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magnitude and dot size. The next nine items all control the display of labels for stars. They cycle from Auto to On, then to Off, then to Auto again: a three way switch. When a marking is on On or Off, Guide will ignore its own judgment and either always show or always not show the marking. When it is on "Auto", Guide uses a predetermined set of rules designed to minimize clutter. "Mag Labels" labels all stars, down to the indicated brightness level, by magnitude. You might have a chart showing stars down to magnitude 15, but you wouldn't want all of them labelled by magnitude; it would be too crowded. So you would set a limit of (perhaps) magnitude 11 here. If you set a "proper motion vector" length of, for example, 1000 years, each star will appear with a short line indicating the direction and amount of its motion over 1000 years. By increasing this value, you can get the motions of slower stars to be apparent. A value of 1000 years is used in the charts of the Millennium Star Atlas, and seems to work well in most Guide charts as well. Some people find these vectors to be distracting; therefore, the default length is 0 years (that is, no vector at all.) "Non-Stars" toggles the display of objects labelled as "non-stars" in the Hubble Guide Star catalog. The GSC was automatically generated, and a computer classified non-starlike objects on the photographic plates (scratches, asteroids, galaxies, nebulae, and some stars that confused the computer) as "non-stars". Most are really misclassified stars, so Guide displays them by default in green. If you don't want to see them, shut them off with this switch. By default, Guide shows bright stars using their visual magnitudes on the Johnson photometric system, called "Vj". (This is true for stars from the USNO A2.0 catalogues, described on page 59, or the Tycho catalogue, described on page 73.) Click on the "Vj" box, and you get a choice of alternative photometric systems. Select one, and Guide will switch to use of that system. Please be aware that this is far from a perfect system, mostly because the data is far from perfect. GSC stars, and stars from most "user-added datasets", are unaffected by your choice of magnitude system, because the data simply doesn't exist. In other cases, for example when computing Ic (Cousins infrared) magnitudes, Guide has to estimate a magnitude using (for Tycho stars) VT and BT data. The result is usually in the right area, but shouldn't be relied upon for precision work. If you select "Color stars", Guide defaults to showing them with very bright, saturated colors. Red stars are fire-engine red, yellow stars are canary yellow, and so forth. Of course, stars actually appear visually to have much milder colors. You can replicate this
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