--- Alan Gornik <[EMAIL PROTECTED]> wrote:
>
> 2) But is the following similar? If I look at Polar Projection with
> field width>270deg,
There's another sort of "projection" involved here (besides
polar/zenithal). It involves the same issues terrestrial mapmakers
deal with when trying to plot part of a round globe onto a flat map.
You can see these options under preferences>projections. At >270�
field width, "cartesian" is the only available projection. Named after
Rene des Cartes, the mathematician/philosopher who invented coordinate
grids (and, I pressume, where we get the word "Cartes/chart" from), it
shows RA/dec lines as a rectilinear grid.
>I get a flat representation of the sky (I'm not
> really sure how to interpret where I am looking from)
You're seeing it from earth, but with more than 180� of the sky
"unwrapped" onto a flat plane.
>with the
> ecliptic oscillating up and down around the center. The planets, sun
>
> and moon seem to appear in the left to right order I expect. So it
> seems I am seeing the view from earth (but from where on earth?)
The view is as from your location (whatever location you have set under
"observatory").
> of
> the current relative position of the planets, right? Not the orbits
> but the next best thing. This view is pretty cool too because
> animation reveals the retrograde motions.
Even better:
1)use polar projection
2)set the field width to 269
3)under prefernces>projections, make sure the 180�-270� setting is
"arc"
4)find Polaris and Vega
5)right-click on the point about half-way between these two stars (this
is the "ecliptic pole"
6)in the right-click menu, choose "center" to center the chart on this
point
7)animate
You'll see the sun, moon and planets all rotating around the center of
the chart.
For faster results, turn off catalogs, Milky Way shading, etc. Leave
the constellation outlines for reference.
> 3) Is there any way to determine max planetary elongations?
Check out S&T's "Skygazer's Almanac". It's a single chart that does a
good job of showing which planets are visible, max elongation,
oppositions, sun/moon rise/set times, etc. Not available online as far
as I know, but you can order it for $3, or $15 for poster size. If you
have a subscription, you get the smaller two-page size with each
January issue.
My favorite physics pun: after Galileo showed there was no preferred
reference frame for the universe, and Einstein went even further, that
left some of the more philosophical minded physicists wondering what
was more important: space itself, or the reference frame? Some said
the reference frame, but others countered, saying that that was a clear
case of putting des Cartes before des horse.
-John (ducking and running ;)
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