How to Read the ACLPPP Profile
PROFILE EXPLANATION (for ACLPPP profiles)
__________________________
PROFILE HEADING DATA The following information is found in the
heading:
LINES 1-2 These are the scale in Watts an-
gles. The values on the scale
are printed in one-degree inter-
vals from the Watts angle of
central graze.
LINE 3 This is the time from central
graze in one-minute intervals.
Vertical bars are generated for
each minute through the plot,
with the one for central graze
so labeled. Negative numbers
indicate minutes before central
graze, and positive numbers min-
utes after central graze.
PROFILE PLOT Horizontal bars are drawn across the plot
at regular intervals to help in scaling the
distance from the predicted limit. One of
the lines is the predicted limit, and is
labeled as "PREDICTED LIMIT" on the right
side, and "0" on the left side. The verti-
cal scale on the right side is the number
of miles or kilometers from the limit,
while the scale on the left side is seconds
of arc from the limit. A negative value is
south of the limit and a positive value is
north of the limit.
The actual profile data are a series of
letters, numbers, and asterisks that can
look busy and bewildering. Some observers
have found that drawing smooth curves
through the points for the limb and for the
predicted profile help in understanding the
plot. There are at least two curves re-
presented on each plot, and sometimes more.
Each plot has a curve for the smooth mean
limb of the Moon, and a more jagged plot
for the predicted profile. In addition,
the terminator may appear on the plot, if
it is near the central graze. If the star
is double, and both components will graze,
the profile for the secondary (and terti-
ary, if there is one) component will also
be provided.
The codes for the limbs and terminators
are:
D dark limb of the Moon
B bright limb of the Moon
T terminator
W "worst" terminator, where two-mile
(3-km) high lunar mountain peaks can be
sunlit. Areas enclosed by W's will usu-
ally be sunlit at the south limb, where
high mountains are common, and will usu-
ally be dark at the relatively smooth
north limb
The codes for the profile points are:
* good limb correction, typically accurate
to 0.15"
1 fair limb correction, accurate to 0.3"
2 meaningless limb correction, either ex-
treme librations or in the Cassini re-
gion (see "The Lunar Profile" on page
8).
3 good limb correction from previously ob-
served graze data, accurate to 0.4"
4 poor limb correction from previously ob-
served graze data, accurate to 1"; most
of the Cassini regions have been crudely
"mapped" with previously observed
grazes, so 3's and 4's usually dominate
the profile when a graze occurs in these
regions
5 good limb correction with an empirical
correction applied (* [or 0] + 5)
6 fair limb correction with an empirical
correction applied (1 + 5)
7 meaningless limb correction with an em-
pirical correction applied (2 + 5)
P shifted limb of the primary component of
a multiple star (when the star is not at
the position used for the limb predic-
tions, which is often the case when a
center-of-light, or mean position, is
used)
S shifted limb of the secondary component
of a multiple star
R shifted limb of the tertiary component
of a multiple star
When drawing curves through the plotted
points, the following groups should be con-
nected together. A different color pen for
each group makes the profile more readable.
B AND T enclose bright area of the Moon
D encloses dark mean limb
W encloses area where sunlit peaks
may exist and cause observing dif-
ficulties ("worst" terminator)
*,1-7 the predicted limb for mean star
position
P the predicted limb for a primary
star not at the mean star position
S the predicted limb for a secondary
component
R the predicted limb for a tertiary
component
At the bottom of the profile are seven
lines of additional information about the
profile and the star.
LINE 1 The date, UT hour and latitude
libration of the graze is given.
LINE 2 The star number in the ZC or X
catalog, the version of the USNO
profile prediction program that
generated the data for the plot,
and the longitude libration of
the graze are given.
LINE 3 This line gives the limit
(northern, southern) of the
graze and the vertical profile
correction (VPC) in seconds of
arc (north is positive).
LINE 4 The Watts angle of central graze
(for the point in the limit
closest to the observer), graze
height (of the predicted limit
from the mean limb in seconds of
arc, with positive values indi-
cating a shift away from the
center of the Moon), the cusp
angle, and the name of the per-
son running the profile program
are given.
LINE 5 The horizontal profile scale
(HPS) in minutes of time per
degree of Watts angle, the pos-
ition angle for the point in the
limit closest to the observer,
and the person for whom the pro-
file was produced are given.
LINE 6 The vertical profile scale (VPS)
in seconds of arc per mile or
per kilometer, the distance of
the observer to the limit line,
and the observer's home location
are given.
LINE 7 The empirical corrections ap-
plied are identified.
LINES 8-9 Additional information is given
if the star is multiple. The
type (double, triple), the dis-
tance of the primary from the
mean position, the magnitude,
separation, position angle, and
the vertical and horizontal
shift in the profile for each
component are listed. Vertical
shifts are given in miles (or
kilometers) and seconds of arc,
horizontal shifts in time. In-
formation is given for compo-
nents that do not show on the
plot.