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Portable Sundials in the Modern World

Using sundials in daily life today may seem impractical. For those uninterested or interested only in the novelty of bygone technology, the thought of pulling out a pocket dial throughout the day rather than a smartphone likely seems horribly pointless, cumbersome, and regressive. Even for many sundial enthusiasts, the concept may seem romantically appealing yet unrealistic. For those dedicated few, however, those who appreciate the beauty in anachronism and the intrinsic value it offers, the prospect can become feasible.

By relaxing our expectations of atomic accuracy and approaching the challenge with the fluidity, dedication, and preparation necessary to rewrite our relationship to time and the natural world, the practice of using these ancient tools in a modern context begins to crest the horizon of impossibility.

When approaching this topic, it is important to keep in mind that a sundial is not a 1:1 replacement that matches the utility and intuitiveness of modern timekeepers. It is, by many accounts, an obsolete instrument built for a society and mentality fundamentally different from our own. Due to the modern invention of standard time, many people do not understand that time was ever linked to the position of the sun. It is the responsibility of the user to carry conceptual information, such as the equation of time, that allows the dial to reconcile the centuries of societal change.

Never before has a culture been so disconnected with its relationship to the natural sphere. In terms of celestial motion, few see anything more than beauty and wonder in the turning skies. Despite the cultural necessity for this understanding being at an all-time low, the utility and sense of grounding gained through understanding the ways the celestial sphere can be harnessed and channeled is as valuable and personally enriching as it was centuries ago. Technology today is largely a dominion over our world and its forces, but the potential remains for technology that collaborates with nature, weaving together the human wrought and the natural to yield genuinely useful outputs that are more fulfilling to access than glancing down at a screen.

Today, the concept of time has become fundamentally severed from the apparent motion of the sun. Many conceptualize noon not as the sun's culmination, but as 12:00 on a digital display. This reliance on instruments that tell time rather than those that measure time has caused the common understanding of celestial movements to slip into obscurity. An enhanced understanding and awareness of these natural movements is in part a prerequisite, but is more so an illuminating byproduct of sundial use. The simple act of regularly using a sundial links one's conception of time with the natural world, expanding their awareness of its processes and cyclicality. An understanding of civil time's basis on a fictitious sun and knowledge of how to reconcile it with the true sun will drastically streamline the everyday use of sundials. Keeping a mental or physical note of the current EoT and your longitude correction will improve not only your sense of worldly perspective, but the accuracy and reliability of your dial.

I speak about expanded natural awareness through sundial use and a sense of celestial perspective, but these are not tangible things that can be easily incentivised through words. What I describe is an extremely personal endeavour, and must be pursued and navigated individually. I encourage anyone who finds this appealing to research further, both through scholarship and hands-on experience.

 

In the paragraphs that follow, I will explain the particular dials that I believe to be the most realistic options for serious contemporary use. The selection is–again–very personal, as the ideal model depends on the lifestyle, geographical location, and personal preference of the user. For the purposes of this catalogue, I have omitted single-latitude dials in lieu of common hour"universal" dials. While all universal in name, some of the following dials feature operational ranges more narrow than others. These details will be noted under the "pros and cons" of each dial.

Universal dials with built-in magnetic compasses

These compass dials are perhaps the most straightforward to operate. Because they incorporate a magnetic compass, they are simple to orient visually. These dials are often universal, lending themselves to those who frequent different latitudes.

The largest potential drawback to these dials is their reliance on the compass for orientation. Because magnetic declination is not consistent globally or temporally, it may need to be corrected periodically. Magnetic declination must be accounted for via marking or adjusting the compass itself.

To insure an accurate reading, the dial must also be set on a level surface. This may prove difficult if the user intends to use the dial in their hand.

There are many dials that fall into this category, some common examples including Nuremberg (equatorial), inclining, Butterfield (horizontal), and diptych dials. The average diptych dial may be the most convenient to use, but their often limited range of latitudes is most fitting to those who do not plan to travel far from the location of its design*. For those desiring the widest range of latitudes, the Nuremberg type dial may be the optimal choice.

Diptych, Butterfield

Pros:

- Simple to use and orient

- No confusion of morning and afternoon hours

- Cases may contain lunar volvelles (allowing the dial to be used in moonlight)

Cons: 

- Limited range of latitudes

- Require level surfaces

- Some time is required to allow the compass to settle

- Magnetic declination must be attended to

Augsburg, Inclining

Pros:

- Simple to use and orient

- No confusion of morning and afternoon hours

- Case may contain lunar volvelles (allowing the dial to be used in moonlight)

- Full range of latitudes

Cons: 

- Requires level surface

- Some time is required to allow the compass to settle

- Magnetic declination must be attended to

* Certain diptychs feature a wealth of useful features other than the common hour such as calendars, lunar volvelles, wind vanes. These features can all be very useful, but do not negate the fact that the range of latitudes is often quite limited.

