Question

corelate , orbit of hubble telescope

Answer 1

Hubble is classified as a Cassegrain reflector, named after a 15th century French cleric who was among the first to suggest this basic optical design. Light hitting the telescope’s main, or primary mirror is reflected to a smaller, secondary mirror suspended above the primary. The secondary, in turn, reflects the light back through a hole in the primary where it enters Hubble’s instruments (cameras and spectrographs) for final focus before it hits their detectors. Hubble’s primary mirror is not only exquisitely polished, but at 94.5 inches (2.4 m) in diameter, collects an immense amount of light. Hubble can detect objects that are 10 billion times fainter than the unaided eye can see. High above the blurring effects of Earth’s atmosphere, Hubble also gets a much clearer view of the cosmos than do telescopes located on the ground. The space telescope can distinguish astronomical objects with an angular diameter of a mere 0.05 arc seconds — the equivalent to discerning the width of a dime from a distance of 86 miles. This resolution is about 10 times better than the best typically attained by even larger, ground based telescopes. High resolution enables Hubble to locate such objects as dust disks around stars or the glowing nuclei of extremely distant galaxies.

Also because it circles above the atmosphere, Hubble can view astronomical objects across a wider range of the electromagnetic spectrum than ground-based telescopes, which are limited by atmospheric absorption at various wavelengths. This gives astronomers using Hubble a fuller view into the energetic processes that create the radiation seen and measured.

Finally, Hubble’s observations are predictably consistent. The telescope’s seeing conditions do not change from day to day or even orbit to orbit. Astronomers can revisit targets with the expectation that they will be imaged at the same high quality each time. This optical stability is critical for detecting tiny motions or other small variations in celestial objects. Such is not the case for ground-based observatories, where observing conditions vary with weather and directly affect the quality of the images acquired.