Field Equipment: Pocket Compasses

kronckew · 8th July 2009, 01:04 PM

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.

8th July 2009, 01:04 PM	#16
kronckew Member Join Date: Mar 2006 Location: Room 101, Glos. UK Posts: 4,215	for those who truly want to know everything: 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.