Why is the Moon so small?
Whatever its size, your computer monitor covers a much smaller part of
your field of vision than the sky (look straight up out in the country and you can't see anything
but sky.) But within the limitation of your monitor's restricted field, we have tried to give you,
by default, an impression of the amount of sky that your eye can take in. The result is that at
zoom = 1.0, objects are smaller on the monitor than they appear to the naked eye.
We have included in the zoom pop-up menu the value 3.5. This has been calculated to give roughly
the correct size appearance of objects, assuming that your eye is about twice as far from the
screen as the screen's width. So to see the Moon the "right" size, choose zoom = 3.5.
If your display area is 1 ft. across, and you are sitting 2 ft away, the horizontal angle of view
you can see is 16 degrees. This is equivalent to the RedShift zoom value of 3.5 (assuming the Sky
window is maximized).
Here are some other RedShift zoom values, together with the horizontal angle of sky displayed on
screen, and the equivalent 35mm camera lens focal length.
| RS zoom setting |
horizontal angle displayed on screen |
equivalent focal length (mm) for a 35mm format camera |
| 1 |
59 |
32 |
| 3.5 |
16 |
128 |
| 10 |
5 |
410 |
| 50 |
1 |
2000 |
Smaller RedShift zoom settings are not comparable to camera lenses because of RedShift's stereographic projection.
What can I do to make RedShift
run faster?
A number of RedShift 3's new features are processor intensive.
This does not mean that you can't get reasonable performance if you don't have a high
specification machine. The minimum requirement specified is a 100MHz Pentium processor with
16MB RAM, but RedShift 3 will run on 486 processor machines. But you should try to avoid
activities and settings which use a lot of processor power and memory.
If you would like to see a complicated scene in smooth animation, try making a movie. Whilst
making the movie may take a long time (you can always leave it recording whilst you do
something else), playback will be much faster.
The following is a list of things which consume significant power that you might want to avoid,
or to turn off.
The preview window in the Filters dialog
Each time you open the Filter dialog, or change a setting in a filter, RedShift refreshes the
preview window. Some users may find this annoying, especially with a slower machine. Un-check
the Show preview checkbox to stop this happening. If you want to take a quick preview, click
the checkbox on then off.
Planet images
By default, RedShift shows rendered images of the planets and in the case of the Earth, Moon,
Mars and Venus, you can go very close up and see a lot of detail. This requires RedShift to
load and process a lot of image data. At the same time, RedShift is calculating and drawing
the dark phase of the body (the side away from the Sun), and shadows cast on it by any
neighboring body (e.g. the moons of Jupiter casting shadows on its surface, or the same moons
being eclipsed by Jupiter) and the rings of Saturn. There are a number of steps you can take
if you want the display of planets and moons to go faster:
move further away (the smaller the size of the planet on screen, the faster the calculations)
for map views, move closer! Strange as it may seem, but you will get quicker responses when
very close to one of the mapped bodies the closer to the body you get
turn off phase (in the Filter dialog) for planets and/or moons
use a smaller screen resolution (see next topic)
show planets/moons as discs (this is a last resort, but may be useful in some circumstances)
High screen resolution
The higher the screen resolution you use, the more processing power is required for things such
as planetary images. Star and other catalog calculations, however, are unaffected.
When RedShift starts up, it takes note of the screen resolution that you have set. It then
arranges its own internal resolution so that when the Sky window is maximized, at zoom = 1.0,
59 degrees of sky are displayed. This also applies if you switch resolution whilst RedShift
is running. So if you switch to a lower resolution, you will get the same views, but fewer
pixels are used. This will speed up the display of graphical images such as the display of
planets.
24 bit color also requires more memory that 16 bit, and this will also make RedShift slower.
RedShift is optimized for 16 bit color.
The full Hipparcos and Tycho star catalog
By default, RedShift is set to display a restricted set of stars, and limiting magnitude is set
to 5.2 at zoom = 1.0. This should mean that star calculations are not significant at any zoom
level. But you may wish to see more stars on screen.
The complete Tycho and Hipparcos catalogs contain roughly one million stars. It is possible to
display a very large section of the sky in RedShift 3. If the filters are set with limiting
magnitude >13, and with all stars to be displayed, RedShift will display around 750,000 stars
at zoom = 0.26. It will also label them all, should you ask it to. Clearly such a display would
be useless, but there are many circumstances in which the display of a lot of stars is useful.
If you need to do this, then be prepared for longish calculation times.
All the asteroids
RedShift contains 7,369 asteroids. If you ask for all of these to be displayed, it must perform
orbital calculations for each of them - even if they turn out not to be visible from you location.