Where to find:

Diptych

- Polvere Di Tempo

Butterfield

- Punto Vernal

Inclining

- No specialty dealer known; found commonly online alongside nautical decor

Augsburg

- Hemispherium

- Part of the 1987 Franklin Mint collection "Great Instruments of Discovery," available through various resellers

Universal altitude dials

These dials offer considerable accuracy for those willing to take some time to learn their mechanics. Although they present a steeper learning curve than hour-angle dials, the range of utility and convenience these dials offer is also considerably elevated.

Two prominent examples of universal altitude dials are the Regiomontanus rectilinear and the trigonus (universal projection) dial. The Navicula may also be considered, though it is effectively identical in function to the Regiomontanus dial. As altitude dials, these sundials can be very thin, the Regiomontanus in particular often constituting no more than half an inch of depth.

These dials do not require a compass to operate, only referencing the altitude of the sun. Because of this, however, the user must determine the correct of two readings which share the same solar altitude. Additionally, due to the universal nature of the dial, it is required to know and set the date and latitude before taking a reading. Conversely, this universality allows the dial to identify the hours of sunrise and sunset for any given date.

Certain models of Regiomontanus rectilinear dials can be used to find the time at night using the stars.

While both universal in name, only the trigonus dial features a full range of latitudes. The Regiomontanus features an impressive range itself (often 30ºN–60ºN at minimum), though cannot be considered truly universal.

Regiomontanus

Pros:

- Precise readings

- Very thin profile

- Can take readings very quickly, assuming the date and latitude have been set for the day

- Can function even without direct sunlight, as long as the altitude of the sun can be identified (e.g. when the sun's outline can be seen behind a cloud)

- Very wide range of latitudes

- Can determine the hour of sunrise and sunset for any date

- May accommodate time-finding via the stars.

- Used while suspended

Cons: 

- Strong winds may disturb the plumb bob and make readings difficult

- User must know either if the reading taken is before or after noon, or the rough direction of north

- Hours taken around noon are difficult to determine

- User must know the date and latitude

Trigonus

Pros:

- Precise readings

- Full range of latitudes

- Used while suspended

Cons: 

- Strong winds may disturb the plumb bob and make readings difficult

- User must know either if the reading taken is before or after noon, or the rough direction of north

- Hours taken around noon are difficult to determine

- User must know the date and latitude

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Where to find:

Regiomontanus

- Master Terebrus

- Helios Sundials

Trigonus

Master Terebrus

Equatorial ring dial

The self-orienting armillary dial (most commonly known as the (universal) equatorial ring dial) exists at the height of portable sundial design. Its principles combine elements of hour-angle and altitude dials, allowing the dial to position itself true north without the aid of a compass. Sometimes, these dials feature a quadrant inscribed on the meridian ring, allowing the user to determine local latitude.

This self-orientation is possible because of a central date scale and nodus replacing what might be a polar gnomon on other equatorial dials. This results in the user needing to know and set the date prior to use. In addition to the date scale, the dial features a full latitude scale which must also be set prior to use.

When not in use, the equatorial hour ring can fold into that of the meridian, reducing the dial to negligible depth.

In addition to displaying solar time and true north, the equatorial ring dial also serves as a model of the celestial sphere with the nodus assembly acting as the celestial axis and the hour ring as the equator. The position of the nodus along the date scale also allows the user to visualize the sun's position in the ecliptic north or south of the equator.

Although intuitive, the meridian ring obscures the nodus' beam at noon. Likewise, since the sun's path at the equinox coincides with the equator, the equatorial ring blocks the nodus' beam on the equinox, rendering the dial relatively unreliable at that time (see demonstration of this effect).

Similarly to altitude dials, when the date and latitude are set, the equatorial ring dial identifies two potential hours when rotated. Because of this, the user must determine the correct of the two readings which share the same solar altitude. This makes the dial difficult to use around noon.

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Where to find:

Equatorial ring dial

- Kala

- Helios Sundials

Equatorial ring dial

Pros:

- Precise readings

- Very thin profile

- Can take readings very quickly, assuming the date and latitude have been set for the day

- Full range of latitudes

- Used while suspended

- Dial functions as a solar compass, pointing true north

- Dial serves as a model of the celestial sphere

- May include quadrant for determining latitude

Cons: 

- User must know either if the reading taken is before or after noon, or the rough direction of north

- Hours taken around noon are difficult to determine

- Cannot reliably function on the equinox

- User must know the date and latitude

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