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Tips, Bugs and Troubleshooting

Some hints for successful use of GMMPS. Go directly to:


Running GMMPS 

  • Do not run the GMMPS in the background if displaying it from a remote host. If the connection to the host fails, or other similar problems arise, then unusual errors occur in Skycat. It is safer/easier to just run the software in the foreground.
  • At the bottom of each of the Skycat windows there is a grey information icon. This displays additional information about the function of the button/window that the cursor is pointing to.
  • Do not use an Object Table with an extra "." in its name. This confuses the software such that when it attempts to append the "ODF" to the file name when the mask is created.

Image Display 

  • When the image is first displayed, the intensity levels are usually not automatically set correctly. To adjust the color scale of the image, go to "View - Cut levels" on the main menu. This will open a window in which it is possible to adjust the intensity levels of the pixels. For instance, if the intensity level is too low, then to increase the level, change the "Auto set" from 100% to 98%. This changes the fraction of pixels that are within the cut levels. Then close the pop-up window as desired. Also, one could use the "low" and "high" rectangle at the bottom of the right panel (above the "Auto Set Cut Levels" button).
  • To zoom-in on the image, click on the large "Z" button to the bottom-left of the screen. Similarly, to zoom out of the image, click on the small "z" button.
  • To clear the slits from the image, click the "Clear Slits" button in an ODF catalog window with the blue menu bar. This is the only way to clear the slits.
  • To clear the symbols from the image, click the "Clear Symbols" button from an OT catalog window with the red menu bar.  You may also go to the main menu of the Skycat window and select "Graphics - Clear". This WILL NOT, however, clear the slits from the image.
  • To clear the image and all graphics, in the main menu of the Skycat window, select "File - Clear".

Object Management 

  • To force the algorithm to choose objects that are required in the mask, it is often useful to ignore lower-priority objects (priority "Ignore Object" or X) if they are preventing higher-priority objects from being selected.
  • Do not manually edit the catalog file (*.cat) - always manipulate the FITS Object Table file; e.g. mask_OT.fits. Manipulating the .cat files can easily make them invalid, with the changes not being translated into the minimal ODF files. These are simply temporary files.
  • Remember that the mask making software starts to assign objects based on a specific algorithm. Care should be exercised to make sure that objects are chosen as the user wants them chosen.
  • The software does check to see that sufficient valid acquisition objects have been chosen and will give a warning in the mask design window (gmmps_spoc) if there are less than 2 acquisition objects in the mask. However, it will not prevent the creation of these mask designs. A submitted mask design WILL NOT PASS THE GEMINI CHECKS if less than 2 acquisition objects are selected clear of the GMOS CCD gaps. Gemini cannot accept masks with less than 2 acquisition objects, since these are required to align the mask on the sky.



  • There are currently no known bugs in v0.402.
  • 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 here).  
  • The search functionality in v0.30X, with columns set through "Options -- Set Search Columns..." does not work correctly.
  • The slit placing algorithm in v0.30X does not correctly place priority 2 and 3 objects close to acquisition objects. If you have trouble getting the software to place a priority 2 or 3 object close to an acquisition object, try changing its priority to 1.



  • After you have selected "Make Mask Files" and the window showing the division of objects into the masks appears, you may observe that a lot of text appears in the pop-up window that appears, similar to below (see the writing starting from Acq Object...). This tells you that there are too many acquisition objects selected. Go back to catalog window and ensure that the number of acquisition objects is less than 10.

    [Error window]
  • If you find after loading the Object Table, that the symbols are not overlaid over the displayed image, it is probably because the Object Table (e.g. mask_OT.fits) does not match the image file.
  • When in doubt...exit Skycat and then start the software again.


Last update June 5, 2013; Mischa Schirmer and Bryan Miller
In original form February 10, 2003; Dione Scheltus

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