Define Fields dialog box (Data | Export, Define Fields button)

 

Use this dialog box to define database fields in a text file. The contents of the text file that was specified in the Import dialog box is displayed at the bottom of the window.

 

Entering Field Information

Before a Sky Database (SDB) can be created from a text file, the location of the database fields (right ascension, declination, magnitude, etc.) in the text file must be specified by marking the starting and ending columns for each field. To do this, highlight the columns for a given field by clicking and dragging the mouse, then click the corresponding button on the upper portion of the dialog box.

 

For example, to set the RA Hours field, highlight the columns in the text file that hold the right ascension hours information, then click the RA Hours button. Once the column selection is made, vertical gray lines show the defined field positions.

 

The first 80 lines of the text file are shown in the text file window. These text lines provide a visual reference to the data you are parsing and can be used as a reference when setting the field information. The tedious and error prone task of entering the starting and ending columns for database fields is simplified using the visual feedback from this text window.

 

Highlighting a Database Field

A database field can be highlighted using one of the following methods:

 

To enter the field information

  1. Highlight the coordinates (RA/Dec or altitude/azimuth) in the text file window as described above.

  2. Click the button on the upper part of the Field Definition dialog box that corresponds to the highlighted data.

  3. Repeat steps 1 and 2 for each required data field.

  4. For each additional field you wish to have appear in the Object Information dialog box when the Sky Database is queried, highlight the columns, choose one of the available buttons (1-8), then enter a description for the field.

 

To clear column information for a field make sure nothing is highlighted in the text area (the column selection text box will show 0-0) then click the button corresponding to the data field you wish to clear.

 

If you wish to see which columns are associated with a particular field, press and hold the Shift key while clicking on the button in question. The column’s selection for that button are displayed in the text window and shown in the Column Selection edit box.

 

Required

The options in this group must be defined before creating a Sky Database file.

 

RA Hours

Click this button after the columns that hold the right ascension hours coordinate data have been selected. If the RA hours are in decimal form, the entire number should be highlighted (RA minutes and RA seconds are not used). If the Horizon-based Coordinates option is marked in the Import dialog box, this button is labeled "Azm Deg" and corresponds to the azimuth degrees.

 

RA Mins

Click this button after the columns that hold the right ascension minute’s coordinate data have been highlighted as described above in Highlighting a Field. If the RA minutes are in decimal form, the entire number should be highlighted and the input button for RA seconds will not be used. If the Horizon-based Coordinates option is marked in the Import dialog box, this button corresponds to minutes of azimuth and is labeled as such.

 

RA Secs

Click this button after the columns that hold the right ascension seconds coordinate data have been highlighted as described above in Highlighting a Field. If the Horizon-based Coordinates option is marked in the Import dialog box, this button corresponds to the azimuth seconds and will be labeled as such.

 

Dec Sign

Click this button after the columns that hold the sign (+ for North, - for South) of the declination coordinate data have been highlighted as described above in Highlighting a Field.

 

Dec Degs

Click this button after the columns that hold the Declination degrees coordinate data have been highlighted as described above in Highlighting a Field. If the Declination degrees are in decimal form, the entire number should be highlighted and the following two inputs (Dec minutes and Dec seconds) will not be used. If the Horizon-based Coordinates option is marked in the Import dialog box, this button corresponds to the altitude degrees and will be labeled as such.

 

Dec Mins

Click this button after the columns that hold the Declination minutes coordinate data have been highlighted as described above in Highlighting a Field. If the Declination minutes are in decimal form, the entire number should be highlighted and the following input (Dec seconds) will not be used. If the Horizon-based Coordinates option is marked in the Import dialog box, this button corresponds to the Altitude minutes and will be labeled as such.

 

Dec Secs

Click this button after the columns that hold the Declination minutes coordinate data have been highlighted as described above in Highlighting a Field. If horizon coordinates were selected in the Import dialog box, this button corresponds to the Altitude seconds and will be labeled as such.

 

Optional Fields

The following fields may or may not be required to achieve the expected behavior from a Sky Database. Some of the fields will be grayed depending on the Class of the database.

 

Magnitude

Click this button after the columns that hold the magnitude data have been highlighted as described above in Highlighting a Field. Only databases that are of type Star will use this magnitude field to plot the various magnitudes with relative brightness.

 

Alias

Click this button after the columns that hold the Alias identifier have been highlighted as described above in Highlighting a Field. Object aliases are alternate names for an object. TheSky uses this information to perform cross references when a query is performed on the object using the Find command.

 

The use of the alias field partly depends on the Class of the database. In all cases, the alias is expected to be in the resident databases of TheSky and not in other SDBs. The resident databases include the Guide Star Catalog, the Hipparcos, Tycho and SAO star catalogs, the NGC, IC deep sky catalogs. TheSky Level Professional Edition also includes the complete PGC galaxy catalog, PK planetaries, the GCVS and NSV variable star catalogs.

