In preparation for a catalogue of historical sundials, I have been
organizing the dials into classes based on the principal feature of the
celestial sphere or altazimuth coordinate projected onto the dial
surface. I would like your feedback on the list below.
It appears to me that self-orienting sundials combine two distinct
projections. Do you agree? What are they in the specific cases?
Here's the draft list followed by the ones I have questions about:
I. Directional sundials--project the hour angle of the sun onto the dial
surface
horizontal--particular (fixed latitude)
plate
garden
string-gnomon
compass
floating
cannon
reclining
horizontal--universal (multiple latitudes)
Butterfield-type
inclinable
vertical--particular (fixed latitude)
direct south (north, east, west) facing
declining
equatorial--particular
garden inclined plate
bow-string or crossed-Cs form
equatorial--universal
universal equatorial
Augsburg-type
Augsburg-type with cam
mechanical equatorial
spherical or globe
polar--particular
multiple-faced--particular
polyhedral
cruciform
cube
multiple-faced--universal
diptych
polyhedral inclinable
cube inclinable
cruciform inclinable
II. Altitude sundials
[generally for particular latitudes but some can be made universal]
ring
pillar
vertical plate
vertical disk
rectilinear--Capuchin
rectilinear--Regiomontanus-type
rectilinear--navicula
De Rojas-type
scaphe
horary quadrant
III. Azimuth sundials
simple azimuth--particular
pin-gnomon ??
analemmatic ??
magnetic azimuth--particular
magnetic azimuth and universal multiple-faced
Bloud-type diptych
IV. Astronomical compendia--instruments that combine multiple time finding
instruments, maps, or mathematical tables in a single package.
Here are the problematic ones for me-- Where should these be placed?
Universal ring dials and crescent dials--these are self-aligning, and so
must be more than simply directional equatorial dials. Are they
combinations of hour-angle and altitude sundials, or something else?
horizontal (or vertical) pin-gnomon--e.g. a sundial with a
vertical-(horizontal)-stick gnomon
often used to display Italian or Nuremberg hours
or to show time and date (or place of sun in zodiac) or lengths of
daylight.
?? is this an azimuth dial??
Oughtred-type dial (also called the "double horizontal dial") --a
combination of a a horizontal plate dial with a polar gnomon and one with a
vertical-stick gnomon--self-aligning
?? is this a combo hour-angle and azimuth sundial??
Analemmatic dial (modern form) with elliptical hour scale--is this an
azimuth dial?
Analemmatic dial (historical form) is a combination of a directional
horizontal sundial plus an elliptical analemmatic sundial on the same
plate. It is self-aligning.
Heliochronometer--standard definition? A solar chronometer that uses the
sun to find mean time directly. Where would this go in the
classification? An equatorial dial with a date cam?
Thanks for the help!
Sara
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