--- Alan Gornik <[EMAIL PROTECTED]> wrote:
>
> I am really enjoying getting to know this program (and thus our
> Universe) better! I am brand new to astronomy, so I hope these are
> not too basic.
>
> 1) Why would one use the rotation +-15deg arrows? It just seems to
> mess things up after you do.
When looking through a scope, after the light bounces off various
mirrors and exits the scope at some arbitrary angle (when using a
diagonal, or in a Newtonian, where the focuser drawtube can be at
random angles), the view through the eyepiece is likely to be at an odd
angle. So the ability to see the chart at different angles can help to
match the view with the chart, to help figure out what you're looking
at.
The arrows allow you to rotate the chart in 15� increments. You can
set an arbitrary angle with the "orientation" setting in Search>Locate
New Position. The double arrows in the middle of the left toolbar flip
the chart, which is useful if your scope shows a mirror-reversed image,
which is common.
> 2)If I click Show all sky & Zenith then Polaris appears near the
> top. But then when I click Polar Projection & Show all Sky, Polaris
> is no longer at the top? Why not? What causes the chart to move?
When you click Show all Sky, the program automatically switches to
zenithal projection, where normally the zenith is "up". But in this
case, the zenith is at the center, in order to show the whole sky.
Whatever you had centered in the previous chart will be below center,
so it's as if you were looking at the area of previous chart in "real
life", and then raised your head to see the whole sky.
When you press "zenith", that normally puts the zenith in the middle of
the chart (it already is, in this case). But since "Show all Sky"
causes the program to switch to zenithal projection, it wants to have
the zenith be the "up" direction in the chart. But that's impossible
if the zenith in the center. So it uses the next best choice, which is
to use north as "up". So Polaris ends up at top.
In the second case, whether you use polar or zenithal projection, when
you click Show all Sky, the center of the previous chart will be below
center.
> 3)In the Search>Locate New Position, what is that position on a
> chart?
The center.
> If I change a variable, how do I see that reflected on a chart?
After editing the numbers, just click "ok", and the chart should change
to the new position, width, and orientation.
-John
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