Each calculation is similar (although somewhat less detailed) to the calculation for the position
of a planet (there are nine of them) so it isn't surprising that this takes a lot of processor time.
If you are looking for a specific asteroid, use the Show selected asteroid feature. This also has
the benefit of applying a more accurate orbital model to the calculations (even if you don't
choose to use the precise orbits feature).
If you would like to see all the asteroids in a solar system view, use the asteroids filter to
limit the range of sizes displayed, until you have got your view set up. The, if you wish,
turn more on to see their positions.
Constellation images as graphics
It is possible to display all the constellations bitmap images at the same time. This will
take up a lot of processing time and memory.
Long time steps with precise orbits turned on
The precise orbits feature uses a special technique for calculating a body's position. Knowing
the body's motion at one particular moment (its speed and direction in space), RedShift uses a
sophisticated model to calculate where it will be instant by instant after that, taking into
account all the forces acting on it (such as the gravity of planets and the Sun, the solar wind
and atmospheric drag). If you make a large change to the date whilst the precise orbits calculator
is active for a body, the RedShift will calculate the entire trajectory of the body from the
previous date to the new one. Be prepared for a long wait.
Why can't I see the object that I am
aiming at?
The most obvious thing to check is the Filter for the class of object that you are trying to see.
Make sure that the object class (stars, planets, comets, etc) that you are trying to look at is
turned on. Note, for example, that by default not all of Jupiter's moons are displayed.
If the object is not a common one, or not a very bright one, make sure that you change the filter
sliders and checkboxes to show the whole range of objects.
If the object is not bright, make sure that either you are zoomed in sufficiently, or that the
limiting magnitude it set to a sufficiently big number to display the desired object.
See [filter dialog]
Why can't I see more stars?
By default, RedShift is set to display a restricted set of stars, and limiting magnitude is set
to 5.2 at zoom = 1.0. As you zoom in, more stars will be displayed, but not the full range in
RedShift's catalog. If you would like to see all the stars (especially if you have a fast machine),
use the stars filter to display the Tycho and Hipparcos catalogs and open the magnitude slider to
display the range -2 to 13.
My screen is completely black (or
filled with one color, or blocks of color), what happened?
There are several possible causes of this. To get out of it, perhaps the simplest thing to do is
to click undo to revert to your previous step, or to open default settings. The following may
provide the explanation.
You have a high zoom factor and there is nothing in the sky where you zoomed in (see also - why
can't I see more stars?)
You have a high zoom factor, and you are looking at the surface of a planet or moon
You don't have a high zoom factor, but you have gone behind a planet and you are looking at its
dark side
You are on the surface of a planet and are looking at an object that is below the horizon, or are
simply looking below the horizon (in which case you will just see the solid horizon color for
that body). If you like, you can ask RedShift to make the horizon transparent or invisible - see
guide filter.
Something is different - how do I
get back to how it was?
Sometimes you may click a control by mistake, or a control may have an unexpected effect.
The first step to take is to click UNDO (Edit menu or press CTRL+Z, or the undo button on the
control panel header). You can take multiple steps back. Alternatively, you can open the
default settings from the File menu; this will revert to the conditions when you first start
RedShift.
How do I control how RedShift will
appear when I start it up?
There are a number of ways to customize RedShift. See Customizing RedShift
I did something and RedShift spent
ages doing calculations - what happened?
Please see What can I do to make RedShift run faster for list of things that take long
calculations.
When I link to other Internet sites
from the RedShift site, how can I switch to using my usual browser?
By default, RedShift takes you to other Internet sites from the RedShift site using its integrated
browser. You may, however, wish to use the features of you usual browser when visiting these
other sites. You can use any browser to do this.
Right click to mouse button on the link you would like to explore outside RedShift. Choose the
item Copy shortcut. Open your usual browser and paste the shortcut into the address window and
press enter.
Please note that whilst you can browse some of RedShift's books using you usual browser, not all
the functions will work.
I am at one of Jupiter's moons (or
a moon of any other planet), how do I find where Jupiter is?
Open the [Location panel] to its maximum extent. Set the Location mode to Track body. Click
the pop-up in the Lat/lon box, and choose Relative..., the Jupiter..., then Outward. This moves
you to a position on the far side of the moon from Jupiter, so Jupiter will now be behind the
moon.
You probably would like to see Jupiter, and the moon is probably hiding it, so open the [Control
panel] and select to control position (or press F5 on the keyboard). Take one step in any
direction (using the Control panel or keyboard arrows) and Jupiter should appear from behind
the moon.
I have heard the name of an astronomy
object, but I can't remember what it is. How do I find out more about it?
