Solus FAQ


Why should I use Solus?

Solus is the most precise Sun and Moon data calculator of its kind available on the Internet.


Is Solus a free service?

Yes, for small-volume requests.  All users receive 24 free location results per month.


If I want to make lots/large requests, what does this involve?

Larger requests are performed on a commercial basis, at around 8 Cents ($0.08) per average (Class 1) request result [lower-precision request results are $0.03 (3 Cents) each.] The system works on the basis of pre-purchased credits (that are then used for making Solus requests).  You can purchase credits here.  Credits are priced on a sliding rate, see rates here.


How Accurate is Solus' Sun- Rise and Set times?

Very.  When the Earth's rotation is unaffected by environmental factors (these spike "randomly" every few days or so and affect the Earth's rotation sometimes by up to 20 seconds - although most of the time this is only a few seconds, usually less than 10 and typically 2-3 seconds), Solus' accuracy is very high for Earth rotation and geometric positions of the Sun and Moon.  Many variables are taken into account to arrive at results which match the visual-"real-life" version, including: air pressure, temperature, Earth curvature ("flattening"), high precision geometric positions of the Earth, Sun, Moon and planets, affects of the Moon and planets on Earth's position and orientation (precession and nutation), aberration, parallax, light-time delay as well as the terrain surrounding the requested site (affecting the altitude of the horizon at Sunrise/Sunset/Moonrise/Moonset.)


How Precise is Solus' Sun- Rise and Set times?

Solus uses high precision algorithms and returns timing results virtually 'to-the-second'.  Angular altitude results are also high precision.  Atmospheric refraction is calculated using local air pressure and temperature information (when provided, else it is approximated via Solus' internal climate model.  Cross-referencing NASA data has shown Solus' geometric Sun position accuracy to be within 0.1 arc second (approx. 0.00003) with results usually within 0.01 arc seconds (approx. 0.000003) and Moon position accuracy is within 3 arc seconds (0.0008), up to the end of this century (and Solus is still quite accurate beyond 2100AD.)


I used an 'official' source I found on the Internet to look up rise/set times and compared Sunrise and Sunset times and they are different to Solus' times.  Why?

The times calculated by some of the standard algorithms used by many organisations are often not very precise.  Other factors which can result in differences (between other sources and Solus) in predicted times are:

1] Solus assumes (as its standard setting, which can be adjusted, see here for instructions) that the observer is 1.5m above ground level.  Other calculators usually work on 0m - not very a plausible scenario "in real life" (since one usually does not view the Sun or Moon with one's head flat against  the ground.)  Though this does not intuitively seem to be something that would affect times by much, it actually does - by 12 seconds.

2] To accurately calculate atmospheric refraction (a big influence on actual rise/set times) Solus works out expected air pressure (roughly) and temperatures (fairly well) for the given location (and the altitude above sea level) at rise and set and can accept these variables manually for even higher accuracy.  Other calculators rarely factor in these influences, instead usually calculating a refraction index based on a fixed air pressure and temperature.

This makes Solus a very dynamic calculator and means that the data it produces matches - or is very close to - that actually observed.  Solus' accuracy has proven itself through observations.

3] Solus has a "terrain" mode.  In Terrain Mode Solus further automatically factors in the differences in altitude at the locations of Sunrise, Sunset, Moonrise and Moonset.  This yields even higher accuracy that matches actual scenarios. (Other calculators do not factor this into their calculations.)


What are the uses for solus?  Who can benefit from Solus?

Publishers of almanacs: Solus offers the most accurate information usually available to publishers of almanacs.

Weather forecasters: Solus can provide you with high-accuracy information for your forecasts.

Hot air ballooning: Solus can provide you with rise and set times for any given altitude, position and atmospheric condition.

Mountaineers: Ever wanted to know what time the Sun will set from atop a mountain or mountain peak you may wish to climb?  Solus can accurately provide you with these answers.

Astronomers: Solus calculates times for various twilight types and can also assist in other ways, such as providing high-accuracy Sun and Moon transit times and angular altitudes from any location on Earth.

Pilots: Pilots not rated for night flying can benefit from knowing accurate Sun rise and set times.

Radio operators: Radio operators can work out the best times to use their long range radios based upon potential affects/interference from the Sun.

Planners of large solar power installations and greenhouses.

Road users: Know when (by law) your headlights are supposed to be turned on/off.  In the case of disputes (e.g. with traffic officials) Solus can provide a definitive answer.

An additional benefit is that, if necessary, data can automatically be delivered in large volumes in raw and HTML format (for example, as in the case of weather stations or publishers of almanacs.)


If I want the rise and set times from a mountain peak then do I need to tell Solus what the altitude is for this location?

No.  Solus will automatically look up the altitude.  Simply enter the name of the mountain peak in question and Solus should already know it.  (Solus has a lookup database of many places worldwide, including mountains, mountain peaks, lakes and more.)  If Solus does not recognise the name of the mountain peak you request then simply enter the exact latitude and longitude instead.  Solus will then automatically look up the altitude for you.



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