Telescopes: An Overview

Telescopes gather light from objects, and there are two main types: refractor (uses a lens to bend light) and reflector (uses a mirror to reflect light). Aperture and field of view are two main parameters of telescopes.



Parallax is the apparent shift in position of an object because of a change in the point of view. Closer objects have a larger parallax than farther objects.


Color and Temperature

Star color is based on its temperature (hotter stars are blue, while cooler stars are red), and the color/temperature of a star can be classified into stellar classes


Wien’s Law

Wein's Law relates light intensity to temperature, stating that the peak wavelength is the inverse of temperature, and temperature and intensity are directly correlated.

Light Curves

Light Curve O-C Diagrams

The O-C, or Observed-Computed method studies period changes in variable stars by comparing the observed time of maximum brightness to the computed time. The O-C method is reflective of the cumulative effect of period changes.

CCD Imaging

Image Reduction – Overview

Image processing goes through pre-processing (calibrating images using darks, biases, and flat-fields) and post-processing (When images are digitally reduced: WCS Coordinates, removal of Cosmic Rays, Transformed, etc)

CCD Imaging


Airmass is the path length for light from an astronomical object to pass through the Earth’s Atmosphere, and a greater airmass means dimmer targets


Stellar Motions

Stellar motions divide star movement into three categories: radial motion, proper motion, and a combination of the two (space motion).


Celestial Coordinates

Similar to latitude and longitude, Right Ascension and Declination define the celestial coordinate system used to locate and place celestial objects.


Instrumental Magnitude

Instrumental magnitude is derived from the raw counts of a CCD image, and can be combined with other measurements to achieve both apparent and absolute magnitude.