Open the [Find dialog], make sure that Find: All is selected and type the first few letters of
the name. If it is in RedShift, the full name should appear in the scrolling list. Scroll the
list a little more to make sure that there are not several entries with a similar name.
Now click List links, and choose a link. A good place to start to find out about something would
be its dictionary entry or the object's info box.
Where I live, I usually don't see
very many stars. How can I get RedShift to simulate the sky in my city?
I have the same problem myself. Use the limiting magnitude feature in the [Filter dialog] to
restrict the objects that RedShift displays. Because object visibility is a very complex matter,
we can't create an exact simulation, but you will find this helpful in creating an approximation
to your sky.
Check how many stars you can see in a specific direction and then adjust the limiting magnitude
slider to show the same number, or slightly more. Now point RedShift to another part of the sky.
When you look outside, these are the stars and other objects that you should be able to see.
Why can't I see the Magellanic
Clouds?
We chose to represent the Magellanic Clouds as part of the Milky Way, but their labels
and icons are from the Deep sky object catalog. So if you wish to see the Magellanic Clouds
as "images", turn on the Milky Way.
Can I switch screen
resolution?
Yes you can, and whilst RedShift is running if you wish. When RedShift starts up, it takes note
of the screen resolution that you have set. It then arranges its own internal resolution so
that when the Sky window is maximized, at zoom = 1.0, 59 degrees of sky are displayed. This
also applies if you switch resolution whilst RedShift is running. So if you switch to a lower
resolution, you will get the same views, but fewer pixels are used. This will speed up the
display of graphical images such as the display of planets.
But take care; if you switch color depth (from example from 16 bit color to 24 bit) QuickTime
movies and stills will not display correctly. To fix this, restart RedShift.
I would like to get a map view,
how do I do that?
If you are interested in viewing the surface maps of objects (such as planets and moons) in
greater detail, choose track surface mode. You may also wish to turn off phase in the control
panel so that all of the surface is evenly illuminated (this will also make the display faster).
Open the Location panel fully (click the re-size button in the top right of the panel) and then
choose Map from the height pop-up menu.
To move around the map, change your location (don't forget, you are hovering over the surface).
Use the {Observer sub-panel] or set the [Control panel] mode to Position or press F5 on the
keyboard. Then the keyboard arrow keys, or the Control panel buttons will move you around the
map.
Double clicking to re-center the display will eventually give you a limb view of the planet or
moon.
How do I get that Solar
System view?
When you are moving around the solar system, it can be difficult to visualize where you
are. It is useful to display the Ecliptic plane using the [Guides filter], ecliptic section.
when viewing the solar system in Heliocentric mode. This provides a frame of reference to
help you visualize your position. If you turn on Ecliptic axes, distances from the Sun will
also be shown.
You may also want to display planet orbits and labels [Planets filter].
I don't understand the location
modes
Following planets and moons around the solar system involves complex trajectories that can be
hard to understand. RedShift simulates several modes of motion ([Location modes]) to give you
interesting views.
To get a better understanding of these modes, choose Motion preview from the Control menu; an
illustration of your present location mode and aim will be shown. Try changing Location mode to
see the effect on the illustration.
Where are the missing Messier and NGC objects?
We have chosen to omit a number of Messier and NGC objects. Here are our reasons.
M24
This object is generally agreed to be a pseudo-cluster of stars seen located at RA 18hrs 17min,
Dec -18deg 29min. As such it is not a "true" deep sky object. It is not the same as NGC 6603, which
is a nearby open cluster.
M40
This is really a pair of stars, which can be seen at RA 12hrs 22min Dec +58deg 05min. Some writers
have referred to it as a double star; the Hipparcos measurements reveal the two stars to be more than
300 light years apart. They are
HD 238107 at 510 ly
HD 238108 at 190 ly
M102
This is generally held to be a duplication of M101. Others have suggested that it may be a data
recording error, and really to be NGC 5866. If that is right, then you can look up NGC 5866 instead.
NGC numbers
In a numbers of cases, two or more NGC/IC numbers are associated with the same object in Sky catalog
2000. We have included in RedShift 3 only the first mentioned number. The following NGC/IC numbers
have been omitted for this reason.
Galaxies
NGC 943
NGC 1410
NGC 4657
IC 4554
Bright nebulae
NGC 1555
NGC 1934, 1935, 1936
NGC 2081
NGC 2078, 2079, 2080
NGC 2175
NGC 2238, 2239, 2246
NGC 3579
IC 2948
NGC 6595
IC 1284
NGC 6727
IC 4955
NGC 7133
Planetary nebulae
NGC 651
NGC 2372
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