Abstract
The advent of large format CCDs and mosaics has revolutionized the study of optically visible outflows from young stars. Their large fields of view led to the recognition that many Herbig-Haro outflows attain parsec-scale dimensions and dynamical time scales comparable to the accretion time of young stars. Thus, outflows provide fossil records of the major mass-loss events that have occurred during the birth of their source stars. Wide-field images have also revealed a new class of Herbig-Haro objects lit up by external radiation fields. When ionized, their physical properties can be readily determined using the nebular diagnostics of photoionized plasmas. C-shaped bends, brightness asymmetries, and jet/counter-jet velocity ratios in irradiated jets provide powerful diagnostics of the launch, collimation, and propagation of stellar jets.
