971486r
1.
2. Of taking of altitudes of the sonne or starre any
starre by the corsse staffe with more exactness
then hath ben used
2. Of taking of altitudes of the sonne or starre any
starre by the corsse staffe with more exactness
then hath ben used
The crosse staffe is is
the other instrument well knowne & used at sea
but and especially of starres. But as is it used hath ben used heretofore the
seamasters commit great errors then sometimes they are aware of
from which errors if it be purged it is then of more apte & certayne use
also for the sonne then ether the Astrolabe or Ring which I meane in
this chapter to
but and especially of starres. But as is it used hath ben used heretofore the
seamasters commit great errors then sometimes they are aware of
from which errors if it be purged it is then of more apte & certayne use
also for the sonne then ether the Astrolabe or Ring which I meane in
this chapter to
The staffe is devided with presuppose that the end thereof use observing should
stand in the center of the sight. And though that cannot be performed, yet
the common practiser thinketh there is little errour in putting of it
close under the that ey they behold withall: some under on the utmost corner of
that ey: some on the cheke bone: & & some on one side of the nose brid bridge of the nose.
All which placinges to some eyes, sometimes in some manner of observinges,
may prove true; & for the utmost corner of the ey to unproportioned eyes,
stand in the center of the sight. And though that cannot be performed, yet
the common practiser thinketh there is little errour in putting of it
close under the that ey they behold withall: some under on the utmost corner of
that ey: some on the cheke bone: & & some on one side of the nose brid bridge of the nose.
All which placinges to some eyes, sometimes in some manner of observinges,
may prove true; & for the utmost corner of the ey to unproportioned eyes,
But all eyes men that have not a seat for the staffe iust agaynst the center
of the sight, as most men have not, must needs find a full altitude still
& especially in great altitudes the errour wilbe great palpable as that it cannot
be borne withall, without artificiall correction; meaning allowance or
abatement, which hitherto have not ben made. And wher the seamen have
espied it by ether by great difference from there recconings, or comparison with
there Astrolabe; for such great altitudes they geve over the
of the sight, as most men have not, must needs find a full altitude still
& especially in great altitudes the errour wilbe great palpable as that it cannot
be borne withall, without artificiall correction; meaning allowance or
abatement, which hitherto have not ben made. And wher the seamen have
espied it by ether by great difference from there recconings, or comparison with
there Astrolabe; for such great altitudes they geve over the
How this errour may be knowne & reformed I have demonstrated & taught
11 yeares past in my booke called Arcticon. Now only I will remember unto
you out of the same, that which I shewed you sometime to fore & sufficient for
your
11 yeares past in my booke called Arcticon. Now only I will remember unto
you out of the same, that which I shewed you sometime to fore & sufficient for
your
The best place to set the end of your staffe is the utmost corner of the seat
of that ey which you mind to behold withall. because that place is firme &
certayne without offense to the eye.
And then how farre the end of [???] the staffe doth stand from behind the center of your
sight according as it hath ben already when by yourself by a staffe
I have for the purpose: I have marked in a spare place of these both your
staves nere the note of 90 Betwixt two parallel lines. And the same quantity I have found
to be in Cap. Whiddous; in Douglas the masters; & many [???] else, as in yours
& mine. The which quantity hereafter for brevity & order sake according to
the nature of the thing I call the per excentricity of the
of that ey which you mind to behold withall. because that place is firme &
certayne without offense to the eye.
And then how farre the end of [???] the staffe doth stand from behind the center of your
sight according as it hath ben already when by yourself by a staffe
I have for the purpose: I have marked in a spare place of these both your
staves nere the note of 90 Betwixt two parallel lines. And the same quantity I have found
to be in Cap. Whiddous; in Douglas the masters; & many [???] else, as in yours
& mine. The which quantity hereafter for brevity & order sake according to
the nature of the thing I call the per excentricity of the
The use of it is this: when you have according to the usuall manner
taken the sight of the sonne or starre & noted the place where the crosee stand
you are to remove him further from you & by such a quantity as the excentri-
city, which you may do by a pyre of compasses you are to consider what
sight that wilbe which is further from the ey by the quantity of the excentricity
which you may knowe by the helpe of a payre of compasses, [???] & doth
alwayes make it lesse then the former. And that sight or altitude is
as true as if the end of your staffe did stand in the center of your
taken the sight of the sonne or starre & noted the place where the crosee stand
you are to remove him further from you & by such a quantity as the excentri-
city, which you may do by a pyre of compasses you are to consider what
sight that wilbe which is further from the ey by the quantity of the excentricity
which you may knowe by the helpe of a payre of compasses, [???] & doth
alwayes make it lesse then the former. And that sight or altitude is
as true as if the end of your staffe did stand in the center of your