Quasars,  or QSOs,  or "quasi-stellar objects",  look,
as the name implies,  a lot like stars.  A closer look
shows that they are extremely far away (the most distant
observable objects in the sky).  In order to be so bright,
but so far away,  they have to produce enormous amounts of
energy.  They can also be observed to be very small,  and
the leading theory as to what can make an object so small
produce so much energy assumes a black hole in the
center of a galaxy.  The black hole sucks in surrounding
gas and stars,  which form a tremendous accretion disk,
which produces immense amounts of energy in the form of
heat (infrared radiation),  light,  X-rays, and gamma
rays,  as the matter falls in.
   Some of these objects vary in brightness and were
labelled as variable stars by mistake,  such as BL Lac.

Quick Info 
   The Quick Info option in the Help menu provides a list of
such data as current planet positions,  bright comets and
asteroids,  sidereal times,  the visual magnitude limit and
field rotation rate at the chart center,  calendar data,  and so
forth.  It can be reached with the Alt-Q hotkey.

R CrB 
   R CrB stars are named,  logically enough,  after the
variable star R CrB.  This star is usually visible at
about magnitude 6,  just barely invisible to the unaided
eye.  Every now and then,  it will suddenly drop to about
magnitude 14,  then recover to mag 6 again.

RA second 
   The usual unit for measuring very small angles is the
arcsecond.  Angles measured in arcseconds are denoted
with the " (double quote) symbol,  as in,  "The object was
34" across."
   Unfortunately,  from time to time,  another unit,  the
RA second,  is used.  One RA second is the angle through
which the earth turns in one second,  just as an RA minute
is the angle through which the earth turns in one minute
and an RA hour is the angle through which the earth turns
in one hour.  Guide mostly avoids the use of RA seconds,
and will usually multiply such values by 15 and display
them as arcseconds.  In a few cases,  however,  a source
catalog will provide data in RA seconds and Guide will
follow suit.

RA/dec format 
   The RA/dec format dialog option in the Settings menu provides
a way to choose how RA and declination values are shown in Guide.
By default,  they are always shown in the J2000 equinox and with
decimal seconds.  But coordinates are often given by some sources in
decimal minutes or degrees,  or in the B1950 epoch.
   The format you choose in this dialog will be used in displaying
coordinates throughout Guide.  But you can always enter coordinates
in any format you choose;  Guide will figure out the format and will
still understand your entry,  even if its format does not match that
chosen in this dialog.
   Also,  this dialog box provides options to set the formats used in
showing latitude/longitude values,  and to toggle between metric
and English units.

Radial and/or Rotational Velocity 
radial velocity 
rotational velocity 
   If you examine an object's spectrum,  you will often
see that the star is redder or bluer than you would
expect. This is caused by the Doppler shift:  the object
is moving toward or away from the Earth.  By measuring the
amount of shift,  you can find the object's velocity.
Notice that this only tells you the speed of approach or
receding;  the object could be moving sideways at any
speed and the spectrum wouldn't show it (though proper
motion studies might). This speed is therefore called a
radial velocity.
   Also,  you may see that a given spectral line is
"blurry".  If an object spins quickly,  the spectrum of
the side approaching you will be bluer than usual;  that
going away will be redder than usual,  once again because
of Doppler shift,  and once again,  measuring the blurring
tells you how fast the object spins.  Unfortunately it
only tells you the spin speed relative to Earth:  an
object could have a lot of spin most of which is sideways
to us (i.e.,  its axis is pointed at us,  or nearly so),
and we would never know.

Radial galaxy velocity 
   According to present thinking,  there is a direct
linear relationship between how fast a galaxy moves
away from us and how far away it is;  i.e.,  the faster
it moves away,  the farther away it is.
   The problem is that the exact relationship is not all
that well known.  We can measure the speed at which a
galaxy recedes with some precision,  using the Doppler
shift.  Measuring how far away galaxies are requires the
use of much less precise techniques.  This program will
only give the radial velocity (if it's been measured for
the galaxy in question).  The corresponding distance
depends on the "Hubble constant",  the value of which has
been a matter of intense debate for many decades..

   The meteors from a meteor shower generally appear to
"radiate" from one point in the sky.  That point is called
the radiant,  and usually provides the name of the
shower;  for example,  the radiant of the Perseids is in

Radius or Diameter 
   Most stars appear as pinpoints in any instrument we
have available today.  A few of the larger and closer
stars have apparent angular diameters that can be
measured.  Knowing this and a star's distance can tell
you how big it really is.

Rapid irregular 
  The rapid irregular type of variable star will change in
brightness by about .5 to one magnitude for a few hours or
days.  They are a lot like Orion type variables,  and in
fact,  the boundary between the two is blurry.  The main
feature of the rapid irregular variables is that they are
not in a nebula (and therefore must have a different
reason for varying than Orion type variables do).  It
takes some care to make sure these objects are really
irregular,  and not some periodic or BL Lac object.

