Date=10/15/ 1995 Julian Date=2450005.91943 UT=10:05 t T=-0.042137729 --- Mercury Venus Sun Mars Jupiter Saturn Uranus Neptune Eccentricity 0.20563 0.00677 0.01671 0.09340 0.04849 0.05552 0.04630 0.00899 Inclination 7.005 3.395 0.000 1.850 1.304 2.489 0.773 1.770 Perihelion Arg. 29.110 54.863 282.865 286.457 -86.158 -20.655 98.959 -83.674 Ascending Node 48.281 76.642 0.000 49.526 100.421 113.629 73.984 131.738 Mean Longitude 73.753 236.113 203.476 268.846 266.409 358.521 295.942 295.083 Mean Anomaly 356.362 104.608 280.611 292.863 252.145 265.547 122.999 247.020 Ecc. Anomaly 355.420 104.979 279.660 287.790 249.630 262.545 124.341 247.099 True Anomaly 354.359 105.354 278.715 282.613 247.047 259.400 126.504 246.626 True Longitude 71.749 236.858 201.580 258.595 261.310 352.374 299.446 294.689 Radius Vector 0.309 0.725 0.997 1.480 5.296 9.600 19.735 30.167 Ecliptic Long. 71.593 236.890 201.580 258.583 261.315 352.350 299.444 294.697 Ecliptic Lat. 2.784 1.148 -0.000 -0.898 0.427 -2.125 -0.550 0.503 Geocentric Long.185.090 216.345 201.580 236.120 252.864 349.162 296.561 292.805 Geocentric Lat. 1.031 0.506 -0.000 -0.607 0.386 -2.334 -0.554 0.504
Mean sidereal time is normally displayed. Apparent sidereal time is displayed when high precision calculations are in effect. Dynamical time should be OFF to compare the displayed sidereal time to values tabulated in the Astronomical Almanac in order for UT to be 0:00 at the tabulated Julian dates.
EQUATION OF TIME is calculated as the Sun’s mean longitude - Sun’s right ascension. This is a valid method of calculating the equation of time over a wide range of times.
LONGITUDE CORRECTION is the time difference from the center of a time zone to the current location. The displayed value changes whenever the longitude is changed.
SOLAR TIME is the apparent solar time for the civil time shown in the Time= field. This value is useful when working with any problems that use solar time such as those found in historical texts or when working with sundials or astrolabe instruments.
SUN ON MERIDIAN is the combination of the Equation of Time and Longitude correction for conversion from apparent solar time to zone time and is the time the sun will be exactly due south at your location. These three values are useful for determining true south and working with apparent solar time or sundials. This value is most accurate when the zone time is close to apparent noon, particularly when the sun’s declination is changing rapidly such as near the equinoxes.
The following values are tabulated for the Moon:
ASCENDING NODE is the longitude of the Moon’s ascending node. The longitude of the descending node is 180° from this value. You need to know the position of the Moon’s nodes to predict eclipses.
52 Using The Electric Astrolabe SEMI-DIAMETER is the Moon’s semi-diameter in minutes and seconds of arc. The value shown is the topocentric semidiameter (i.e. the value as seen from the surface of the Earth). This value is shown only when high precision calculations are on.
DISTANCE is the geocentric distance of the Moon in kilometers. This value is shown only when high precision calculations are on.
FRACTION ILLUMINATED is the fraction of the Moon’s disk that is illuminated and is approximately 1.000 for a full moon, 0.000 for a new moon, 0.250 for first quarter, etc.
POSITION OF BRIGHT LIMB. The precise term is Position Angle of the Bright Limb and is the angle from north of a line connecting the cusps of the illuminated part of the lunar disk. The orientation of the Earth’s shadow on the Moon changes depending on the Moon’s latitude. This figure measures the effect.
PHASE ANGLE is the angle from the Earth to the Sun as seen from the Moon. It will be approximately zero at a new Moon and 180° at a full Moon. The moment of a new or full Moon can be determined by comparing the Moon’s longitude to the Sun’s longitude. At full Moon, the longitudes will differ by 180° and they will be same at new Moon.
T shown on the page of full calculated variables (Alt+V) is the number of Julian centuries of 35625 days from epoch J.2000 (1/1/2000 0:00 DT) and is the coefficient for the polynomials used to calculate planetary positions. The ΔT next to UT shows that dynamical time is being used. The at the bottom of the screens indicates that high precision calculations are on. The value of ΔT in seconds is shown on the Ctl+V page and to three decimal places on the Help screen.
The current system clock date and time are updated each second on the V, Alt+V, Ctl+V and Help pages.
Help
Using The Electric Astrolabe 53 The help screen shows a summary of the commands and the status of each of the switches. As on the other text pages, you can enter new time and location values by typing over the value displayed. You can change the interval time for the F10 key by typing a new interval as the fraction of a day for each step. The settings for switches are shown when you change the switch by pressing the key corresponding to the switch. Two status values are not shown on the help screen; dynamical time is shown as a ΔT next to UT on the calculated values pages and high precision calculations are shown by a in the center of the bottom line of the same pages.
Figure 14. Cities and Added Objects.
A page of city locations is provided in order to make it easier to switch between locations. City names, latitude, longitude and time zones can be changed by just typing in new values and pressing Enter. A new city is selected by moving the highlighted cursor to the city name and pressing Ctl+Enter. The astrolabe for the new city is displayed automatically at the current date and time. When a new city is selected with Ctl+Enter the city name is displayed in the Description field of the Program Control page. The first city in the list is used as the default location when the Electric Astrolabe is started. The page of city names is selected with Alt+C.
Updated city names are NOT saved with a FILE unless the destination file is ASTRO.EXE. If you want to revise the list of locations, make the updates on the city page and then save a new default file to
ASTRO.EXE.
To add a new city permanently, follow these steps:
1. Enter the new city name, latitude, longitude and time zone and press Enter.
2. Go to the Program Control Page (C).
3. Go to the File: field. It is fastest to get to the file name field with Ctl+End.
54 Using The Electric Astrolabe 4. Make sure the file name is ASTRO.EXE.
5. Go to the Action: field. Press Enter until File appears in the field.
6. Press Ctl+Enter.
The city will now be in the list every time you start the Electric Astrolabe. Note once again that the first city in the list is your home location whenever the Electric Astrolabe is started. See Customization below for how to set a new city as the default location when The Electric Astrolabe is started.
UNDER WINDOWS 95, SAVING A NEW CITY LIST MUST BE DONE UNDER NATIVE DOS.
The locations of major world cities provided with the Electric Astrolabe were taken from The New International Atlas (Rand McNally, 1991). There are many sources for the latitudes and longitudes of locations. Particularly accurate sources include geodetic survey maps and sectional maps used by pilots and Google Earth. A good source for time zone information is the International Airline Guide.
Using the Electric Astrolabe to hop between cities has been useful for determining the hours of daylight for trip planning, duplicating conditions for a specific location such as an observatory and following history in the making by noting the astronomical conditions during historic events.