Annular Eclipse of 22 August 1998
IOTA February 26 1998 Eclipse Observations
Espenak homepage summarizing 1998 observations
Jay M. Pasachoff (Williams College, Williamstown,
Massachusetts, U.S.A.), Aruba. Senior Colleagues:
Bryce Babcock and Stephan Martin (Williams College), Lee Hawkins
(Wellesley College and Keck Northeast Astronomy Consortium),
Jonathan Kern. Students: Timothy McConnochie
'98, Mac Stocco '98, James Bates '98, Johan Kongsli '98, Laura
Brenneman '99, Craig Westerland '99, Lisa Reinker '99 (exchange
student from Wellesley College), Carolina Artacho '98 (Keck
Summer Fellow from Bryn Mawr College). Collaborating: Robert
Eather and John Weiley.
(a) search in the coronal green line for high-frequency coronal oscillations as a source of coronal heating (Pasachoff, Babcock, McConnochie);
(b) coronal temperature map through ultraviolet images and polarization at wavelengths chosen to maximize temperature sensitivity (Pasachoff, Hawkins, Babcock, Artacho);
(c) image to match SOHO LASCO continuum filter and field of view to calibrate scattered light in coronagraph C1 (Pasachoff, Martin).
(d) radial filter photography (Kern)
(e) IMAX movie (Eather, Weiley)
(f) eclipse photography
Accompanied by several undergraduate students from Williams College and sister institutions. Sponsored by the National Science Foundation, the Committee for Research and Exploration of the National Geographic Society, and, for some of the undergraduate support, the Keck Northeast Astronomy Consortium.
Results: Though clouds plagued the partial phases, the sky was completely clear during totality. We were at the north part of Aruba (2 min 57 s between the diamond rings) and we understand that the south part, with maximum totality (3 min), was also clear. I heard that some people in the middle, at the main town, lost the last half minute of their 3 min 15 s.
Detailed information on the Williams College Expedition is also available.
Dr. R. A. Gulyaev (Solar-Terrestrial Physics of IZMIRAN, Russian Academy of Sciences) and P. V. Shcheglov (Sternberg Astronomical Institute, Moscow State University)
Experiment on the search for the outer boundary of the dust-free zone around the Sun using the resonance emission lines of the Ca II - ion.
The apparatus: Interferometric camera with Fabry-Perot etalon
and interference filter.
The lens: F/1.65 with F = 50 mm.
Film: KODAK T-Max 3200.
Barrie Jones (Open University, UK), Curaçao, array of photodiodes for shadow-band photometry.
Serge Koutchmy (Institut d'Astrophysique, Paris), Guadeloupe
Site: near Guery (Grande-Terre, Guadeloupe; Long= 61gr30'W; Lat= 16gr29'N)
A- Morphological Imaging Analysis using different cameras put at several locations to increase the probability to get a good resolution over a large fov. Photographic film is used: film-sheets 18x13 cm (focus: 1.5 m) with a radial neutral filter of 100 mm diam.; 120 and 135 type roll films with different focal lengths cameras and telescopes (800 to 3000 mm). A priority is put on the analysis of the inner and the intermediate corona with color films to get both the cool and especially the hot fully ionized components. A 1 arcsec effective resolution is looked for.
B- Spectroscopic analysis of the corona using low spectral resolution slit- spectra at different positions and radial distances (+/- 3 Ro) covering a large spectral range on each spectrum, from UV to IR. Different spectrographs, detectors and mounts will be used.
C- Collaborative studies:
C1- In collaboration with the team of NSO/SP (leader: R. Smartt), a green line (Fe XIV) polarisation exp-t using a CCD detector will be attempted;
C2- In collaboration with the IZMIRAN team (leader: M. Molodensky) a white-light polarisation experiment will be performed.
The aim of A is to provide additional material to SoHO observations focussed on the physics of the inner corona (heating; cooling; dynamics and ejections) in order to measure the density structures at small scales thanks to
i/ precise calibration available at total eclipses;
ii/ precise polarimetric data given by multiple positioning of the linear polarizer and
iii/ colorimetric index measurements.
White-light loops and plumes are the favorite white-light structures to be studied but the search of intermediate temperature plasmoids and the relation to the highly dynamical transition region and cooler structures is another topic we consider.