Rapid-change Orion type 
   A rapid-change Orion type is simply an Orion type
variable that has been observed to change brightness very
rapidly,  by about one magnitude in one to ten days.

Rapidly oscillating Alpha CVn 
   Rapidly oscillating Alpha CVn stars are variable stars
with strong magnetic fields,  with strong,  nonradial
oscillations (basically,  they quiver like Jello).  The
variations take place on a time scale of a few minutes,
and are small (about .01 magnitude).  In addition,  they
show the sort of variations found in normal Alpha CVn

   The Variable Star Section, Royal Astronomical Society of New Zealand
(VSS RASNZ) gathers and distributes data regarding variable stars;
especially those in the southern skies.  The VSS RASNZ has members
throughout the southern hemisphere and low northern latitudes.

   Most southern variables are poorly observed - if at all - and the VSS
RASNZ welcomes observations from amateur (and professional) astronomers.

For further information, contact:
PO Box 3093
Greerton, Tauranga

Tel. / Fax  +64 7 541 0216
Internet:  varstar@voyager.co.nz

Third Reference Catalog 
   The RC3 (Third Reference Catalog) contains information
on over 23,000 galaxies.  Should you click on a galaxy in
this catalog,  information from the RC3 as to the object
position,  size,  etc.  will be provided when you "click
for more info".
   The RC3 was compiled by G. and A. de Vaucouleurs,  H.
G. Corwin,  R. J. Buta,  G. Paturel,  and P. Fouque.

Reference: Rodgers, A.W., Campbell, C.T. and Whiteoak, J.B.: 1960,
Monthly Notices Roy.Astron.Soc. 1221,103. A catalogue of
H-alpha emission regions in the Southern Milky Way.

   This menu item causes animation to run in "real
time.",  i.e.,  planets and asteroids are shown in
their current location,  based on the time provided by
the computer's built-in clock.  Also,  the altitude
and azimuth shown for clicked-on objects is updated
to match the actual alt/az for that object.

RealSky image 
   If you have the eight-CD set of RealSky images from the
Astronomical Society of the Pacific,  you can extract images
from those CDs and have them displayed in the background of
Guide's charts.
   To do this,  center the chart on the object of interest,
and click on the RealSky image in the Extras menu.
Guide will ask for the size of the image to extract,  in
arcminutes.  You can just enter,  for example,  "20" for
a 20x20 arcminute region;  or "20x30" for a region 20'
wide and 30' high.
   Guide will then start up a separate process to extract the
image.  You'll be asked to insert a RealSky CD and hit
Enter.  (You may need to do this twice on some systems
before the CD is properly recognized.)  The process will
give you a "percent completed" progress report,  and will
then ask you to re-insert the Guide CD-ROM.  Do so,  and
hit Enter (again,  a repetition may be necessary).
   Control will be returned to Guide,  and the image will
be shown,  correctly oriented on the chart.  You can zoom
in and out on it,  and print it if desired.
   You can also access this option with the Alt-F6 hotkey.
   There is also an option available to clear RealSky
images when desired.

   If an object is moving away from us,  we see a shifting
of its light toward longer wavelengths.  This is an
example of Doppler shift.  It can be measured to give
a velocity,  expressed either in kilometers/second or
in terms of the speed of light.  The figure is the
object's redshift.

Reflecting binary 
   A reflecting binary variable is a type of variable star
where light from the hotter star is reflected from the
cooler star.  So when the hotter star is closer to us,
the amount of light from the pair is raised.  Since the
stars have to be close together for this effect to be
really noticeable,  they may eclipse one another as well.
Usually,  the range of brightness variation is .5 to 1
magnitude.  An example of this class is KV Vel.

reflection nebula 
   A reflection nebula happens when a nebula is lit up by
a star on the inside.  Light from the star is reflected
by gas in the nebula.  This is different from an emission
nebula,  which gets heated up by a star on the inside to
the point where it glows on its own.

