Spatial Resolution

The distribution of spatial resolutions instruments tend to use is shown in Figure 4. Working from left to right in this plot, the instruments using very fine plate scales are generally fed by AO systems, which of course typically yield near diffraction-limited point spread functions (PSFs) that are nearly an order of magnitude smaller than seeing limited PSFs. Interestingly, if the same poll were cast a decade ago, the plot in Figure 4 would not have included many instruments with plate scales measured in units of milli-arcseconds simply because adaptive optics was not widespread enough to drive the development a significant population of AO specialized instruments.

Plate Scale [arcsec/pixel]

Figure 4. The distribution of plate scales for all of the instrumentation sampled in the survey.

Plate Scale [arcsec/pixel]

Figure 4. The distribution of plate scales for all of the instrumentation sampled in the survey.

Today, however, AO systems are becoming commonplace and modern research is conducted at spatial resolutions that were previously impossible to achieve. The peak in the distribution at ~0.1" is a bit surprising. On the assumption that most instruments are sampling seeing limited images (~1") at the Nyquist limit, a peak closer to ~0.5" is expected. The dearth of instruments using large pixels (>0.5") is probably due to a bias built into the survey, which was restricted to 3.5 m telescopes or larger. If it included the large number of ~1-3 m telescopes in use today, which are often wide field systems, the right end of the histogram in Figure 4 would have included many more instruments.

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