The Caldwell Objects

you see its core dancing? Its starlike center seems
to jump around. That's because the core is
surrounded by a thin shell of light, which is
surrounded in turn by a fainter, circular
envelope. As your eye moves around the field
involuntarily, various parts of these dense halos
waltz into view. High magnification does not
improve the view much. With time you should
make out some concentrations of light forming a
cross that marks the main cardinal directions.
These glows may be superimposed field stars of
roughly 14th magnitude; the brightest lies just
northeast of the cluster's core. Look for a dim arc
of light at the northeastern edge of the cluster's
outer halo.
Larger instruments do not seem to enhance
the view much. Christian Luginbuhl and Brian
Skiff report that the core and inner
66
halo look granular through a 12-inch. Ernst
Hartung failed to resolve NGC 5694's constituent
stars, seeing only a "conspicuous round
symmetrical haze, well condensed towards the
centre." And Barbara Wilson couldn't fully
resolve the cluster in a 20-inch f/4 reflector at 72x,
though she did resolve about 30 percent of it,
reporting some faint 15th-magni-tude stars. But I
would not give up hope. Like planetary nebulae,
tight globular clusters can take magnification
well on steady nights, and I believe partial
resolution can be achieved in a good 8- to 10-inch
telescope (and in a 4-inch under very dark skies).
I also suspect that anyone using a moderately
long-focus refractor could better resolve this
globular cluster if they use higher magnifications
— say 800x to 1,000x — on nights of superb
seeing. So give it a go.
The Caldwell Objects 265