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Target Component Editor

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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:

target component editor

In normal circumstances, the target name and coordinates will have been extracted from the Phase I proposal, and will be 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 (HH:MM:SS.s) Dec:00:00:00.0 (DD:MM:SS.s) (J2000)) until an object name is given. When online, target coordinates and motion parameters can be obtained by querying the Simbad database by either pressing Return in the Target field, or by clicking on the magnifying glass.

Caution! Note: the only supported coordinate system is J2000!

The scheduling time is used to determine the coordinates of nonsidereal targets, and defaults to the middle of the semester. This field is inactive for sidereal targets.

Target brightness information is entered in the middle panel, and is used as input to the ITC and to determine guide star viability. This information can be deleted by clicking the red X to the left of the string. 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 labelled "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.

Target motion parameters are listed in the box below the coordinates. Proper motions are specified as µαcosδ and µδ, expressed in mas/yr (10–3arcsec/year) along with the epoch of the proper motion. The parallax should be given in mas. The apparent line-of-sight velocity may be specified as either radial velocity (RV in km/s) or redshift (z). Some or all of these parameters may be filled in automatically with Simbad and guide star queries.

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 at the bottom of the top 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 you may need to use the horizontal scroll-bar to see all the values).

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 button Add new empty target or magnitude
Remove button Remove selected target or magnitude
copy button Copy selected target to buffer
Paste button Paste target buffer into selected target
Duplicate button Duplicate selected target
Activate guide star button 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 to a 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 the running 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 whilst, if using NICI then the guide star tag is OIWFS.

The Auto Guide Search menu is used to change the 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 Manual GS button will open the position editor (if it is not already open) and then open the Catalog Query Tool for doing manual guide star searches from either the UCAC4 or PPMXL catalogs.

Non-Sidereal Targets

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:

100% Guide star is bright enough to deliver the requested image quality in the specified conditions
75% Slower guiding required; may not deliver the requested image quality in the specified conditions
50% Slower guiding required; will not deliver the requested image quality in the specified conditions
25% Guide star is very faint; we may not be able to guide in the specified conditions
0% 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.

Source Parameters

Since 2015B, the OT includes an interface to the Integration Time Calculators (ITCs), which requires specifying the source morphology and spectral energy distribution. These may be set in the Source panel to the right of the Magnitudes panel. Note that you may need to expand the OT window horizontally to see the Source panel:

Target Environment Source Editor Spatial Profile choices
Spectral Distribution choices

The source Spatial Profile may be one of:

  • Point Source, where the integrated brightness is specified by the magnitude table
  • Extended Gaussian source, which will reveal a field to specify the FWHM in arcseconds, and the magnitude table describes the integrated brightness
  • Extended Uniform Source, where the magnitude table describes the surface brightness in magnitudes per square arcsecond

The source Spectral Distribution may be one of:

  • Library Star, which reveals a drop-down list of stellar templates
  • Library Non-Star, which reveals a drop-down list of SED templates, including: Elliptical Galaxy, Spiral Galaxy, QSO, HII Region, Planetary Nebula, etc.
  • Black Body, which will reveal a field to enter the source temperature in Kelvin
  • Emission Line, which will reveal 4 fields: Line Wavelength (microns), Line Width (km/s), Line flux (W/m2), and Continuum flux (W/m2/um)
  • Power Law, which will reveal a field to enter the power-law index
  • User Defined, which will reveal a list of all SED files attached to the OT

Gemini Observatory Participants