Re: [guide-user] Putting the observatory outside the solar system.?

Bill Gray Jun 18, 2015

Hmmm... if you mean "observing from another object in the solar system",
you can do this as Michael Mattiazo has described: right-click on the object,
then hit the '<' key. You can even get an "out-the-window" view from the
International Space Station or other Earth-orbiting object that way, or
"look back" from Voyager 1 or 2. And, of course, you can get a view
from dwarf planets such as Ceres, Vesta, Eris, etc.

Observing from far outside the solar system, for example from other
stars, doesn't work so well. You can try it, using the method Masaki
Kouda describes, except with a _much_ larger distance. For example:

Use Go To... Object Name (or hit Ctrl-B). Enter 'alp1 cen' to get
Alpha Centauri A centered. Go to level 4, for a 20-degree field of

Hit Ctrl-F5. Enter -277700. (The distance to Alpha Centauri A is
a bit more than 277700 AU, or about 4.3 light years.)

You'll now be close enough to the components to see them separated
by several degrees. Click on them, and the magnitudes will be about
-15.7 and -14.6.

Now go to level 3, hit Go To... Object Name again, and enter
Betelgeuse. Orion doesn't look all that different (not surprising;
four light-years isn't much compared to the distances to most of the
stars in Orion), but what's that even brighter star next to Betelgeuse?
A right-click reveals that it's Sirius, a little over a degree away.

At this point, though, you may start to see the frayed edges of
this capability (and the reason I didn't go further with it). If you
zoom in much, Sirius will disappear. The problem is that I designed
a nice display method for dealing with the sky as a "two-dimensional"
spherical surface, dividing the sky into tiled regions. As you get
this far from the sun, some stars are no longer in their original
tiles. At large fields of view, this is not so much of a problem;
at level 3, you can see the tile Sirius was in when we were back on
Earth, so Guide recognizes that it should display Sirius. Zoom in
a little, and you lose that... to truly support a "galactic-traveler"
mode, I'd have had to develop a different sort of sky display engine.
(I did, in fact, design such an engine -- it's not really that hard
to do -- but never actually wrote it. It would never compete well in
terms of speed with the existing 2D method.)

I chose Alpha Centauri as an example because Guide's display engine
holds up passably well at four light-years from the sun, as long as
you don't zoom in on other nearby stars. It breaks down horribly as
you go further out.

I should also mention that if you center on the Sun, you'll
find it in Cassiopeia, at mag 0.5. Zoom in to a field of view of
a few arcseconds, and you can see planets down below mag 20.
Zoom into the smallest possible field of view, one milliarcsecond,
and the earth (at magnitude 24.1) spans a few dozen pixels, looking
down on Antarctica.

-- Bill