gswork wrote:
I used the same calculations on nearby stars to fully appreciate why
we just can't see them as disks through telescopes, i roughly
estimated that seeing Sirius A as a disc roughly the size of the moon
would require x300,000 magnification (but i may have that wrong):

Strictly speaking, you'd be magnifying the airy disk to the apparent size of
the Moon. Brian Tung, in his response, brought up a couple of stars with
apparent sizes in the vicinity of 0.05-arcsecond. You'd need a 100-inch
aperture and incomprehensibly perfect seeing to even have a shot at visually
resolving such an object.

Based on the magnification you're applying to Sirius A, it appears you're
assuming an angular size for that star of 0.006-arcsecond. Resolving this star
visually would require a 1,000-inch (25-meter) aperture and...well, you'd need
to be above the atmosphere for seeing that good ;o)

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
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