| DECLINATION LINES October 25, 2009 |
The free booklet Declining Shadows (and its
DeltaCAD macro (calendarDeclination.bas) here,
and you can set the declinatio values) are very
well worth downloading. This is only an extract
from the section in Illustrating More Shadows
which deals with calendar curves in depth, and
discusses several trigonometric approaches, and
provides complete tables for a wide range of
style heights (latitudes). Also see here.
The DeltaCAD programs display calendar curves,
as does one of the JustBASIC programs, and of
course the main spreadsheet
reference-spreadsheets.xls which has many ways
of calculating declination line data.
The DeltaCAD macros provide for animation
showing how declination curves vary. They also
show how they vary by nodus to dial plate height,
or, by style length. The results appear
inconsistent, but they are not, and as with all the
DeltaCAD animations, they are highly instructive.
DeltaCAD macro (calendarDeclination.bas) here,
and you can set the declinatio values) are very
well worth downloading. This is only an extract
from the section in Illustrating More Shadows
which deals with calendar curves in depth, and
discusses several trigonometric approaches, and
provides complete tables for a wide range of
style heights (latitudes). Also see here.
The DeltaCAD programs display calendar curves,
as does one of the JustBASIC programs, and of
course the main spreadsheet
reference-spreadsheets.xls which has many ways
of calculating declination line data.
The DeltaCAD macros provide for animation
showing how declination curves vary. They also
show how they vary by nodus to dial plate height,
or, by style length. The results appear
inconsistent, but they are not, and as with all the
DeltaCAD animations, they are highly instructive.
For other dial furniture, look at the Italian line page page
For other dial furniture, look at the analemma page
The analemma page has excellent DeltaCAD macros discussing not just the analemma, but also the
calendar curves.
However, this calendarDeclination.bas macro allows you to specify the declination values to use for all
the dials, whereas the analemma.bas macro has fixed values except for a few cases.
The analemma uses the EOT (equation of time) together with the sun's declination to derive the
analemma, and that same declination is the basis for calendar curves. Actually, that is true for armillary,
equatorial, polar and meridian dials. For horizontal, vertical, and vertical decliners, the sun's azimuth
and altitude are used as well. And those analemma notes are helpful in understanding what is going
on. Chapter 24 of Illustrating Time's Shadow is by far the best description available. I think.
calendar curves.
However, this calendarDeclination.bas macro allows you to specify the declination values to use for all
the dials, whereas the analemma.bas macro has fixed values except for a few cases.
The analemma uses the EOT (equation of time) together with the sun's declination to derive the
analemma, and that same declination is the basis for calendar curves. Actually, that is true for armillary,
equatorial, polar and meridian dials. For horizontal, vertical, and vertical decliners, the sun's azimuth
and altitude are used as well. And those analemma notes are helpful in understanding what is going
on. Chapter 24 of Illustrating Time's Shadow is by far the best description available. I think.
| For calendar curves on any hour angle dial with analemmas, check this page here. However, this calendar macro allows more flexibility on specifying declination values. |