第7课 - 搜索天体


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henrysting --22:00 2005-3-22 (CTS)

In the previous lesson we saw how to display information about any object on the map. That's a very useful capability, but SkyMap contains many millions of objects, and we may not always know where the object we want to know about is located in the sky. Another problem we have to contend with is the fact that most objects are known by many different names and catalog numbers, and the name we're interested in may not be the name which SkyMap uses to label the object on the map. For example, the bright galaxy "M86" is also known as "NGC 4406", "UGC 7532", "MCG 2-32-46", "CGCG 70-72", "PGC 40653", and "VCC 881", to name only a few of its numerous catalog numbers; if we read an article which referred to "UGC 7532", and then saw a galaxy labelled "M86" on the map, we probably wouldn't know that it was the same object! Fortunately, we don't need to memorize all the different names and catalog numbers each object has; SkyMap makes it easy to locate any object using any of the names that object may be known by.

上一课我们了解了如何显示天图上任何一个星体的信息。那是很有用的功能,但是SkyMap包括数百万个天体,而我们并不总是知道要找的天体在天空的哪个位置。另一个我们必须面对的问题是大部分天体都有许多不同的名字和星表编号,我们所知道的名字不一定是SkyMap用以标称该天体的。比如,亮星系M86又叫做“NGC 4406”、 “UGC 7532”、 “MCG 2-32-46”、“CGCG 70-72”、 “PGC 40653” 或者 “VCC 881”,而这还只是它众多星表编号中的一小部分。如果你读到一篇关于“UGC 7532”的文章,又在天图上看到被标为“M86”的天体,可能不会意识到它们是同一个天体。还好,我们不必记住每个星体的全部名称和编号,在SkyMap中,用该天体的任何一个名称都能很容易地在星图上找到它。

Searching for a planet, Sun, or Moon


Let's search for a planet on the map. Run SkyMap, move the mouse pointer to the menu bar at the top of the SkyMap window, and select the Search/Planet... menu item:



The "Find planet" dialog will be displayed:



Use either the cursor keys or the mouse to select any name in the list, then click the Goto button. The map will be redrawn centred on the selected planet (Mars in this case):



The white square is called the "search target marker", and marks on the map the location of the object which has most recently been searched for. Scroll the map around the sky, or change the view level by pressing the number keys; you'll find that the marker will remain on the map. To make it disappear, select the View/Hide Search Target menu item, or press the “T” key on the keyboard.


Now try displaying the information dialog for a planet directly, without having to first locate the planet on the map and right click on it. Display the "Find planet" dialog as you did before, select a planet (or the Sun or Moon), and this time click the Info button. The information dialog for the chosen object will be displayed.


Searching for "deep sky objects" by popular name


A "deep sky object" is any object outside our solar system except a star; the name is a "collective term" used to refer to such things as galaxies, star clusters, nebulae, and so on. All deep sky objects have catalog numbers - indeed, most have many catalog numbers as we've already seen! Many of the brightest deep sky objects also have "popular names" by which they're often referred to, such as "Andromeda Galaxy", "North America Nebula", "Blinking Planetary", and so on. SkyMap lets use search for deep sky objects using either a catalog number or a popular name.


Let's see how to do this. Run SkyMap, then press the number "5" on the top row of numbers; you'll now be looking at a fairly "close up" view of some arbitrary part of the sky. Let's look for the "Andromeda Galaxy" - a large galaxy visible to the naked eye in dark skies as a faint patch of "mist", and easily visible through binoculars from anywhere in the northern hemisphere. Move the mouse to the menu bar at the top of the SkyMap window, and select the Search/Deep Sky Popular Name... menu item:



Doing this will display the "Find object by popular name" dialog box:



The list on the left side of the dialog lists all the popular names which SkyMap knows about; use either the cursor keys on the keyboard, or the scroll bar to move up or down the list. On the right side of the dialog are three buttons:


  • Goto, which moves the map to the location of the object currently selected in the list.


