Title:
A study of the astronomical seeings at two sites of Kunming and Lijiang
Authors:
Qian, T. L.; Qiu, C. R.; Cen, X. F.; Wang, J. C.; Xu, J.; Wang, C. Y.
Journal:
Acta Astronomical Sinica, vol.42, no.1, p.101-111.
Publication Date:
02/2001
Abstract
:
The seeings of two sites at Yunnan Observatory of Kunming and Gaomeigu Station of Lijiang are studied by using the three sub-aperture DIMM of Yunnan Observatory. The FWHMs given by 1
m telescope and the seeing measured by DIMMs are compared. In terms of the simultaneous data of seven days' observations, the average FWHMs of 1 m telescope is 1.17", while the average
seeing of DIMM is 0.84". The authors tested the effect of time exposure on the measured seeing of three sub-aperture DIMM and found that the seeing of 20 ms time exposure is 15% better than
that of 8 ms time exposure. From May 1995 to December 1996 the authors compared observations of two sites and obtained the data of 234 nights in Gaomeigu and of 256 nights in Yunnan
observatory. The average seeings of two sites are, respectively, 0.70" at Gaomeigu and 0.95" at Yunnan Observatory. The seeing variations with time of the two sites are also studied.
Excerpts of a letter from Dr. Cen Xuefen (YUNNAN Obs.) to M. Sarazin (May 5, 1996):
On April 5,6,7 1996, a conference on site testing of
the Chinese Large Telescope was held. The site selection WG reported
results of Cloud Cover, meteorological conditions, seeng conditions,
water vapour content, sky brightness and extinction.
From May 95 to May 96, the Fried parameter r0 was measured with an
average value of 16cm on Gaomeigu site, by a DIMM attached to the 35cm
telescope on 3m high tower, corresponding to an image FWHM of around
0.7". While the value of r0 is 12cm at Yunnan observatory.
The site selection will continue at least one more year at Gaomeigu.
Three new programs are proposed, two 30m towers instrumented with
anemometers and microthermal sensors will be set up at the end of this
year for measuring the seeing of ground levels. A 60cm reflector
telescope will be mounted on 10m tower in order to reduce the effect of
ground turbulence and do some astronomical programs. Two acoustic
sounders will be used for estimating the seeing from 10m to 1000m
above ground (....)