides, Astron. Astrophys. 252, 402

Colas, F.: 1991, Nouvelles observations CCD astrométriques pour  l´étude dynamique des satellites des planètes:  application au mouvement du satellite Thébé de Jupiter,  Thèse de l´Observatoire de Paris.

Colas, F., Buil, Ch.: 1992, First Earth based of Neptune's satellite Proteus,   Astron. Astrophys. 262, L13

Buil, Ch.: 1990, CCD Astronomy, William-Bell Inc.

Chiu, H.Y, Warasila, R.L., Remo, J.L.:  Stellar astronomy,Vol. 1,    Gordon and Breach

Encrenaz, Th., Bibring, J.P.: 1989, Le système solaire,   Inter Editions, Edition du CNRS.

Gordon Walker: 1987, Astronomical Observations, Cambridge University Press.

Green, R.M.: Spherical astronomy, Cambridge Univ. Press

Kovalevsky, J.: Astrométrie moderne, Lectures notes in physics,   Springer Verlag

Léna, P.: 1986, Méthodes physiques de l´observation,   Inter Editions, Edition du CNRS.

Levallois, J.-J.: Géodésie générale   Tome 1, Eyrolles.

Van de Kamp, P.: Principle of Astrometry, Freeman and Co., San Francisco


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