ABSTRACT A total of 3350 objects from the Sixth Catalog Orbits Visual Binary Stars (ORB6) are investigated to validate Gaia Early Data Release 3 (EDR3) parallaxes and provide mass estimates for systems. We show that two-thirds binaries with a separation 0.2–0.5 arcsec left without parallax solution in EDR3. Special attention is paid 521 pairs known separately each component. find 16 entries dee...

A sample of subdwarfs with accurate space velocities and stan-darized metallicities is presented. This was constructed by combining Hip-parcos parallaxes and proper motions with radial velocities and metallicities from Carney et al. (1994; CLLA). The accurate Hipparcos parallaxes lead to an-upward-correction factor of 11% of the photometric distance scale of CLLA. The kinematical behaviour of t...

Impostors are image-based primitives commonly used to replace complex geometry in order to accelerate the rendering of large virtual environments. This paper describes a “layered impostor technique” used for representing distant scene-parts when seen from a bounded viewing region. A special layer placement is derived which bounds the geometric error introduced by parallaxes to a defined value. ...

We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1R and FGS 3, white-light interferomet...

Relations are given for the correction of bias when mean absolute magnitudes are derived by the method of reduced parallaxes. The bias in the case of the derivation of the absolute magnitudes of individual objects is also considered.