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This module sets filter criteria for [node3.html#dso_selection Object Selection] (Figure [#fig:select_search_type_screen 10]). There are two ways to search for objects - Primary and SQL-like. The first one provides with a special screen where one selects a number of parameters to search by whereas the second uses logical expression for the search.
Internal catalogs may contain same objects with different names, to make sure that search result does not contain the same object several times turn [#exclude_dups Exclude duplicates] option on.
Select object catalogs
Select object catalogs for a search among all [node1.html#object_internal_databases internal object databases] and user catalogs
Select search type
Select either Primary search or SQL-like search.
- Select object types. Use this for selecting [node15.html#object_types object types]
- Empty field treatment. For incomplete data sets, when some of the object's data values are missing, you can select the preferred way to resolve the situation during search (i.e. treat the empty field as zero valued, as a ''very large number'' or regardless count it as a positive or a negative match)
- Primary search parameters
- Filter type. Select a filter or do not use it at all
- Visibility Filter. Objects above or equal to a [node15.html#object_vis detection limit] are looked for
- Maximum magnitude filter. Objects with a magnitude below or equal to a specified value are looked for.
- No filter. No filter is applied
- Select constellation. Select one or several constellations to search objects in. If no constellation is selected, objects are searched in all constellations
- Object name starts with. Select the beginning of the object name. This option is convenient for catalogs combined from various sources like SAC. As an example, by setting name beginning to ''cr'' you limit your search to Collinder open clusters
- Object minimal size. Search for objects with the dimension above or equal to the specified one
- Lowest altitude. Search for objects which rise above the specified altitude during observation time range
- Detection limit. Set the [node15.html#object_vis threshold] for the visibility filter
- Set maximum magnitude. Set the threshold for maximum magnitude filter
- Minimum separation. Minimum separation between components when searching in double star catalogs
- Maximum separation. Maximum separation between components when searching in double star catalogs
- Maximum mag2. Maximum magnitude of the second component when searching in double star catalogs
- Filter type. Select a filter or do not use it at all
This module contains a list of SQL-like expressions defined by user. Select one to use for a search. Initially the list contains 3 simple basic expressions as examples. Create a new search request with Add new search request button at the bottom of the screen.
SQL-like expression consists of two parts:
- SQL request. The request is used to search any database by its non-calculated fields
- Local request. The request is used to filter by calculated values: altitude and visibility
The following fields could be used in expression (in any case - upper-case, lower-case or mixed).
- TYPE. Object type. Could take the standard [node15.html#object_types object type] value
- A. Larger object dimension in minutes
- B. Smaller object dimension in minutes
- RA. Right ascension (2000) in hours
- DEC. Declination (2000) in degrees
- MAG. Magnitude
- PA. Position angle
- CON. Constellation (3 symbol Latin abbreviation)
- ALT. Minimal altitude
- VIS. [node15.html#object_vis Visibility] from 0 to 5
The following operations could be used in expressions
- $a=b$ - a is equal to b
- $a>b$ - a is greater than b
- $a<b$ - a is less than b
- $a\char93 b$ - a is not equal to b
- $a\&b$ - logical AND (e.g. $(mag>12)\& (type=GC)$ - object magnitude is higher than 12 and its type is equal to GC)
- $a\vert b$ - logical OR (e.g. $(type=GC)\vert(type=OC)$ - object is either GC or OC
Examples of SQL request
- $(a>15)\& (con=and)$. All objects from Andromeda constellation with larger axis above 15 minutes
- $a>10\& type=gc$. All globular clusters larger than 10 minutes
- $a>7*b \& a>10 \&type=gx$. Edge-On galaxies
- $id>0$. All objects in database
Example of Local request
- $alt>20$. Objects that have an altitude above 20 degrees at least once during the observation period
- $vis>1$. Objects with [node15.html#object_vis visibility] higher than 1
- $alt>20\& vis>1$. Both above conditions should hold
- Edit. Edit the selected expression
- Remove. Remove it from the list
Provides standard [node15.html#import_export export/import] operations.
This part allows to set conditions common to both Primary and SQL-like search.
- Exclude duplicates. This is an option to remove physically duplicated objects when searching in intersecting databases with the same/different object name notations. As an example, if you select NgcIc and UGC catalogs and turn this option on, then among galaxies NGC2 and UGC59 (which are the same) only NGC2 will be found. Without this option the application finds both NGC2 and UGC59. This feature also excludes duplicated objects from the same catalog (e.g. NGC6/NGC20, NGC17/NGC34)
- Time of observation. Set observation range. In addition to setting the time range manually, one may easily define the ranges with a reference to astro twilight, sun rise and sun setting
- Telescope/Instrument. Select an [node11.html#telescope_list instrument] for observations
- Geographic Location. Select [node6.html#geo_location observatory location]
- Sky limiting magnitude. The magnitude of faintest stars at zenith. Used for visibility calculations