The above light curve of OY Carinae covers almost 10 hours and shows why CVs, with their repetitive light curves, have becoms such popular objects for the amateur CCD operator.  Data for this curve provided by Farmcove Observatory  using an LX200 10inch f/10 telescope, ST6 CCD Camera, Bin 3x3, 30 second exposures with calibration.  

The above light curve of OY Carinae covers almost 10 hours and shows why CVs, with their repetitive light curves, have becoms such popular objects for the amateur CCD operator. 

V803 Centauri is a CV of the AM Canum Venaticorum type. It comprises two white dwarfs orbiting each other in a period of 1611 seconds. This light curve shows pronounced light variations during a decline from a bright outburst.

What do we plot to make a light curve and what does it tell us? The X or horizontal dimemsion of the plot is always time. It may be seconds, minutes or days, or even 'phases' based upon the known period of the star.

The vertical or Y axis is always brightness, expressed in intensities or magnitudes. Magnitudes are brighter the smaller the number, hence brightness increases upward and time to the right.

Astronomers use Julian dates - JD - being a day number since 1 January 4713 BC at noon UT For convenience we drop the first two digits as JD 2450706 is a bit unwieldy!

V 2051 Ophiuchi is one of the few eclipsing systems in the SU Ursae Majoris subgroup of dwarf novae. This light curve shows clearly defined eclipses as well as a superoutburst feature, superhumps. These are visible immediately following each eclipse. The orbital period is 89.9 minutes. This star is a suspected polar.

At the other extreme, visual variable star observers' groups such as the RASNZ VSS and the AAVSO are engaged in observing Mira and other long period variable stars where the cycles extend up to years. One such light curve is shown, but if this is your interest you should refer to the visual observers' section. These longer period stars do show colour changes and valuable work can be done in measuring these - see Colour Photometry.

Another area of some interest is measuring the rotation periods of minor planets. A few of the larger ones are nearly spherical, with fairly unrewarding light curves, but many of the smaller ones are irregular in shape with strongly variable light curves. They shine by reflected sunlight so there is little colour change and generally periods are of only a few hours. But these need a cooperative effort from many observers, otherwise the data is 'random' and not of much value. Other areas are measures of MACHO objects and exoplanet transits.

Originally TSP was carried out with pep equipment. This has the virtue of high time resolution, but lacks the sensitivity and convenience of CCD photometry. With better cameras the time resolution of CCDs has reached the stage where they can cope with most of the tasks required of amateur observers.