If primary beam of antenna is >> solar diameter,
then imaging is easy.
If primary beam of antenna is << solar diameter,
imaging of small regions in the disk is
relatively easy.
If primary beam of antenna is comparable to the solar diameter, good imaging is hard.
Pointing is most critical
Short spacing measurements become very important for good imaging
Short spacing measurements are hard to obtain in this regime (cant get the antennas close enough together).
Calibration may set a minimum size of antenna.
An important design choice, tied to array
configuration.