Orion 7880 instruction manual Variable Stars, Catalog ST Stars

the “S=” refers to the separation between the two brightest stars. The “M=” now refers to the magnitude of the brightest star.) To go to the next double star in the selected con- stellation, simply press the up arrow button. The guide arrows will now direct you to the next double star in the constellation. If there are no more double stars available in that constellation, a double star from the next constellation (in alphabetical order) will be dis- played. To select another constellation in which to view a double star, press the Star but- ton, select “DOUBLE”, and pressEnter.

Variable Stars

Variable stars are stars that change their brightness, also called magnitude, over time. The period of brightness change varies greatly from star to star; some variable stars change brightness over several days while others may take several months to noticeably change. It is fun and challenging to watch a star’s magnitude change over time. Observers typically compare the current brightness of the variable star to other stars around it (whose magnitudes are known and do not change over time).

To select a variable star to observe, press Enter after selecting “VARIABLE” from the Star button choices. The LCD screen will then display the word “VARIABLE” with a flash- ing three-letter constellation designation after it. Now, select the constellation in which you would like to view a variable star. Use the arrow buttons to scroll through the list of con- stellations. If you are unsure which constellation the three-letter designation represents, refer to Appendix C. Once you have selected the constellation, press Enter. A variable star in that constellation will now appear on the LCD screen, along with the guide arrows to lead you to the variable star. The current constellation is shown in the lower left, and the variable star’s name is in the lower right.

Note: Variable stars typically have names like “Eta” (Greek letter designation) or a letter designation like “R.” The full names for these variable stars are actually linked to the con- stellation they reside in. For example, in the constellation Aquila, these stars would be “Eta Aql” and “R Aql.”

For more information about the variable star selected, press the Enter button. (The “M=” refers to the mean magnitude of the variable star.) To go to the next variable star in the selected constellation, simply press the up arrow button. The guide arrows will now direct you to the next variable star in the constellation. If there are no more variable stars avail- able in that constellation, a variable star from the next constellation (in alphabetical order) will be displayed. To select another constellation in which to view a variable star, press the Star button, select “VARIABLE,” and pressEnter.

Catalog (ST) Stars

The “ST” catalog contains all of the stars in the IntelliScope Computerized Object Locator’s database. This catalog has 837 of the most interesting stars to view in the night sky. The full list of stars appearing in the ST catalog is printed Appendix D. Generally, the best way to use the ST catalog to observe stars is first to peruse Appendix D, and then note the catalog number of the star you wish to observe.

To select an ST catalog star to observe, press Enter after selecting “CATALOG” from the Star button choices. The LCD screen will then display the letter “ST” with three digits blinking after it. Now, input the ST catalog number of the star you wish to observe, and press Enter. If the ST catalog number of the star you wish to view contains three digits, it is not necessary to press Enter after inputting the third digit.

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