Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar diameter with 2012 Venus transit   The role of Venus and Mercury transits is crucial to know the past history of
the solar diameter. Through the W parameter, the logarithmic derivative of the
radius with respect to the luminosity, the past values of the solar luminosity
can be recovered. The black drop phenomenon affects the evaluation of the
instants of internal and external contacts between the planetary disk and the
solar limb. With these observed instants compared with the ephemerides the
value of the solar diameter is recovered. The black drop and seeing effects are
overcome with two fitting circles, to Venus and to the Sun, drawn in the
undistorted part of the image. The corrections of ephemerides due to the
atmospheric refraction will also be taken into account. The forthcoming transit
of Venus will allow an accuracy on the diameter of the Sun better than 0.01
arcsec, with good images of the ingress and of the egress taken each second.
Chinese solar observatories are in the optimal conditions to obtain valuable
data for the measurement of the solar diameter with the Venus transit of 5/6
June 2012 with an unprecedented accuracy, and with absolute calibration given
by the ephemerides.

12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio