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Target Component Editor
The detailed component editor containing the target list for an observation is accessed in the usual manner, by selecting the target component in your science program, and is shown below:
In normal circumstances, the target name, co-ordinates and system corresponding to the base pointing position of the telescope will have been extracted from the Phase I proposal and shown in the top panel. The coordinates can be refined by editing the RA/Dec boxes in the Target Environment panel or by dragging the base position in the position editor graphical display.
The target name should contain alphanumeric symbols and blank spaces only, as some other symbols (e.g., brackets) can be interpreted as commands by the observing system.
If the observation is of a new target, the observation element is created with an empty telescope targets component and the science program viewer displays a placeholder (RA: 00:00:00.00 Dec:00:00:00.0 HMS Deg (J2000)) until an object name is given. When online, target coordinates, including proper motions, can be obtained by querying either the Simbad or NED databases. Select the query from the menu indicated with the "down" arrow (see figure above), enter the catalog name of the target in the Name box, and then either press Return or click on the Resolve (magnifying glass) button.
Target brightness information is entered in the middle panel. In Observing Tools prior to 2010B (June 2010), target brightness information was entered into a text box to the right of the coordinate boxes. Any information entered in the old format is shown at the bottom of the window. This information can be deleted by clicking the red X to the left of the string. Starting with the 2012B OT the target brightnesses are entered as value:bandpass:system triples (see figure above). To manually enter a new brightness, select the bandpass from the pulldown menu to the right of the box labeled "Select" and then enter a value into the box. Additional entries to the table can be added by clicking on the green + below the list. An entry can be deleted by clicking on the appropriate red X. The Brightness table is automatically sorted by wavelength.
Adjustments to the pointing position, e.g. for proper motion and tracking at specific wavelengths, can also be made in the middle panel. The default is to track at a wavelength defined by the filter or specified dispersing element in the instrument with no proper motion corrections. Proper motions in milli-arcsec/year can be entered into the boxes. These are also filled in automatically after some Simbad and guide star searches.
Additional information that affects the tracking can be entered in the Tracking Details tab. Click on the "Tracking Details" button on the right edge of the middle panel to open and close this tab. In the vast majority of cases these settings should be left at their default values.
The upper panel displays the target list. Each position has a tag associating it with the base (telescope) or one of the wavefront sensors (WFSs). The specific WFS tags are associated with telescope offset positions using the offset iterator. The User tag is not associated with a WFS and is normally used to give the coordinates of stars to be used for peak-up before blind-offsetting to a faint target. If you wish to change the tag type for a particular position, select the item in the target list and choose the new tag type from the pull-down list in the middle panel. The distance between the base position and the other targets is listed in arcminutes, and all of the known magnitudes are listed for each target.
Note: the only supported sidereal coordinate system is J2000!
You can add or remove items in the target list (except the base position) using the add/remove/duplicate buttons. Pausing the cursor over one of the buttons will reveal adescription of the button's function. A summary of the buttons is given below.
|Add new empty target or magnitude|
|Remove selected target or magnitude|
|Copy selected target to buffer|
|Paste target buffer into selected target|
|Duplicate selected target|
|Activate/deactivate selected guide star|
Targets can be copy/pasted between target components in different observations, including observations in different programs.
The Duplicate button will copy the information of the selected target and copy it toa new line in the table. If the base position is duplicated then the new target has a User tag. If another type of target is duplicated then the new target has the same kind of tag as the original but therunning number is incremented. For example, if target PWFS2 (1) is duplicated then the new target has the tag PWFS2 (2).
Duplication is especially useful for preparing AO observations in which the AO correction is calculated from the science target. In these cases the target and guide star must have the same name and coordinates.Therefore, one can simply duplicate the target and then set the tag for the appropriate type of wavefront sensor. If using Altair then the guide star tag should be AOWFS while if using NICI then the guide star tag is OIWFS.
The Guide with menu is used to change the default WFS used by the automatic guide star algorithm. By default it suggests the most likely guide star needed for the instrument and AO system (if any) in the observation.
The Auto GS button will perform an automatic search for the brightest guide star which is reachable by the guider at all currently defined offset positions.
The Manual GS button will open the position editor (if it is not already open) and then open the Guide Star Selection dialog for doing guide star searches from the standard online catalogs.
For details on observing non-sidereal objects please see the Non-Sidereal Targets page.
Guide Star Quality
The guide star "Quality" provides an estimate of whether the brightness of the guide star could impact the delivered image quality:
|Guide star is bright enough to deliver the requested image quality in the specified conditions|
|Slower guiding required; may not deliver the requested image quality in the specified conditions|
|Slower guiding required; will not deliver the requested image quality in the specified conditions|
|Guide star is very faint; we may not be able to guide in the specified conditions|
|Guide star is too faint (or too bright) to guide in the specified conditions|
The guide star quality details are displayed at the bottom of the Target Environment when the guide star is selected. The limiting magnitudes for the selected wavefront sensor are shown at the right, and hover-over text gives estimates for the different guide speeds (fast, medium, and slow).
The guide star quality is meant to be a guideline only, providing a warning when guide stars may be of inadequate brightness for the requested image quality and observing conditions. In practice, the guide speed and impact on delivered image quality will depend on the accuracy of the guide star catalog magnitude and the specific conditions during the observation.