Re: Planet X: Viewing WHEN?
I M Openmind wrote in message <email@example.com>
> Jeff wrote in message <firstname.lastname@example.org>
>> Good question, though I figure you made a typing mistake when you say
>> the sun rises at 4:13 am, especially if you get up at 4:30 and you do
>> NOT see the sun! :) It's currently rising around 5:17am for your area.
>> As for darkness, you START losing that at around 2:59am, or basically
>> 3:00am. So after 3am, you skies will start getting brighter. If your
>> mythical Planet X did exist, it would not be visible (unless it's as
>> bright as Venus or something) since it would rise at around 4:38am.
>> And I wouldn't use M31 as a comparison since it is very large and
>> has it's brightness spread out over a large area. If you can provide
>> the angular size and magnitude of your mythical object, I'm sure there
>> are some out here that could calculate when such an object would
>> be visible for your area.
> It is true that astronomical dawn (sun 18 degrees down) currently
> begins for Nancy at about 3AM. That is, however, a fairly technical
> definition of dawn which is detectable only with precision measurement
> (it is when the contribution to the sky background by scattered
> sunlight is equal to the contribution from the natural sky
> background). I have chosen to use nautical dawn (sun 12 degrees down)
> as my cutoff time simply because that is when the horizon just becomes
> visible because of the sky brightness. Most naked eye stars are still
> visible to the naked eye observer at this time and with a telescope
> all but the faintest telescopic objects will be visible with a small
> It is fun to note that this whole topic resulted originally from my
> post showing that in fact Nancy's position could be visible (albeit
> barely) in "mid-year 2002" as she had said when some were posting that
> she was (as usual) all wrong. It is particularly fun to see Nancy, in
> her effort to show me wrong, avocating the position that she (and her
> source) was wrong in the oft repeated mid-year 2002 visibilty
As a side note, if you insist on astronomical dawn as the cutoff, then
for Capetown SA, the window (Nancy 15 degrees up, sun 18 degrees down)
begins July 1. For Madison WI the window is delayed much more, until
the last few days of July. So Nancy was "correct" that her
coordinates would be viewable in mid-2002 and hence she and her
sources are wrong when they now argue that viewing must wait until
later. Isn't it likely that she is trying to delay the time when
folks start asking "where is it"?