2.7. Requirements for a Successful Monitoring Program
In order to avoid misleading systematic errors of the
sort discussed thus far, care must be taken in designing
an observational monitoring program. The fairly obvious basic requirements
that we should keep in mind are:
- The monitoring program must have sufficient sampling.
Specifically, the observations should be closely spaced
in time relative to physical time scales of interest. In terms of
total duration, the program should be at least three times as long as
the longest time scale to be investigated.
- The S/N of the light curve must be high enough
to detect variations on the shortest interesting physical
time scale. Inspection of Fig. 2,
for example, demonstrates
that if you can measure continuum fluxes to only 10% accuracy,
3 detections of continuum
variability in Seyfert 1
galaxies will be extremely rare on time scales as long as months.
- Systematic effects must be obviated. The data must
be as homogeneous as possible. The easiest way
to do this is to acquire the data with a single instrument in
a stable configuration that is suitable for all
the observing conditions expected over the duration of the program.