Isocahedric Sundial - Parametric Latitudes

This kind of spherical sundial is called a “scaphé”.

It is a very precise sundial that can be used to determine date and hour.

Choose the sundial adapted to your latitude :

• 54° : Leeds (GB) - Hamburg (DE) - Minsk (BY) - Edmonton (CA)
• 51° : London (GB) - Praha (CZ) - Kiev (UA) - Calgary (CA)
• 48° : Paris (FR) - München (DE) - Wien (AT) - Quebec (CA) - Seattle (US)
• 45° : Torino (IT) - Vladivostok (RU) - Ottawa (CA) - Minneapolis (US)
• 42° :  Barcelona (ES) - Roma (IT) - Istanbul (TR) - Sapporo (JP) - New-York (US)
• 39° : Lisboa (PT) - Athens (GR) - Beijing (CN) - Washington (US)
• 6° : Lome (TG) - Colombo (LK) - Bogota (Bo)

How to use the sundial ?

• Put it on a flat and horizontal surface and orientated to the North.
• Use the top of the shadow to read date and hour.

Use it to know the date :

• The upper line is the Winter Solstice (December 21st)
• The downer line is the Summer Solstice (June 21st)
• The middle line is the Equinoxes (March 21st / Sptember 21st)

Use it to know the hour :

You will need to correct the solar time if you want to know the UTC.

• Add 1h in Winter and 2h in Summer if you have a seasonal correction of the time (such in West Europe)
• Add (west) or remove (east) a correction according to the distance with your reference meridian (10min for 200km at 45° latitude)

Praha : +1h (Summer) / +0 (Winter) - Paris : +1h50 (Summer) / +50min (Winter) - Torino : +1h30 (Summer) / +30min (Winter) - Istanbul : +1h

Example : June 10th in Dinan (West France / 48°) : 18h20 (solar) + 2h (Summer) + 10min (west of meridian) = 20h30 UTC

Use it to measure the Solstices :

• During the Winter Solstice, at 12h (solar time) the light will go through the 3 "horizontal" upper holes. You should see a light point on the table behind the sundial.
• During the Summer solstice, at 12h (solar time) the light will go through the “vertical” hole.

Print Settings :

• Printed on MK3S
• Filament tested : PLA
• Scale : from 66% to 200%
• Nozzle 0.4mm : 0.15mm and 0.20mm tested

Prusa Slicer 2.3.0