[vsnet-chat 1083] Re: (fwd) IP Peg eclipse timing (Masi)

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Dear Dr. Kato,

> 
>    Well, although the discrepancy in heliocentric correction between us
> has been reduced to 5 sec, it will be still significant in fine analysis
> of eclipsing CVs.  Five seconds roughly corresponds to 0.01 AU, which
> difference looks too large for any (even rough) conventional ephemeris
> of the earth.  Does Binnendijk's formula correctly treats the eccentricity
> of the earth's orbit?


I report here, for reader convenience, the Binnendijk's formula:

H.C.= -0.0057755*(R*cos(theta)*cos(alpha)*cos(delta)+
R*sin(theta)*(sin(obl)*sin(delta)+cos(obl)*cos(delta)*sin(alpha)))

It is espessed in days.

R= Sun-Earth distance, in U.A.
theta=sun longitude
alpha, delta= equatorial coordinates of the star
obl=mean obliquity of the ecliptic

ALL THESE DATA HAVE TO BE REFERRED TO THE DATE OF INTEREST.

The earth's orbit eccentricity is not directly present in the formula
above, but it is used to find theta and R. The eccentricity is evaluated
from a formula that takes into account time evolution of this parameter:

e=0.01675104-0.0000418*T+0.000000126*T*T

with T=(JD-2415020.0)/36525

On my books I have found that the Binnendijk's formula gives an estimate
for the H.C. (I don't know how precise yet). 

As regards the correction for the barycentric JD, I've read that its
principal term is due to Jupiter and it is of the order of 4/5 secs. 

Sincerely,
Gianluca




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* Gianluca Masi                           "Two things fill the soul   *
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* 03023 Ceccano (FR)                     the starry sky above me and  *
* ITALY                                    the moral law within me"   * 
* email: gianmasi@fr.flashnet.it                                      *
* http://vsnet.eurolink.it/comets/                        I. Kant       *
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