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or else you may note the altitude as you find it first by by the
place of the crosse at first; & after set downe so much as a in degrees
or minutes as it is from the place of the crosse answereth to the qua quantity
of the excentricity, which hereafter is called the parallaxis of the staffe;
to remayne to be abated with some other things as shalbe taught
place of the crosse at first; & after set downe so much as a in degrees
or minutes as it is from the place of the crosse answereth to the qua quantity
of the excentricity, which hereafter is called the parallaxis of the staffe;
to remayne to be abated with some other things as shalbe taught
If to the prime end of the staffe that is to say the end which is next the
eye nere ioyned a peece of wood of the length of the excentricity the use
wold now be somewhat reddier for your owne ey without removing the crosse
any otherwise then in the observation, or further consideration of the staffes
eye nere ioyned a peece of wood of the length of the excentricity the use
wold now be somewhat reddier for your owne ey without removing the crosse
any otherwise then in the observation, or further consideration of the staffes
There is yet an other thing to be noted in observing of altitude by the
staffe. The seamen use comonly to leave the horison open the observation observing,
which in deed were good if they know how much, but because of the uncertayne
coniecture they may make greater greater error then is fit to be permitted.
They have the practice by tradition from one to the other. The reason thereof they
told none in there writings, nether being demanded to they answere
any otherwise then that not doing so, the altitude wold not be true, nor
agree with the Astrolabe. Which without doubt have ben found by comparing
the staffe & the Astrolabe to
staffe. The seamen use comonly to leave the horison open the observation observing,
which in deed were good if they know how much, but because of the uncertayne
coniecture they may make greater greater error then is fit to be permitted.
They have the practice by tradition from one to the other. The reason thereof they
told none in there writings, nether being demanded to they answere
any otherwise then that not doing so, the altitude wold not be true, nor
agree with the Astrolabe. Which without doubt have ben found by comparing
the staffe & the Astrolabe to
By truth of demonstration which I have uttered in my Arcticon, which
here for brevity sake I omit. I have proved that the ey being above the
levell of the water at sea, doth see more then half the heavens. And therefore
from the zenith or highest poynt above our heads to the apparent horizon is
more then 90 degrees. And that surplus is the greater, according as the
ey is above the levell of the water. And therefore any high that is
taken by the staffe close, because it hath respecte to the visible horizon, is
greater then from the true horizon of the
here for brevity sake I omit. I have proved that the ey being above the
levell of the water at sea, doth see more then half the heavens. And therefore
from the zenith or highest poynt above our heads to the apparent horizon is
more then 90 degrees. And that surplus is the greater, according as the
ey is above the levell of the water. And therefore any high that is
taken by the staffe close, because it hath respecte to the visible horizon, is
greater then from the true horizon of the
Yet notwithstanding it is the surest way in using the staffe to take the
altitude close from the Horizon, because of the uncertayen opening that the
Mariners leave. Which altitude without respecte of parallaxis I call
the Apparent altitude. And then the surplus with the parallaxis is together
are to be abated to make the true altitude
altitude close from the Horizon, because of the uncertayen opening that the
Mariners leave. Which altitude without respecte of parallaxis I call
the Apparent altitude. And then the surplus with the parallaxis is together
are to be abated to make the true altitude
The quantity of which surplus I have set downe in a litle speciall
table here following according to the sondry distances of the ey from
the levell of the
table here following according to the sondry distances of the ey from
the levell of the
As when the ey is one pase that is 5 foote from the levell of the water, then the
abatement is . when 2 pases then & so forth as in the table.
Upon the poope of a tall ship the hight of the ey comonly is 4 or 5 pases &
then your abatement is or . Upon the decke in the waste . & at the
cheynes wilbe the abatement, which by triall with the load & line you may
abatement is . when 2 pases then & so forth as in the table.
Upon the poope of a tall ship the hight of the ey comonly is 4 or 5 pases &
then your abatement is or . Upon the decke in the waste . & at the
cheynes wilbe the abatement, which by triall with the load & line you may
And this you ought generally to note that whensoever you observe
with the staffe, you make good your high, iust when your ship is
on the top of the surge of the sea, otherwise you may
with the staffe, you make good your high, iust when your ship is
on the top of the surge of the sea, otherwise you may