   Refraction refers to the bending of light as it passes
through different media.  The bending as it passes from,  for
example,  air through water is quite obvious; the bending as
it passes from vacuum to air,  or between different densities
of air,  is not as obvious.  The effect of refraction is to
make objects appear higher in the sky than they otherwise
would.  Objects more than halfway from the horizon to the
zenith (i.e.,  with an altitude greater than 45
degrees) are almost totally unaffected. Objects near the
horizon can be shifted by a degree or so. The shift is not
always the same from one part of the sky to another;  this is
why the rising and setting sun often looks distorted,  and
why mirages can occur at some times but not others.
   A further complication is that air masses move continuously,
creating complex and unpredictable refractive effects.  That
causes the continous moving and deformation of telescopic
images known as seeing.
   Guide computes refraction using the temperature and pressure
data you supply in the Location dialog.  Despite this,  the
actual observed refraction can vary by several arcseconds from
the computed refraction.

repeating nova 
   A repeating nova is much like a garden-variety nova,
except that the explosions will repeat after a few
decades.  A good example is T Pyx.  Normally,  this star
stays at about magnitude 14.  In 1890,  1902,  1920,
1944,  1967,  and 1997,  it suddenly leapt up to about
magnitude 6 or 7.  It then stays bright for a while,
dropping back over months.

Republican calendar 
   The French Republican Calendar was established in 1793 and abolished
in 1806;  it's only of historical interest now,  and was apparently never
used outside of France.  But it does shed light on the idealistic
psychology of the Republic;  it reflects a true optimistic belief that a
new age of reason was dawning.

   Under the Republic,  almost everything "old" and "irrational" was to
be replaced by new,  rational thinking.  Feet, inches,  and pounds were
thrown out to make way for the metric system;  the clumsy units of
hours,  minutes, and seconds were replaced with decimal versions;  and a
new calendar, with twelve months of 30 days each,  was introduced.  The
months were:

Vend‚miaire (Vintage) = 22 Sep to 21 Oct (roughly)
Brumaire (Mist) = 22 Oct to 20 Nov
Frimaire (Frost) = 21 Nov to 20 Dec
Niv“se (Snow) = 21 Dec to 19 Jan
Pluvi“se (Rain) = 20 Jan to 18 Feb
Vent“se (Wind) = 19 Feb to 20 Mar
Germinal (Seed-time) = 21 Mar to 19 Apr
Flor‚al (Blossom) = 20 Apr to 19 May
Prairial (Meadow) = 20 May to 18 Jun
Messidor (Harvest) = 19 Jun to 18 Jul
Thermidor (Heat) = 19 Jul to 17 Aug
Fructidor (Fruit) = 18 Aug to 16 Sep

   The archaic,  illogical,  meaningless month names of the old calendar
were replaced with logical,  meaningful names.  Months such as "July"
and "August",  named after utterly undemocratic Roman emperors, were
discarded.  The month names within each season rhyme,  probably as an
aid in remembering them.

   This does leave five "extra" days at the end of each year (six days,
in leap years).  These were given the following names:

Jour de la vertu (Virtue Day)
Jour du genie (Genius Day)
Jour du travail (Labour Day)
Jour de l'opinion (Reason Day)
Jour des recompenses (Rewards Day)
Jour de la revolution (Revolution Day)   (leap years only)

   The first day of the calendar,  1 Vend‚miaire 1,  corresponds to
Gregorian 22 September 1793 (keeping in mind the Republican Calendar
wasn't actually established legally until 5 October 1793).

   The thirty days of each month were organized into three weeks of ten
days each.  The Republican leaders were in part trying to evade the
religious aspects of a seven-day week,  and presumably also liked
having a "decimal" week.  Unfortunately,  providing one day of rest every
tenth day,  instead of one every seven days,  was not a popular move.

   Leap years are those divisible by four,  except for those
divisible by 128.  This slight deviation from the Gregorian scheme,
in which leap years are those divisible by four,  unless divisible by
100,  unless divisible by 400,  is slightly simpler and gives a
calendar that is _much_ closer to the true tropical year.

   Unfortunately,  when first devised,  the French attempted to have
New Years Day line up with the autumn equinox,  which is not
particularly regular and was probably a real pain in a world without
pocket calculators.  Thus, between 1 AR and 20 AR,  leap years
occurred a year early;  i.e, years 3, 7, 11,  and 15 AR were leap
years;  after that,  they were supposed to revert to the rule
described above.

   There are also claims that leap years were to follow the Gregorian
"4, 100, 400" rule.  I have no real evidence to support one scheme over
the other.  But I suspect that a revolution so devoted to revising
every aspect of human existence that it changed names of all months,
"regularized" each to be 30 days,  and made a week ten days long,
probably went out of its way not to produce a calendar resembling that
proposed by a medieval,  pre-scientific Pope.  Also,  the fact that it
would be an almost perfect match to the tropical year would lend
support to the scheme.  In any case,  the irony of the Republic
creating a calendar that would be good for a hundred thousand years
is interesting,  considering that the Republican calendar was abolished
in Year 14.

