Rise/Set/Transit Times for Major Solar System Bodies and Bright Stars
This data service provides the times of
rise, set, and transit for
the major solar system bodies and selected bright stars. The output table also
includes
azimuth
at rise and set, as well as
altitude
at transit.
Data will be provided for the years 1800 through 2050.
Use the buttons under Location to find coordinates of cities or towns in the U.S. or its territories,
or to convert between Degrees-Minutes-Seconds (DMS) and Decimal Degrees.
Be sure to read the Notes section (at the
bottom of this page) for definitions and additional details on the data.
Notes
The altitude and azimuth values are for the center of the apparent disk of the object.
The altitude values include the effect of atmospheric
refraction
when the object is above the
horizon
.
The azimuth values are computed with respect to true
north (not magnetic). For instructions on using a true azimuth (bearing)
with a compass, see
NOAA's
Geomagnetism FAQs
. To determine the magnetic declination for a specific location and date,
see
NOAA's
Geophysical Data Center - Magnetic Declination calculator
.
Height
The user can specify the height of the observer, which can range from the surface of the Earth
to a maximum of 10,999 m (the top of the troposphere). It is assumed that the observer's horizon
is flat (i.e., no geometric 'dip' is applied) and unobstructed. However, since the light at
altitude passes through less atmosphere than it does at sea level, the refraction of the light
does vary with height. In most circumstances these changes are small, usually less than a minute
in rise/set time.
Since the rise/set times are printed only to the nearest minute, most users will not see any
differences.
However, at high latitudes, the times can vary by several minutes (e.g., see Barrow, Alaska
around January 22-25).
Refraction
This data service incorporates a model that determines the angular refraction by numerically
integrating a ray passing through a simple polytropic atmosphere. The model is based on the
method described by Hohenkerk and Sinclair [1] and by
Hohenkerk [2].
Precision
Rise and set times are tabulated to a precision of one minute only (i.e., no
seconds are tabulated). This is because the observed times of rise and set are affected
by random changes in local atmospheric conditions and other local variables which cannot
be accurately modeled. Thus, tabulating the times to a higher precision is not practical
or normally useful.
Output Table Symbols and Blanks
Blanks or extra lines may occur in the table.
An extra line will occur when two of the same phenomenon occur on a given
day. Such an event may occasionally occur for the rise, set, or twilight of solar system
bodies at high latitudes, or for transits of any solar system body (except the Sun)
at any latitude.
Blanks indicate that a particular phenomenon did not occur on the given day.
Blanks may occur for a couple of reasons: in the tables in high latitude
situations where the object may rise and then be continuously above the horizon
for an extended period of time, or conversely finally set after being above the
horizon for an extended period of
time. Blanks may also occur in a rise/set table as the time of rise/set changes across a day
boundary (e.g., Sun sets later and later in the day as summer approaches). Blanks may also
occur in the moonrise/moonset table because the time between successive moonrises or moonsets
is about 25 hours or about one hour longer than the 24 hour day. Consequently, these gaps in
the moonrise/moonset table occur approximately once every 25 days.
The following symbols may appear in the output table:
Rise/Set Table Symbols
| Symbol |
Definition |
| ***** |
There is no event because the object is continually above the horizon. |
| ---- |
There is no event because the object is continually below the horizon. |
| N |
Altitude at local transit is measured
from the northern horizon. |
| S |
Altitude at local transit is measured
from the southern horizon. |
| ????? |
Phenomenon is indeterminate. |
For Sun calculations for high latitudes, one may also see these symbols
in the twilight columns:
Twilight Symbols
| Symbol |
Definition |
| ///// |
There is no event because the Sun is
continually above the twilight zenith distance. |
| ---- |
There is no event because the Sun is continually below the twilight zenith distance. |
Time Zones
When using the
"Need USA Location" button, the service will fill the
Time Zone hours field and set the Time Zone direction button according to the current standard
time zone of the US place entered.
The railroads introduced standardized
time zones to the USA in
1883. Since then, time zone boundaries have evolved considerably, with many cities and
counties shifting from one zone to another. This service makes no attempt to track such historical changes.
For locations that require it, you may enter the time zone in decimal hours.
For example, for locations in India,
you may enter 5.5 hours east of Greenwich for
the time zone. The time zone field can accommodate up to five characters.
- Hohenkerk, C.Y. & Sinclair, A.T. 1985, "The computation of angular atmospheric refraction
at large zenith angles,"
NAO
Technical Note No. 63
(Taunton, UK: H.M. Nautical Almanac Office)
- Hohenkerk, C.Y. 2013, "Positions" in The
Explanatory Supplement to the Astronomical Almanac, 3rd edition, ed. Urban, S.E. and Seidelmann, P. K.
(Mill Valley, CA: University Science Books) section 7.2.7.1, p. 277
