Muiños, J.L., Belizón, F., Vallejo, M.
Real Instituto y Observatorio de la Armada,
Plaza de las Marinas s/n,
11110 San Fernando,

Mallamaci, C., Pérez, J.A.
Observatorio Astronómico Félix Aguilar,
Avda. Benavídez 8157 oeste,
5407 Marquesado,
San Juan,


The meridian circle of the Real Instituto y Observatorio de la Armada en San Fernando (ROA) was built in 1948 by Grubb-Parsons. In 1987 the observations were stopped and began a process of complete automation of the observations in a similar way as it twin telescope the Carlsberg Automatic Meridian Circle (CAMC). In 1996 after a period of test observations in San Fernando was moved to Argentina, to the Carlos U. Cesco (CUC) observatory of the Observatorio Astronómico Félix Aguilar (OAFA) of San Juan University where is operate jointly by the ROA and the OAFA. The CUC is placed in the west of Argentina near the Andes at 31º South, 69º West and 2330 m over the sea level. Since 1996 August to 1999 November the observations were carried out with an scan slits micrometer. On 1999 December an Spectrasource CCD camera of 1552x1024 pixels of 9 ( , borrowed by the Copenhague University Obsevatory, was installed in the instrument. The CCD camera observes in drift scan mode. Since then a survey of the South sky from 0º to -60º is been observed. Maximun priority is given to the zone -3º to -9º the same zone observed in San Fernando for the Astrophotographic Catalogue in order to computes proper motions using new measures of the AC plates.


The Círculo Meridiano Automático de San Fernando (CMASF) is a meridian telescope with 2664 mm of focal length. The object glass is an achromatic doublet with an useful aperture of 176 mm built in 1997 by Ealing. In 1991 the original declination glass circle was changed for a new one built by Heidenhain, the circle has 724 mm of diameter and is engraved every 5 minutes. Since 1999 December observe with an CCD camera working in drift scan mode (Gehrels, 1991).

The observations are carried out in a completely automatic mode. The automation is controlled by a PC, the telescope controller computer (TCC). The synchronization is provided by a GPS receptor and a timing an synchronization card Odetic installed in the TCC bus. The GPS card supply time to the microsecond and a 10 KHz frequency pulse. This frequency is converted in a TTL pulse of 1 KHz sidereal by a microcontroller card. The sidereal KHz is the time base to implement the sidereal time that synchronize all the automation and the observations.

Another PC, the camera control computer (CCC), control the camera and a third one collect and record the data from the meteorological sensors the MDC. All three PC's are interconnected via a LAN served by a fourth PC running in linux, this disposition will be able the CMASF remote control when the CUC telephonic system will be connected to Internet. In the figure 1 is showed an scheme of the CMASF complete system.


The CMASF automation is divided in several subsystems, they are mainly:

1.1 The setting

The setting of the telescope works in two steps. In the first one, slew motion, after release the brake a couple of torque motors rotate the tube until set it in a position very near to the required, the rotated angle is measured by a incremental encoder.

Once reached that position the tube is braked and the fine motion began, an stepping motor acting on the brake arm move slightly the tube until the final position. While the fine motion is working the circle reading system is measuring the position of the circle in order to assure that the tube is setting in the right position. The setting take a maximum of 40 seconds with a precision better than 5 arcseconds.

1.2 The circle reading system

As was mentioned former, the declination circle is a glass circle engraved every 5'. The circle position is measured by six microscopes 60º apart one of the other. Every microscope is provided with a CCD CCTV camera, the image of the focal plane of every microscope is sequentially read by other PC (the CRC) via a frame-grabber card and then a digital image processing program compute the circle position with a precision of about 3 hundredth of arc seconds in less than two seconds.

1.3 The CCD camera

Is an Spectrasource camera with a Kodak 1600 CCD sensor of 1532x1024 pixels of 9 (, having in account the scale of the object glass a region of sky of 18'x12' is covered by the sensor. The camera works in drift scan mode, in this way an strip of sky of 18' in declination and until one hour in right ascension is scanned. It is controlled by a PC that communicate with the other PC's via the local network, in its hard disc are recorded temporally the files with the observed scans. A microcontroller card synchronized with a 10 KHz GPS frequency supply the reading rate to the camera. The transit of a celestial body through the CCD sensible surface take about 48 seconds in the equator.


Since end of 1999 December the CMASF is observing a survey of the south hemisphere until -60º. The maior priority is given to the zone -3º t0 -9º because this was the zone observed by the ROA Gautier astrographe in the "Carte du Ciel" project and there is running a joint project with the CIDA of Mérida (Venezuela) in order to remeasure the astrographic plates observed in San Fernando at the beginning of the XX century with a microdensitometer machine and, simultaneously, reobserve the zone with the CMASF in Argentina and the CCD mosaic astrographe of the CIDA. In this way it will be possible to compute good proper motions for the stars of that zone.


The results of the first six month of observation are highly encouraging, the standard deviations in right ascension and declination of two observation of the same scan are about 0".10 until 14 magnitudes, so we will expect one mean error of a final position in the range of 0".06.

In figure 2 are showed the magnitudes of the stars in one scan versus Stone's calibration zones magnitudes+ 0.4 (Stone, 1999), we add 0.4 magnitudes to Stone's values because this magnitudes are in the R band and the CMASF are computed in the V band.


Gerhel, T. Sp. Sci. Rev. 58: 347-375,1991
Stone, R.C., Pier, J.R. and Monet, D.G., Astron. J., 118: 2488-2502, 1999

Postscript versions (1, 2) of above plots.