 

Alias use in Class Objects/Points

If the Sky Database is of type Objects/Points, the alias is used to set up a cross reference between the object in the SDB and the corresponding object that is part of the resident sky data. For example, most of the objects in the Caldwell catalog created by Patrick Moore have a corresponding NGC number. When the Caldwell database is loaded, you can perform queries on either the NGC object or the corresponding Caldwell number. The information for both entries are combined in the Object Information Dialog since the SDB uses the Alias field for cross referencing.

 

Alias Use in Class Labels

If the Sky Database is of type Labels, the alias is used to display the label associated with the alias object in the Object Information dialog box. For example, when you use the Find command on the star SAO 113271, each of the resident SDBs is searched for an alias of SAO 113271. The common star name database contains an entry for the star Betelgeuse, which has an alias of SAO 113271, and is found during this search. This allows TheSky to display the name Betelgeuse in the Object Information dialog box, even though its SAO number was used to find the object.

 

Alias Use in Class Lines/Polygons

Sky Databases of this class do not use the Alias button.

 

Find

Click this button after highlighting the columns that define the field to be searched when the SDB is selected from the Find dialog box. Only SDBs that have the search field defined can be queried. Also, the Find dialog box will list each SDB in the Databases group list box that has a search field. The search is performed by typing the identifier of the SDB followed by the text you are looking for. For example, if the unique identifier for a database is CALDWELL, and you are looking for an object in this database named NGC1976, enter CALDWELL NGC1976 into the Find text box.

 

Label

Click this button after highlighting the columns that hold the Labeling text. This text will appear on the Virtual Sky. It will also appear in the Common Names list box in the Find dialog box when the SDB is highlighted in the list.

 

Obj. Type

Click this button after the columns have been highlighted which contain information about the type of object on the corresponding database text line. This function is only used when the SDB you are compiling contains multiple object types and you wish to have TheSky determine the object types from the text in the field. See Advanced Compile Options dialog box for more information.

 

Maj. Axis

Click this button after the columns have been highlighted which contain the major axis of the object in arc-minutes. If the major axis and minor axis of an object are specified, the object will show extent once the Virtual Sky has reached a high enough magnification. If the major axis is specified on the text file in units other than arc-minutes, the Advanced Compile Options dialog contains an entry for applying a multiplication factor to the field.

 

Min. Axis

Click this button after the columns that contain the minor axis of the object in arc-minutes have been highlighted. If the major axis and minor axis of an object are specified, the object will show extent once the Virtual Sky has reached a high enough magnification. If the minor axis is specified on the text file in units other than arc-minutes, the Advanced Compile Options dialog contains an entry for applying a multiplication factor to the field.

 

Position Angle

Click this button after the columns that contain the position angles of the object in degrees have been highlighted. The position angle is measured from North in a counter-clockwise fashion and should always be between zero and 180 degrees. If the major axis is specified on the text file in units other than arc-minutes, the Advanced Compile Options dialog box contains an entry for applying a multiplication factor the field.

 

Column Selection

You can manually enter the starting and ending columns of a field in the text file as an alternative to using the mouse using the Column Selection edit box. Enter the starting and ending columns separated by a dash (-), then click the corresponding button.

 

User Fields

In addition to the data used to plot the objects from a Sky Database on the screen, there are eight "user fields" that can be used to display other pertinent information from the text file database. Highlight the additional field as described in Highlighting Fields above, then click one of the buttons numbered 1 through 8. When the Object Information dialog box lists information on the object, the text entered in the edit box will appear, followed by the text file information from the highlighted fields.

 

For example, given that a text file database has a description field that contains interesting information about each object, one of the user fields could be used to list this description in the Object Information dialog box. Do this by highlighting the field in the text window, clicking the button labeled 1, then typing in the text "Description" in the corresponding edit box.

 

Advanced

This button displays the Advanced Compile Options dialog box. It is used for object type determination and applying multiplication factors to some of the numeric fields contained in the source text file.

 

Object Type Determination

Object Type Determination is used when more than one type of object is present in a text file and you wish to compile the text file into an SDB having multiple types. Normally, the Object Type is specified on the Import dialog box and it applies to all objects in the database.

 

Object Type Determination is best explained with an example. The following text file has three entries, two galaxies and an open cluster:

 

Gal 00 40.4 +41 41 8.1 NGC 205 H V 18

Gal 01 09.5 +35 43 10.1 NGC 404 H II 224

OC 01 57.8 +37 41 5.6 NGC 752 H VII 32

 

To create an SDB that contains the three objects and plots both galaxies and open clusters, the Object Type columns must be set in the Field Definition dialog box to columns 1 through 3. Next, in the Advanced Compile Options dialog box, enter the strings that indicate the type galaxy and the type open cluster. In this example, select Galaxy from the list box on the left, then type in Gal in the edit box on the right. Do the same for Open Cluster and enter "OC".

 

Once this is entered, the database compiler searches for the string "Gal" in the columns specified with the Object Type button on the Field Definition dialog box. If "Gal" is present in the columns, the object will become type Galaxy (or whatever object type is specified).

 

Up to eight different types can be present in a single Sky Database.

 

Text File Display

The text box at the bottom of this dialog box shows the contents of the text file that was selected in the Import dialog box. Use this text box to specify where the field information resides within the text file.