- Gemini Home
- Telescopes and Sites
- Science Visitors at Gemini
- Observing With Gemini
- Status and Availability
- Nod and Shuffle
- Spectroscopy Overview
- Long-slit Spectroscopy
- Multi-Object Spectroscopy
- Mask Prep. Intro
- Mask Design
- Mask-making Software
- Mask Checking
- Mask Deadlines
- Observing Strategies
- Integral Field Spectroscopy
- ITC, Sensitivity and Overheads
- Guiding Options
- Observation Preparation
- Data Format and Reduction
- Visiting Instrument Policy
- DSSI Speckle Camera (North)
- TEXES (North)
- Integration Time Calculators
- Adaptive Optics
- Magnitudes and Fluxes
- Near-IR Resources
- Mid-IR Resources
- Observing Condition Constraints
- Performance Monitoring
- SV/Demo Science
- Future Instrumentation
- Queue and Schedules
- Data and Results
Change page style:
Editing and Prioritizing
This page contains instructions on editing slit and object properties and assigning priorities to objects. Go directly to:
The colored symbols overlaid on top of the image represent the priority levels of the objects listed in the catalog window. A handy feature of the catalog window is that by double clicking on an object's parameters in the catalog, a label will appear on the image next to that object. Towards the bottom of the catalog window, the message "labeled object xxx in image" will appear, where xxx is the object's ID number.
The objects in the Object Table need to be prioritized. There are five priority levels: Priority 0 (Acquisition Object), Priority 1, 2, 3 and Ignore Object.
Acquisition Objects are used to align the mask on the sky. Priority 1 objects are ones that you wish to observe. Priority 2 and 3 objects are potentially interesting objects, however at this time slits for this object are less important (`Priority 3' objects are less important than `Priority 2' objects). Objects that you want to keep in the Object Table but not have considered at this point may be labelled `Ignore Object'. You may want to use these objects later to fill unused space in a mask designed to contain as many as you important objects as possible.
Each of these priority levels corresponds to a different symbol as follows:
In the catalog window:
- Single or multiple rows may be flagged at once. To change the priority of a single object, simply highlight (click) on the object and click on the appropriate priority button: "Acq. Object, P0", "Priority 1", "Priority 2", "Priority 3".
- To change the priority of multiple objects, either press "Shift-Click" for a block of successive objects in the catalog listing, or press "Ctrl-Click" for non-successive objects. Then click on the appropriate priority button.
- To change the priority of every object in the catalog, it is often easier to use IRAF. This is outlined below.
- To cancel a flagged object, select it and click on "Ignore Object". It will then be marked with a yellow cross on the image display.
Only objects that appear in the catalog table (i.e. are represented on the image by some symbol) may be selected and therefore masked.
NOTE: A minimum of two acquisition objects are required for the mask alignment. A maximum of 10 are allowed. It is recommended to use 2-4 acquisition objects.Make sure none of these are in the gaps between the CCDs. You can show the gaps by clicking "Plot GMOS gaps" on the catalog window.
A bug in GMMPS v0.304 will prevent changes to the priorities unless the column "slittilt" is present in the object table. You can add the slittilt column using the IRAF tasks app2objt, stsdas2objt (see here), or tcalc (see below).
Slit sizes and tilts
To adjust the size and position of the slits, simply:
- Click on the required object(s).
- Enter the new parameter in the boxes adjacent to the parameter listings e.g. Slit Size Y, Slit Tilt etc.
- Either hit "Enter", or click on "Update Row" and the value for the object will be changed. Note that it does take a couple of seconds to update the row. Thus if multiple parameters are being changed, it's easier to enter all the values in the boxes and then click "Update Row", rather than pressing "Enter" after each individual parameter value is altered.
It is possible to have tilted slits. However your FITS Object Table must contain the slittilt column before you load it into the mask design software.
Searching the Object Table
This functionality currently does not work correctly.
Editing an object
To edit any column values for an object:
It is easiest to use IRAF when creating the Object Table, or when you wish to add a column or change a certain column value for the whole Object Table.
To print the table in IRAF, type tprint mask_OT.fits . You can also use tread mask_OT.fits. Using tread, you can scroll across to see all columns, however, you can not alter values using this tool. To exit tread, hit Ctrl,D then type quit. For help, hit Ctrl,D and then type help.
To only list the column names of the Object Table, use the task tlcol, e.g. tlcol mask_OT.fits will list the names of the columns for that FITS file.
The task tcalc performs arithmetic operations on table columns. Using this, you can add columns, or alter a column and output the result into new column.For more information about the table editing tools contained in IRAF, type help ttools. Most of the tools in this package may be useful in editing or creating new Object Tables.
Last update June 26, 2011; Bryan Miller
In original form February 10, 2003; Dione Scheltus