  • Info, which displays the information dialog for the selected object, leaving the map unchanged.

信息 显示所选天体的信息框,保持星图不变。

  • Cancel, which allows us to change our mind, and exit the dialog without doing anything at all.

取消 如果你改变了主意,可以退出对话框,不作任何改变。 We want to locate the Andromeda Galaxy on the map. Look at the list of names, and you'll see "Andromeda Galaxy" close to the top of the list. Click on the name to select it (or use the "down arrow" key on the keyboard), then click the Goto button. The dialog will disappear, there will be a brief pause while SkyMap draws a new map, and then the map will appear looking something like this:



Note the large "oval" of the galaxy, with the name "Andromeda Galaxy" below it. As always, the search target marker - the white square - shows which object has been located by the search.


Try searching for some of the other objects in the popular name list in the same way; you'll soon find that some are shown on the map after the search operation, but others aren't. That's because the search operation always takes you to the position of the object being search for, but the current map settings often mean that the object itself isn't visible; we'll learn how to change map settings later.


It's very often the case that all we want to do is display information about an object, rather than actually see it on the map. To do this, use the search dialog in exactly the same way you did before, but this time, click the Info button rather than the Goto button; this will leave the map unchanged, and simply display the information dialog for the selected object.


Searching for deep sky objects by catalog number


Most deep sky objects don't have a "popular name" - if we want to find them, we need to know their catalog number, or at least one of their catalog numbers, since most objects have several. Most objects visible in small telescopes with either be in the "Messier Catalog" or the "New General Catalog", and will have catalog numbers starting in "M" or "NGC" respectively.


Let's look for the bright galaxy M86 which we talked about at the start of this lesson. If SkyMap isn't already running, run it, and this time press "7" to display a level 7 map of some arbitrary part of the sky. Select the Search/Deep Sky Catalog Number... menu item:



Select this menu item and the "Find deep sky object by catalog number" dialog will be displayed:



Type "M86" into the text field, then click the Goto button to locate the object. The map will be redrawn, with the white search target marker showing the position of M86:

在文本栏里键入“M86”,点击Goto键。星图会重绘,由白色搜索标识指示出M86的位置 :


Remember that we said at the start of this lesson that M86 had many other possible names as well? Repeat the above procedure, but this time search for "UGC 7532"; you'll find that exactly the same map will be displayed - "UGC 7532" ("UGC" stands for "Uppsala General Catalog of Galaxies") is an alternative name for "M86". This illustrates an important point - when you search for an object, the name with which the object is labelled on the map will not necessarily be the same as the name that you searched for, but the search target marker will always show the correct position of the object.

在开头我们提到M86也有许多名称,重复上面的过程,但是这次搜索“UGC 7532”;你会发现显示的是同一张星图,UGC 7532(UGC代表Uppsala General Catalog of Galaxies乌普萨拉星系总表)也是M86的别名。这说明了重要的一点:在搜索天体时,星图上显示的名称并不一定就是搜索的名字,但是搜索标识总能指示天体的正确位置。

Searching for a star


To search for a star, select the Search/Star... menu item; the "Find star" dialog will be displayed:



This dialog allows you to locate stars using many different methods; if you press the F1 function key whilst the dialog is visible, they will all be explained. We'll describe here three of the most commonly used methods of identifying stars. The important thing to remember about this dialog is that all that SkyMap takes any notice of is what's in the "Star name" text field at the top of the dialog - everything else on the dialog just provide a "shortcut" for entering information into this field.


Many of the bright stars in the sky have a "proper name". For example, the "pole star" is called "Polaris"; the bright red star at Orion's "shoulder" is called "Betelgeuse". The combo-box in the "Proper name" section of this dialog lists all the proper names which SkyMap knows about.


