Contents. planet: 6 - Saturn satellites: S12-Helene:22 total number: 22 type: relative dates: 1985-1987 observatory: 874 - Itajuba (Laboratorio Nacional de Astrofisica) Reference. Veiga C.H., Vieira Martins R. (2000) Astrometric photographic observations of Helene. Astron. Astrophys. Suppl. Ser. V. 143. P. 405. 2000A&AS__143__405V Informations. relative to: S6-Titan: 22 reference frame: astrometric centre of frame: topocentre epoch of equinox: J2000 time scale: TT reduction: no information coordinates: X, Y diff. refraction: no information receptor: photographic telescope: no information observers: Veiga C.H., Vieira Martins R. data included in standard data file: no Comments. Abstract: Astrometric photographic positions of the Saturnian satellite Helene obtained from 22 plates taken in 6 nights are presented. The observations are distributed between 5 missions in 1985 and 1987. All positions are compared with those calculated by Jacobson (1999, personal communication). The residuals have mean and standard deviation smaller than 0.25" and 0.30" respectively. evaluation: The differences O-C(X), O-C(Y) are published in the article. For these values one have: X Y M. (mean) 0.178" -0.101" R.M.S. (root mean square) 0.434" 0.250" The differences O-C(X)e, O-C(Y)e were also calculated by N.Emelianov with the theory by P. Oberty for Helene and with the theory by Harper & Taylor for Titan. With these O-C one have X Y M. (mean) -0.087" -0.181" R.M.S. (root mean square) 0.470" 0.536" Format. Bytes Format Units Label Explanations ----------------------------------------------------------------- 1- 4 I4 yr Obs.Y Year of the mean instant of observation 6 I1 --- Obs.M Month of the mean instant of observation 8- 15 F8.5 d Obs.D Decimal day of the mean instant of observation 17- 24 F8.3 arcsec X Differential topocentric coordinate, {Delta}RAcosDE (1) 26- 32 F7.3 arcsec Y Differential topocentric coordinate, {Delta}DE (1) 34- 39 F6.3 arcsec (O-C)X Observed minus calculated value of X 41- 46 F6.3 arcsec (O-C)Y Observed minus calculated value of Y ----------------------------------------------------------------- Note (1): Differential topocentric coordinates are referred to Titan. The reference system is defined by the mean equator and equinox J2000 ---------------------------------------------- Obs.Y Obs.D X Y (O-C)X (O-C)Y Obs.M arcsec arcsec arcsec arcsec ----------------------------------------------