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large buttons are about twice the size of the standard buttons. Large buttons are not available for all options; in such cases, the small buttons are used instead. 8a: Location dialog The Location dialog controls your point of view on the earth (or on other planets and satellites). The dialog looks like this: Earth Longitude: W 69.900 Latitude: N 44.010 Altitude: 100m Enter location name [ ] Use geocentric position [ ] Include refraction Humidity: 20% Temperature: 20 C Pressure: 760 mm Hg The very first item tells you from where you are looking at the sky. If you click on it, you will get a long list of Solar System objects. You can select one, and after that, all planets, moons, and so on will be drawn from that planet (or satellite). You can see what Jupiter and its moons look like from one of Jupiter's moons, or what the Earth looks like from the Moon or other planets. (The view of the inner moons of Saturn as viewed from Japetus is particularly recommended.) This can be very interesting and educational, although most Guide users cannot physically travel to other planets or to near-Earth orbits. Most Guide users can set their viewpoint on the Earth with the "Enter location name" button. Click on this, and enter the name of your city or town, and Guide will (usually) figure out the corresponding latitude and longitude. In the US, this can be a name plus two-letter state abbreviation: "Augusta, ME", or "Houston, TX"; or it can be a five-digit postal (ZIP) code, such as "04008". Outside the US, it can only be a name, and unfortunately, the number of recognized cities is not very great. So most people will have to enter a latitude/longitude position. This can be found on most maps, or with a GPS receiver. You usually do not need to be nit-pickingly precise about this. Guide uses your place on the earth to calculate rise and set times and to get better accuracy on planetary positions. (For example, a solar eclipse visible on one part of the earth may not be visible at another, because the moon isn't exactly in the same spot in the sky.) An accuracy to a degree (meaning about 111 kilometers or 70 miles) will get rise and set times to within about four minutes. But if you want to get good positions for artificial satellites, or times for eclipses and occultations, you will want an accuracy of at least one kilometer.
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