   If you viewed the solar system from well above the north pole of
the Sun,  you would see that almost all objects orbit the Sun in
a counterclockwise direction;  almost all rotate around their axes
in a counterclockwise direction;  and almost all satellites orbit
their planets in a counterclockwise direction.  This is called
prograde,  or "forward",  motion.
   However,  there are exceptions to all this.  Some comets
orbit the sun in a clockwise direction.  Venus and Uranus
rotate clockwise around their axes.  Triton,  the largest
satellite of Neptune,  orbits in this reversed direction;
and so do some other,  small satellites of outer planets.
This is called retrograde,  or "backward",  motion.

rise/set times 
   When you click on an object,  this program calculates
the times of rising and setting,  as seen from the place
on the earth (latitude/longitude) chosen in the Settings
menu.  They assume "average" refraction.  For the sun and
moon,  "rising" occurs when the top of the object appears
above the horizon,  "setting" when the top vanishes below
the horizon.
   Changing atmospheric conditions at the horizon (which
is,  after all,  where objects rise and set) make it not
possible to determine rising and setting times with more
accuracy than a minute or two.  Under unusual conditions,
the accuracy may be still worse.
   Unless you are at the equator,  there will be some
objects that never rise and set,  and are either always
above or below the horizon.  For example,  those of us
in the United States never can see the Southern Cross or
the Magellanic Clouds,  but we can always see the Pole
Star and the Little Dipper (Ursa Minor).  Objects that
are always visible are called circumpolar.

rotation period 
   An object's rotation period is the time it takes it
to turn once on its axis.  For the Earth,  the rotation
period is one day.  For the Sun,  it is about a month;
for the Moon, 27.5 days.
   Some asteroids have had their rotation periods
measured.  This is done by measuring the brightness of
the asteroid over time.  If the object is not very
round (which happens frequently with small asteroids),
or if it has bright and dull markings,  the brightness
will go up and down as the asteroid turns.  The time it
takes to go up,  down,  and up again will usually equal
the rotation period.

   The RR CrB type of variable star is not very different
from the Z Andromedae type.  This type is also an older,
cooler star,  but its variations in light are not as
regular and it takes more observations to determine it.
Often,  there are two periods of variation superimposed on
each other,  sometimes reinforcing,  sometimes cancelling
each other out.

RR Lyrae 
   The RR Lyrae type of variable star is a radially
pulsing star of spectral type A to F (hotter than the
Sun),  varying by .2 to 2 magnitudes in brightness.  They
are found,  sometimes in great numbers, in globular
clusters.  They always have the same intrinsic luminosity,
which means that if you spot some in a globular cluster,
you can tell how far away that cluster is.  They have
short periods,  of a day or less in length.

RR Lyrae with two pulsation modes 
   This type of RR Lyrae star is a variable with two
cycless of pulsation,  sometimes coinciding,  sometimes
cancelling one another out.  An example is AQ Leo.  The
ratio of the lengths of the cycles is about .745.

   The RS CVn type of variable is a close binary pair of
stars with unusual amounts of activity in their atmospheres,
causing pseudo-periodic variations in light.  The period
of light variation is close to the orbital period.  The
amount of variation is usually as great as .2 magnitude.
They are also X-ray sources and rotating variables (as
they rotate,  different parts of their surfaces with
different intensities become visible.)

RV Tau w/long-term variation 
   Many RV Tauri stars have,  on top of the light changes
normal to that class of variable star,  a tendency to
vary in brightness by up to 2 magnitudes over a period
of 600 to 1500 days (2 to 5 years).

RV Tauri 
   RV Tauri type variable stars are supergiant stars that
regularly swell and shrink.  Both the brightness and
spectral type vary:  at their brightest,  they are of type
F or G (like the Sun or a little hotter);  at dimmest,
type K or M (cooler than the Sun).  The minimum magnitude
alternates between two values from one cycle to the next;
the level of these values also varies over time,  so that
sometimes the dimmer minimum will swap places with the
not-so-dim minimum value.  The light curve (graph of time
running horizontally versus brightness running vertically)
looks like this:

with a deep minimum followed by a shallow one,  and so on.

@m   0,200     Maximum
@l  10,200
@l  20,210
@l  30,230
@l  40,260
@l  50,270     Deep minimum
@l  60,260
@l  70,230
@l  80,210
@l  90,200     2nd max
@l 100,200
@l 110,210
@l 120,230
@l 130,250
@l 140,260     Shallow minimum
@l 150,250
@l 160,230
@l 170,210
@l 180,200     3rd max
@l 190,200
@l 200,210
@l 210,230
@l 220,260
@l 230,270     Deep min
@l 240,260
@l 250,230
@l 260,210
@l 270,200     4th max
@l 280,200
@l 290,210
@l 300,230
@l 310,250
@l 320,260     Shallow minimum
@l 330,250
@l 340,230
@l 350,210
@l 360,200     3rd max
@l 370,200
@l 380,210
@l 390,230
@l 400,260
@l 410,270     Deep min
@l 420,260
@l 430,230