The aim of B is to concentrate on the simultaneous measurement of both the electron and ion temperatures using the measurements of forbidden lines and using the Grotrian's method for electrons (smearing of the F spectrum by Thomson's scattering). The long slit crossing the whole corona (and eventually the Moon) will provide a limited spatial resolution good enough to measure the radial gradients of temperatures and subtract the F-component. The IR part of the spectra will also be recorded, up to 1.1 micron. Large scale temperature inhomogeneities in the inner 1st solar radius distance will be analyzed all around the Sun in an attempt to understand the origin of the wind.
The aim of C1 is to provide a good coverage of the green line measurements in the intermediate corona, including a magnetic field sensitive analysis of the linear polarisation. The C2 experiment is aimed at providing some 3D understanding of the white-light coronal structures.
Time of observations:
Totality is expected from 18:31:05 to 18:34:00 UT on Feb. 26, 1998;
eclipse magnitude is 1.040; height of the Sun: 49 deg.
Request for SoHO observations:
a- EIT full disk image in 304 (HeII/SiXI) at 18:32:30 UT (+/- 1 mn);
b- EIT full disk images in coronal lines taken at +/- 15 mn that time;
c- LASCO-C1 images in Green line (530.3 nm) taken near 18:30 +/- 15 mn
possibly with polarisation analysis;
d- LASCO-C2 and C3 images using the synoptic program at the same time as c.<br.
Serge Koutchmy, e/mail: firstname.lastname@example.org
Everything has gone beautifully here ! A very clear sky and a corona close to our predictions ! Many exp-ts did work properly and some new results are expected. Evaluations are begining.
V. K. Verma (U.P. State Observatory, Naini Tal, India): Latin America, CCD observations of the corona with Fe X, Fe XIV, and Ca XV filters
Jagdev Singh (Indian Institute of Astrophysics, Koramangala,
We conducted two experiments during the 1998 eclipse from a location in Venezuela. The experiments are:
(i) High frequency multi-channel photometry of solar corona:
We plan to put up 6 R647 Photomutiplier tubes at six locations in the solar corona;two in the east, two in the west and two in the north direction. The three inner tubes will be obseving at 1.2 solar radius and the outer tubes will be at 2.0 solar radius. The outer tubes will be in radial direction with respect to inner tubes. The aperture will subtend an angle of 10 arcsec. in the sky. The intensity at all the location will be recorded at a frequency of 20 Hz. The data will be used to study the intensity oscillations in the solar corona.
(ii) High resolution multi-slit spectroscopy of solar corona:
The spectra in two coronal emmision lines namely 7892 A and 6374A will be obtained at a dispersion of about 2.5 A /mm . The spectra will be recorded using Photometrics CCD camera of 1024 x 1024 format. The data will be used to determine the non-thermal broading of emmision lines and role of turbulence in heating the solar corona.
We are sending two parties to Venezuela and Guadeloupe. Our
objectives are as follows:
i) determination of the temperature of the corona by the method of different smoothing curves of coronal continuum depending on coronal temperature, by observing the K corona with a filter,
ii) polarization of the corona,
iii)morphological study of the corona by using photographic cameras with a 15 cm telescope(f=1050mm),
iv)time change of the coronal intensity of the fine structure using a CCD camera.
Frederic Clette (Observatoire Royal de Belgique, Belgium)
Main observing site : NW of Curaçao Island (Kadushi Cliffs),
altitude = 0m.
Team : about 20, 4 professionals working together with a group of amateur astronomers (experienced eclipse chasers).
white-light polarization (photographic) :
70/1000mm refractor, 6-position linear polarizer, 24X36 Tmax emulsion, two sites (Curaçao, Colombian mountains)
purpose : absolute determination of the electron density distribution from 1 to 3 Rsun (ongoing program since 1973, using the same basic instrument for continuity).
white-light polarization (CCD) :
760x580 pixel array, video output with pixel-clock synchronization, 8-bit digitization (3 exposure ranges), rotating linear polarizer with continuous image readout (0.5 to 2 Hz) givin a minimum of 12 images over a 1800 rotation, 200mm/f-2.8 telelens.
purpose : same as photographic experiment, but with a higher accuracy (in particular for the polarization angle). This is an upgrade version of this experiment which was already carried out successfully in 91 and 94.
Other experiments :
white-light photography (70/1000 refractor, Tmax 100 fine-grain emulsion) : high-resolution imaging, coronal morphology, complementary calibration for polarization analysis.
infrared photography (300 or 600 mm telelens, HS Infrared emulsion, two sites : Curaçao, Colombian mountains) : extended corona (F) beyond 3 Rsun.
meteorological station (datalogger, measurements : insolation, temperature, relative humidity, pressure) : this station was already used in 91 and 94.
