"Mark Gingrich" wrote in message
...
Greg Neill asked:

A question on observing: What would be the minimum elongation
(angle betwixt a planet and the Sun) that would allow it to be
spotted by naked eye? We can assume the use of filters to save
our eyes.

Does it vary for different naked-eye planets?


From page 480 of _Explanatory Supplement to the Astronomical Almanac_,
P. Kenneth Seidelmann (Editor), 1992:

Visibility Criteria for Geocentric Phenomena

Body Minimum Elongation

Moon, Mars, Saturn 15 degrees
Minor planets 15 degrees
Venus, Jupiter 10 degrees
Mercury 10 degrees + visual magnitude of Mercury


[These numbers strike me as being suspiciously uniform and crudely
rounded. But then, they come from the same people who persist in
playing up a fictitious event for Venus called "greatest brilliancy."]

Interesting.
I have to agree with your observation on the numbers seeming to
be a tad contrived.

Paul Schlyter indicated that he's successfully spotted Venus
near superior conjunction within a degree of the Sun while
employing a 4" refractor.

Thanks for the reference.