Let's find "Betelgeuse" on the map. Run SkyMap and display the "Find Star" dialog. Click on the "down arrow" at the right side of the proper name combo-box (the box showing "Acamar" in the picture above), and the list will "drop down". Scroll through the list until you find "Betelgeuse" (alternatively, type the first few letters of the word, and Windows will scroll the list to the correct point):



Click on the name "Betelgeuse". The list will close, with the name "Betelgeuse" shown selected. Now click the "+" to the right of the combo-box. The name "Betelgeuse" will be copied into the "Star name" field:



Finally, click the Goto button at the bottom of the dialog. The map will be redrawn centred on the position of Betelgeuse. As with all search operations, the search target marker will show which object has been "found" by the search.


Try searching for other stars with "proper names". You can either use the "+" button alongside the list of names to copy a name to the "Star name" field, or you can directly type the name into the "Star name" field - either will work.


Most stars in the sky don't have a proper name. As you known, the sky is divided into 88 constellations, each constellation occupying a fixed "area" of the sky. The brightest stars in each constellation are labelled with Greek letters, normally called "Bayer Letters" after the man who originally invented this system of labeling stars. As a general rule (to which there are many exceptions!) the brightest star in each constellation is labelled "a" (alpha), the second brightest is labelled "b" (beta), and so on through the Greek alphabet (if you're unfamiliar with the Greek alphabet, it's shown in full in one of the appendices at the end of this manual).


Let's now see how to find a star which is labelled with a Greek letter. We'll search for "a Orionis", which is another name for Betelgeuse. Display the "Find star" dialog as before. This time, we have to enter two items of information; the Greek letter, and the constellation. To enter the Greek letter, click the list in the "Bayer letter" section of the dialog, select "a" from the list, then click the "+" button alongside the list. The letters "alp" will appear in the Star name field (SkyMap uses the first three letters of the "English" version of the Greek letter):



Next, go to the "Constellation" section of the dialog, select "Orion" from the list, and click the "+" button alongside the list. The letters "Ori" (the standard 3-letter abbreviation for the constellation of Orion) will be added to the text in the Star name field:



Finally, click the Goto button. The map (if it is not already doing so) will be redrawn, centred on Betelgeuse.


The final common method of referring to stars is to use their "Flamsteed numbers". Flamsteed numbers are typically used for those relatively bright stars in each constellation which don't have a Greek letter associated with them. Let's search for the star "61 Cygni", which is one of the closest stars to our solar system.


Run SkyMap, and select view level 4; this is the level at which, by default, Flamsteed numbers are switched on. Display the "Find star" dialog, and type "61" into the Star name field (there's no "shortcut" method of entering numbers!). Then, exactly as we've already done for Bayer letters, go to the "Constellation" section of the dialog, select "Cygnus" from the list, and press the "+" button; the letters "Cyg" (the abbreviation for "Cygnus" will be added to the star name field:



Finally, click the Goto button, and the map will be redrawn, centred on 61 Cygni:





We've now covered the basic operation of SkyMap, and you should be in a good position to carry on "exploring" by yourself. The on-line help system describes what the program can do, but don't forget that all the "in depth" help on individual dialogs and menu items is in the "context sensitive" help. To get detailed information about a dialog, press the F1 key while the dialog is visible on the screen; to get detailed information about a menu item or toolbar button, click the {bmc bm0.png]] toolbar button and then click the menu item or button you require help on.

至此我们就讲完了SkyMap的基本操作,你应该可以自如的浏览了。在线帮助系统会告诉你这个程序能做些什么,不要忘了,存在于单独对话框和菜单栏中的“深度”帮助会提供更多的信息。。要查看对话框的详细信息,就在对话框出现在屏幕中时按F1。如果需要菜单栏或工具栏的详细说明,点击 工具栏按钮,然后单击需要解释的菜单栏或按钮。

We hope that you enjoy using SkyMap. Don't forget that information about the program, together with lots of "extras" to enhance it are available from the SkyMap Software web site at http://www.skymap.com.