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High resolution solar observations at the Pic du Midi Observatory
Adv. Space Res. Vol. 11, No.5, p. (5)149, 1991 Printed in Great Britain. All rightsreserved.
0273—1177/91 $0.00 + .50 Copyright © 1991 COSPAR
HIGH RESOLUTION SOLAR OBSERVATIONS AT THE PlC DU MIDI OBSERVATORY R. Muller and Th. Roudier Observatoire Midi-Pyrénées, URA 1281, 65200 Bagnères de Bigorre, France
PlC DU MIDI SITE QUALITY Observations of the solar photosphere and chromosphere are performed at the Plc du Midi Observatory (elevation, 2860 m) with a 50 cm refractor (Coupelle “Tourelle”). The atmosphere can be continously stable for few hours in the morning. During those moments of very high seeing quality, many frames taken with an exposure time of 5 msec reach the diffraction limit of the refractor 0” .25 over a field of view larger than 100”xl 00”. The statistics of the image quality established from 1970-1976, using the quality scale of the JOSO site testing compaigns (Q = 0 High quality, free of seeing), give: Exceptional atmospheric stability occurs 5 to 10 days a year providing 10 to 20 hours of excellent seeing (0”.25) over a large field of view (1’ x 2’). —
The quality 1 or 2 (granulation is well visible) occurs 50% of the time during the 3 first hours in the morning and 40% until 12h (local time). —
Superb seeing conditions occur when the wind blows gently in the NE direction; the presence of snow is a stabilizing factor, increasing the duration of the high seeing conditions. In the NE direction, the Pic du Midi is 600 meters higher than the nearly mountains and 100 meters above the valley. The Air mass at the level of the Pic du Midi is thus not disturbed when it is blowing in this direction. The seeing conditions at the Pic du Midi are very favorable for the observations and study of the smallest solar features, and especially of their evolution. The focus instrumentation consists of a 35 mm movie-camera (filtergrams) and an echelle-spectrograph, which can be used either in the conventional mode (single pass) or in the double pass mode as a Multichannel Soustractive Double Pass Spectrograph (M.S.D.P.).
Filtergrams are taken in white light at 5750 1 and in the CH band at 4308 t, where Network Bright Points and Faculae are visible even at the disk center. Bursts of about 50 frames are taken at a speed of 24 frames per seconde. The best ours are then selected. Granulation, Bright Points, Faculae and sunspot evolution movies can thus be obtained up to 5 hours long. 2D MSDP spectrograph is used to analyse filament, granulation, flare dynamics. Such hind of observations provide the line profile in each point of the field of view. Thus the intensity and velocity fields can be analysed simultaneously. The spectograms (2D) are generally taken in the NaD2 5696 photospheric line and Ha line; the dispersion is 4.5 mm/A; exposure time 1/4 sec a 70 nun camera is used. I,, the simple pass mode (slit-jaw spectrograph), spicule, granulation and sunspot are observed in one wavelength range. In order to measure the solar diameter at all heliographic latitude and its variation during the activity cycle, an heliometer has been built and carried by the “coupole Tourelle” 50 cm refractor. The diameter is measured at the inflexion point of the limb. The instrument has produced hundred seans clean enough to
0273—1177/91 $0.00 + .50 Copyright © 1991 COSPAR
HIGH RESOLUTION SOLAR OBSERVATIONS AT THE PlC DU MIDI OBSERVATORY R. Muller and Th. Roudier Observatoire Midi-Pyrénées, URA 1281, 65200 Bagnères de Bigorre, France
PlC DU MIDI SITE QUALITY Observations of the solar photosphere and chromosphere are performed at the Plc du Midi Observatory (elevation, 2860 m) with a 50 cm refractor (Coupelle “Tourelle”). The atmosphere can be continously stable for few hours in the morning. During those moments of very high seeing quality, many frames taken with an exposure time of 5 msec reach the diffraction limit of the refractor 0” .25 over a field of view larger than 100”xl 00”. The statistics of the image quality established from 1970-1976, using the quality scale of the JOSO site testing compaigns (Q = 0 High quality, free of seeing), give: Exceptional atmospheric stability occurs 5 to 10 days a year providing 10 to 20 hours of excellent seeing (0”.25) over a large field of view (1’ x 2’). —
The quality 1 or 2 (granulation is well visible) occurs 50% of the time during the 3 first hours in the morning and 40% until 12h (local time). —
Superb seeing conditions occur when the wind blows gently in the NE direction; the presence of snow is a stabilizing factor, increasing the duration of the high seeing conditions. In the NE direction, the Pic du Midi is 600 meters higher than the nearly mountains and 100 meters above the valley. The Air mass at the level of the Pic du Midi is thus not disturbed when it is blowing in this direction. The seeing conditions at the Pic du Midi are very favorable for the observations and study of the smallest solar features, and especially of their evolution. The focus instrumentation consists of a 35 mm movie-camera (filtergrams) and an echelle-spectrograph, which can be used either in the conventional mode (single pass) or in the double pass mode as a Multichannel Soustractive Double Pass Spectrograph (M.S.D.P.).
Filtergrams are taken in white light at 5750 1 and in the CH band at 4308 t, where Network Bright Points and Faculae are visible even at the disk center. Bursts of about 50 frames are taken at a speed of 24 frames per seconde. The best ours are then selected. Granulation, Bright Points, Faculae and sunspot evolution movies can thus be obtained up to 5 hours long. 2D MSDP spectrograph is used to analyse filament, granulation, flare dynamics. Such hind of observations provide the line profile in each point of the field of view. Thus the intensity and velocity fields can be analysed simultaneously. The spectograms (2D) are generally taken in the NaD2 5696 photospheric line and Ha line; the dispersion is 4.5 mm/A; exposure time 1/4 sec a 70 nun camera is used. I,, the simple pass mode (slit-jaw spectrograph), spicule, granulation and sunspot are observed in one wavelength range. In order to measure the solar diameter at all heliographic latitude and its variation during the activity cycle, an heliometer has been built and carried by the “coupole Tourelle” 50 cm refractor. The diameter is measured at the inflexion point of the limb. The instrument has produced hundred seans clean enough to