Because of its huge light-gathering power
and the sophisticated coronagraphic (starlight-blocking) capabilities of its METIS instrument, it will be able to directly image such planets around the nearest stars, says Ignas Snellen (Leiden University).
That would hardly compromise the angular resolution of the observations, but it would of course reduce the sensitivity of the instrument: With four mirrors, for example, the GMT would have the same light-gathering power
as an imaginary 17-m telescope.
The aperture (diameter) of the primary lens or mirror in your telescope determines two things: the light-gathering power
(light grasp) of the instrument and its resolving power--the ability to see fine detail in an image.
"Most telescopes have poor optics because people in the past were interested only in total light-gathering power
when they built large [telescopes]," says Kenneth J.
Despite the mediocre reflectivity of their metal speculum mirrors, these reflectors were vastly superior in light-gathering power
. Zigel reasoned that the failure to detect the presence of Phobos and Deimos was because they had been lofted into orbit around Mars sometime between 1862 and 1877.
While binoculars can show some of these things, you really need the greater light-gathering power
and magnification of a telescope.
According to the most recent plans, the NNTT would be a square array of 8-meter mirrors that could work together to simulate the light-gathering power
and resolution of a single 16-meter mirror or could work separately (SN: 1/3/87, p.10).
O III filters are fairly dense and thus work best with the light-gathering power
of at least a 4-inch telescope.
For some people it means getting a telescope with a larger lens (in the case of a refractor) or mirror (reflector), which offers greater light-gathering power
and the ability to see fainter objects.
In spite of the success, the six 1.8-meter mirrors of the MMThave the total light-gathering power
of a single mirror of 4.5 meters diameter.
I prefer observing with the refractors because of their black sky background, but the reflector does have greater light-gathering power
So are the planners of the National New Technology Telescope, which is projected to be a multiple-mirror arrangement with a light-gathering power
equivalent to a 15-meter single mirror.