Field Equipment: Pocket Compasses

[kronckew]

i have always been fascinated by sundials.

i frequently use the one in my garden as a backdrop for my blade photos. i use a simple flat dial with a gnomon set at the local latitude angle.

here shown upside down as the blade is the star.

i used to have an armillary sphere there,

but it was a bit hard to read. lives on my window sill now. i also have a sheperd's stick sundial like this one somewhere:



Also known as a Pillar Dial, this is one of the earliest and most widespread forms of sundial. To use, the folding gnomon is swung around to the correct position for the time of year (the months are indicated by letters around the base). The sundial is then suspended so that it hangs vertically. The shadow of the gnomon then falls straight down and ends somewhere between the hour lines. Each line represents either an hour of the morning or afternoon, as it works by plotting the rise of the sun till noon and its subsequent fall. This type of sundial is specific to a particular latitude, and this one is set for a latitude of 52 degrees. Originally carved in ivory, bone or wood, this example is cast in resin with pewter fittings.

another is the more futuristically modern all plastic optical one here:



the gnomon is actually a circular acrylic prism that focuses the sun into a pointer along the dial. it has an inbuilt spirit level, compass and angle adjustment as well as a vernier for adjusting the equation of time corrections. the dial rotates like an old circular slide rule to allw compensation for time zones. all fits into itself for travelling. it is accurate to the minute.

and finally, here's one i made earlier: these are called diptych dials



very similar to the 'da silva one above, but tells time on both the horizontal and vertical parts. the string is set at a general angle for the latitude, but you can adjust by trimming the base to compensate for your precise latitude if desired.

[kronckew]

the sun is of course, not cooperating today, so they are not actually showing the time.

if you are into making your own, here's the page that shows six types of sundial. LINKY, including the diptych

these are many other types of sundial, and many unusual portable ones, google for more info....

edited:

found an online cc. of an optical one like mine actually in the sun



someone actually makes a digital sundial:



quite clever, i'll have to buy one of those i think. uses fractal geometry to make thin optical filters in the upper section that illuminate as mirror imaged digits which reflect correctly in the base mirror.

if you have a large garden, here is a fun one, the analemmatic,

which can be made in simple stepping stones like above. YOU are the gnomon, as in this one:

you stand on a sliding scale that corresponds to the month
there was a website that will calculate the plans and let you print it out, depends on location. there are also some freeware and shareware progs that calculate & let you print plans for a wide assortment of sundials for your house or garden. or your pocket

[fernando]

May i introduce these two little instruments; better say, replicas, probably functional, bought in the souvenir shop French Chateau d'Ussé, back in 1992.
One is a brass ring, with a sliding mid section with a hole that allows the sun to goin in and point the hours in the opposite inner side. It has readings for the months of the year, as may be seen in the outer part. It also has an inscription, probably engraved in the original it was replicated from: . TO.H.S.THON ANNO.1721.
Amazingly, i have just had the idea to browse these initials in the web, and look what i found:
http://www.abc.net.au/tv/collectors/txt/s2288621.htm

The other is a silver articulated double arch, and it has readings (latitudes) for the cities of Paris, Florence, Hamburg and Heilderberg.

Both items were sold with an instructions book, but i don't know where they are by now.

Have you guys ever seen such things?

Fernando

.

[fernando]

Better:

http://www.nmm.ac.uk/collections/exp...cfm?ID=AST0252