SOLAR

RESEARCH

ASTROPHYSICAL

AT THE CATANIA OBSERVATORY

(Report from Solar Institute)

G. GODOLI (Received 24 April, 1969) 1. History and Location

The first building of the Catania Astrophysical Observatory (OAC) was erected by Tacchini on Mount Etna between 1879 and 1880 at 2942 m above sea level. Later on, in 1885, a main office was established near the city boundary (at that time) of Catania. Today the OAC consists of four establishments: (1) the old main office used for archives (latitude 37~ N, longitude 15~ E, altitude 49 m above sea level); (2) the new main office on the Catania University ground (latitude 37~ N, longitude 15~ E, altitude 193 m above sea level); (3) the heliophysical station at Sant'Agata Li Battiati (latitude 37~ N, longitude 15~ E, altitude 348 m above sea level); (4) the stellar station at Serra La Nave (latitude 37~ N, longitude 14~ E, altitude 1725 m above sea level). For a long time observations of solar activity have been made at the OAC. In the observatory's file are drawings of sunspots and faculae which were made in Palermo, starting in 1865. The Palermo drawings made daily cover the period February 22nd 1871-December 31st 1891. Since January 1st 1892 drawings of sunspot pores, sunspots, faculae have been made daily in Catania. In the file are also drawings and data of prominences observed at Palermo during the period March 10th 1871-December 31 st 1890. Since December 12th 1891 drawings of prominences have been regularly made in Catania. During the period March 3rd 1913-December 31st 1964 observations of prominences were made with a Zeiss spectroscope. The results of these observations have been published periodically. For the 18th, 19th and 20th cycles the position, type and area of sunspots were determined yearly. The data for the years 1953-1966 have been published. Since 1962 systematic flare observations with Ha Halle filter No. 36 and successively No. 78 have been made. The results of these observations have been periodically published. Since February 1964 daily spectroheliograms in the K2,3,2 line have been made with a new small spectroheliograph designed by Prof. Fracastoro. From the photographic plates characteristic numbers for Ca plages have been regularly determined and published yearly. 2. Weather Conditions

The annual number of days on which patrol observations of short duration can be made is very large. In 1968 this number was 355. Solar Physics 9 (1969) 246-249; 9 D. Reidel Publishing Company, Dordrecht-Holland

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The annual number of hours of sunshine is 2900 (measured during the two-year period 1967-1968). Solar seeing seems to be very good during long periods. Further seeing quality analysis by optical and microthermal observations are being made at the new head-office, at Sant'Agata Li Battiati and in the extreme southern part of Sicily (Isola delle Correnti, 36o39' N, 15~ ' E).

3. Staff (1969)

The Catania Astrophysical Observatory is a Government Institution financed jointly by the Ministry of Education, by the National Research Council and by Catania University. Therefore the staff includes members appointed by the above-mentioned bodies. The staff is formed of ten scientists: C. Blanco, F. Catalano, S. Catalano, S. Cristaldi, G. Godoli (director), O. Morgante, M. Narbone, L. Patern6, M. Rodon6, M. L. Sturiale; eight observers, five technicians, five calculators, besides eight people empioyed in administration, secretarial and general services. Part of this staff is partially or completely engaged in stellar research directly connected with solar problems (see section 5). The director is full professor of astronomy at Catania University. Lectures on astronomy, astrophysics, space physics are held at the observatory for students graduating in physics and mathematics.

4. Solar Instrumentation

White light drawings and pictures are made at the Cooke refractor 15/223 situated at Sant'Agata Li Battiati. On the same mounting, an optical train for an Ha filter is arranged. The spectroheliograph is fed by the Steinheil refractor 33/347 still situated near the old head-office. A 87.4 MHz radiometer is situated on the top of the new head-office. At the new head-office a small solar tower is operating mainly for laboratory purpose. 5. Research Programmes

Historical tradition, weather conditions and available instrumentation strongly suggest, for the solar work at OAC, a research programme based on the solar activity patrol. At present this patrol includes the following observations: (a) Photosphere. (al) Daily drawings of sunspot pores and sunspots; drawings of equatorial and polar faculae during days of particularly good seeing. (a2) Hourly heliograms of the photosphere. (b) Ha chromosphere on disc. Daily continuous observation with Halle filter (passband 0.5 A.). One filtergram/5 m is taken.

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G.COOOL1

(c) Hc~ chromosphere at limb. Daily continuous observation with Halle filter (passband 1 A). One filtergram/5 m is taken. (d) K chromosphere on disc. Daily spectroheliograms. (e) K chromosphere at limb. Daily spectroheliograms. (f) Radiocorona. Continuous observations at 87.4 MHz. (g) Special events. Continuous photographic observations of special events (important flares and active prominences) between Hc~- 1 A and Ha + 1 A. From this observational material the following data are deduced and published yearly: sunspots sunspot pores equatorial photospheric faculae polar photospheric faculae He faculae K faculae flares He quiescent prominences on disc Hc~ quiescent prominences at limb K quiescent prominences at limb Hc~ active prominences on disc and at limb 87.4 MHz flux

Wolf number; position, type and area of the sunspot groups number number number characteristic number; position, area and compactness characteristic number; position, area and compactness position, area and intensity characteristic number; daily number and total apparent length position, height and area position, height and area position and importance events.

The original observations and the data are distributed as follows: Institution WDC

CI CIG Istituto naz. di Geofisica Osserv. astronomico Osserv. astronomico Osserv. astronomico

A B C C C

Material transmitted Boulder Moscow Freiburg Meudon Ztirich Roma Roma Bologna Roma Trieste

e, e, a, g, e e, e e, a, g,

f, g, h g, h b, c, d h,i g, h g, h c, d h.

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Explanation a) photospheric photograms b) photocopies of sunspot drawings c) Ha filtergrams d) copies on film of K spectroheliograms e) Wolf number, position and area of sunspots f) K facula maps; position, area, intensity and compactness g) He flare data h) Ha active prominence data i) ursigrams and adalerts. The observations and collected data have been the basis of many morphological and statistical investigations. A new research programme on stellar activity of solar type has been recently undertaken at the OAC. With the expression stellar activity of solar type we mean the manifestation of stellar activity determined by the same mechanism that determines the solar activity. It is evident that this mechanism, acting on different stars in different physical conditions, would give rise to phenomena which are quantitatively and qualitatively different. Vice versa, from the study of these phenomena, knowing the physical conditions in which they take place, we can hope to deduce new information on the mechanism involved. This programme includes theoretical research on magnetic stars and photoelectric observations of magnetic, spotted and flare stars. 6. Future Development An equatorial spar is under construction to incorporate six different optical trains for: a) photospheric visual and photographic observations; b) He chromospheric observations; c) He wing chromospheric observations; d) K chromospheric observations; e) He prominences observations; f) experiments. A spectrograph for the solar laboratory is also under construction. 7. Publications Until 1968 papers published in current Journals were distributed as Pubblicazioni delI'Osservatorio Astrofisico di Catania. As from the beginning of 1969 and following the recommendations of the IAU 5th Commision (Prague, 1967), only the papers not published in a current Journal will be distributed as Pubblicazioni dell'Osservatorio Astrofisico di Catania. We welcome all form of national or international cooperation. The OAC observational material, already distributed on a large scale, is available to all interested scientists.