Double Star Vocabulary
Adapted from Kalée Tock and Ryan Caputo
This page contains key terms and concepts used in double star astronomy. As you watch the introductory video, use the explanations to write brief definitions for each term in your research notebook. Understanding this vocabulary is essential for conducting your double star research.
Observation Terms
Double star:
Binary:
Optical double:
Primary star:
Secondary star:
Measurement Concepts
Position Angle (PA):
Separation (Sep):
Arcsecond: (Note: The symbol for arcseconds is ″. This is not the same as a double quote symbol, ".)
Visual micrometer:
Centroid:
Measurement aperture:
Point Spread Function (PSF):
Astronomical Measurements
Astrometry:
Photometry:
Parallax (Plx) (include units!):
Milliarcsecond (mas):
Proper Motion in RA (PM RA) (include units!):
Proper Motion in Dec (PM Dec) (include units!):
Motion and Dynamics
Proper motion versus orbital motion:
Kepler's 3rd Law:
Short-arc binary:
Ephemeris:
Escape velocity:
Transverse separation:
Radial separation:
Formula for radial distance from parallax:
Observational Factors
Seeing:
Saturated:
ADU counts:
Stacking:
Research Terms
JDSO:
Color-Magnitude Diagram (CMD):
Target Selection
Best RA for Observation: Please describe below how you will make sure that your target is currently visible (i.e., not behind the Sun at this time of year).
Next Steps
After familiarizing yourself with these terms, you'll be ready to select your double star target for observation and measurement.