Voyto Rusin (leader), Lubo Klocok, Peter Zimmermann,
(Astronomical Institute, Slovak Academy of Sciences)
1. A 100/1000 mm refractor (both the black and white, and slide films: T-grain emulsion, size 6x6 cm)
2. 500mm/8.0 telelens (slides, size 24x36mm)
1. Multicolour photometry up to 5-7 solar radii (electron density, temperatures)
2. Small and large-scale structure of the white-light corona
3. Fast changes in the corona, if any, through camcoder
Shadia Habbal, R. Esser, S. Fineschi, and A. Mossman
(Harvard-Smithsonian Center for Astrophysics); M. Guhathakurta
and R. Fisher (Goddard SFC/NASA); J. Johnson (Electricon); M.
Arndt (UNH), and R. Woo (JPL).
Photometric obesrvations of the corona in the visible wavelengths of the Fe lines: 7892, 6374, and 5303 A. Data will be recorded on both CCD and photographic cameras. Polarization measurements from Guadeloupe will be coordinated with SOHO, VLA, and radio occultation measurements during the superior conjunction of the spacecraft Galileo, which is orbiting Jupiter. The radio occultation measurements will probe the corona on a spatial and temporal scale that cannot be achieved with imaging instruments.
Bob MacQueen (Rhodes College), Jeff Kuhn (National Solar
Observatory and Montana State University), Ingrid Mann
(Max-Planck Institut), Haosheng Lin (National Solar Observatory),
Phil Judge (High Altitude Observatory), and Dan Edmunds (Montana
Airborne experiment to measure the first 1-5 micron IR spectrum of the corona and to measure new properties of the circumsolar dust cloud. Operated from an open C-130 aircraft airborne west of Panama.
Haosheng Lin (National Solar Observatory), Jeff Kuhn (National
Solar Observatory and Montana State University), Matt Penn
(National Solar Observatory), Steve Tomczyk (High Altitude
Observatory), and Phil Judge (High Altitude Observatory).
A near IR imaging spectropolarimeter to measure the coronal magnetic field by making very sensitive Zeeman observations of an infrared Fe XIII emission line. Curaçao.
Before getting caught up with teaching I promised to write a brief summary of the aircraft eclipse experiment from Panama:
On thursday, the day of the eclipse, we arrived at Howard airforce base before 7:00am (Carnaval had just ended) in time to study the satellite imagery the Howard AFB weather group was gathering for us. Growing cirrus clouds to the west of Panama left few options but to choose our primary intercept point with the moons shadow at a far rendezvous point, 800km into the Pacific. We decided to approach this intercept by flying southwest along the computed eclipse path trajectory. We arrived at our second contact point early enough to complete additional calibration, and we "waited" for the lunar shadow by executing a standard aircraft holding pattern at about 18,000 ft. The shadow arrived on time, and with the C130 properly aligned on the eclipse centerline and heading parallel to the shadow. We were rewarded with the longest period of totality (almost 5 minutes) that could be observed. All instruments and experimenters performed as designed and rehearsed, and we acquired data with few technical disappointments. The instruments accumulated nearly 100Mbytes of data which we have now only begun to analyse. Although we have no quantitatively results we did have computers fired up on the 10 hour flight back. A quick look shows that the spectroscopic data cleanly measures IR emission lines near 1 and 1.43 microns. If there is coronal HeI it is very weak, as are other emission lines out to 2.2 microns. The spectroscopic F-coronal signal will take more time to analyse. The photometric data shows high S/N J and K band F-coronal signal over the full 6 degrees of the field-of-view. There is also an interesting signal at 3.9 microns which we are anxious to track down when computers and data are once again available. In short the data appears to be exceptional and unique -- we are optimistic about realizing the scientific goals of the mission.
Jeff Kuhn (for the C130 eclipse experiment group: Bob MacQueen, Ingrid Mann, Haosheng Lin, Jack Streete, Dan Edmunds, Phil Judge, Peter Hillebran, and Gerry Tansey)
The full text of the report can be found here.
Subject: [SE] Antigua
Twelve people (11 students, 1 teacher) from the University of Northern Iowa went to Antigua for the eclipse. The group at Jolly Harbour was clouded out between 2nd and 3rd contacts, but the Shirley Heights group had clear skies. (Those of us who missed it consolled ourselves with a chartered fixed-wing fly-over of the Montserrat volcanoe.)