St. Tammany farmer. [volume] (Covington, La.) 1874-current, 1894-03-03
HARVEST AND HUNTERS MOONS



Brief Stateusats - 20 the Causes o.
These Celestial Phs.Omsna.
The time Of moonrise on any day il
ON the average about fifty one minutes
later than il was on the preceding day.
This retardation h, however,, by NO
means constant In amount, being ~
times very much less. than the average
and at times very much greater. A
very marked diminution in the time OF
retardation occurs about the time OF
the full moon which falls in Septem-
Der. This moon is called the harvest
moon. The same phenomenon. IN .
less degree, occurs at the time OF the
next following full moon. which 10
known as the hunters moon The
time OF retardation during the harvest
moon is less than half an hour In our
latitudes. instead of its average value
of nearly an hour, and for several sue
cessive nights the moon seems TO rise
at nearly the same time.
Briefly stated the cause of the phs-
nomenon is this: At the time OF the
rising of tho harvest moon the appar-
ent path of the moon among the stars
is much less inclined to the horizon
than it is at other times. and the ordi-
nary days motion of tho moon along
this path makes an unusually small
change Of position of the moon with
reference to its distance from the
horizon.
A more detailed explanation may
make the matter a little more easily
understood In addition to tho ordi-
nary apparent daily motion which the
moon has in common with all other
heavenly bodies, it has another motion
by which it. completes the circuit OF
the heavens relatively to the sun once
a month, and the direction Of this mo-
tion IL generally net PARALLEL with the
direction Of the diurnal notion. it be-
ing generally northward or south
ward as well as eastward. Anyone
may see the motion by an hours
watching Of the relative positions OF
the moon and . star near 1t.
The diurnal motion is always On
a line at right angles to q
line drawn from the body to the
celestial pole, the point in the heavens
approximately indicated by the pole
star 1t is always perfectly uniform
bout the pole as q center. and 1t IS
this which we take as our ordinary
measure of time.
Now consider the position Of tho
moon and the sun at the time of full
moon. The moon rises just as the sun
sets. On the next evening at sunset
the moon will still be below the hori-
| ZOE, because it has moved eastward
among the stars relatively to the sun.
and il will not rise until the diurnal
motion of the heavens brings It above
the horizon. II the moons motion were
uniform and always along the line OF
ordinary diurnal motion. this retaraa-
tion of the time of rising would always
be the same. and would, as stated at
the outset, be fifty-One minutes per
day. But at the time of harvest moon
the direction of motion Of the moon
among the stars is considerably north
ward as well as eastward, and
at the time of moonrise this line
] makes . comparatively small angle
with the horizon, very much less than
IL does at other times of full moon
Fdurin4 the year. Therefore, st sunset
On the day after the full, the moon
Having moved along . line which is IN
clined to the horizon at q much smaller
tangle than usual. its distance below
the horizon will be less than the aver
age, and hence . smsller amount of
diurnal motion will bring it into view
that is the retardation of time Of
rising is less than il is at other times.
This condition continues for several
days
Several other things. notably the in
clination of the moons orbit to that
of tho earth. and the varying rate Of
motion in the orbit due to variation Of
distance from the earth, tend to change
the amount Of daily retardation, but
they do not depend on the time Of the
year, and they sometimes intensity
and sometimes diminish the peculiar
phenomenon of harvest moon. Lsti-
tude has strong effect, and in north
crn Europe the phenomenon is much
more noticeable one than it is in the
United States. In fact if one goes far
enough north. the harvest moon may
rise even earlier on any night than il
did on the night preceding. Popular
; Science News