"Mick" wrote in message ...
The image I see in the EP is probably 4 or 5 mm in diameter at some 200 X's
magnification...does this sound right irrespective
of the type of scope?

Actually, your statement is meaningless (unless you really mean to say
that Mars is as microscopic as what Harald calculated). How big does
5 mm look? If i hold a 5 mm bead 50 cm in front of my face, it looks
the same size as a 20 mm grape does 2 meters away.

Unless you plan to hold a *very* long tape measure against the dusty
red Martian surface, you can't talk about linear units such as
millimeters. Angular size is the only meaningful measure in this
context.

Actually, you might get a better idea of apparent sizes with that 5 mm
bead than with your TP rolls. Mars (actual size, 6,794,000,000 mm)
subtends 22.3" across the sky tonight. Magnify that 200x and you get
an image 74' across, irrespective of the type of scope. This is what
the bead looks like if you hold it 0.23 meter away. The naked-eye
Moon should appear the same size as the bead at 0.54 meter. Try it,
see if it answers your question.

(As always, since this is a sci.* newsgroup, please feel free to
falsify my math.)


Clear skies!

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------------------- Richard Callwood III --------------------
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