Science Operations

Mask Preparation

LUCI MOS Mask Preparation with LMS

These pages serve to guide the users through generating a MOS mask for LUCI, focusing on the functions and features used in the new Version 3.1.2 of LMS.  The major updates to LMS include:

Alignment stars can be placed without cut boxes

Auto-slit available at all position angles

Updated menus to help guide the user through the optimal mask configurationUpdated more accurate scale factor

Fully backwards compatible with previous LMS releases 

Please Note:  Any masks previously designed with v1.65 can be imported into 3.1.2 and either saved in the new version or  updated.  v1.65 is no longer supported

The steps for successful mask generation are:

The linked pages will guide you through each step of the process.  Many features described in the linked pages are specific to version 3.1.2 so we recommend you upgrade to this before proceeding with mask development.

Additional tips and troubleshooting hints can be found on the LMS Troubleshooting tips page.

Mask Preparation with LMS

For all submissions remember the following:

    1. Send the Gerber (.gbr) and lms (.lms) files to your Partner Coordinator. The Partner Coordinator will forward these files to
    2. Please use as many reference stars as possible.
    3. Please check if your reference stars have proper motions:
      • If you are using your own fits images to design masks, it may be useful to compare them with DSS or older images to check if stars have moved.
      • One could load an image or the field center coordinates into DS9.  Then search catalogs (e.g. GAIA, GSC, UCAC, etc) for stars in the field and if there are known proper motion values for the stars.
      • LMS (and MMS) do not accept proper motion updates, you will have to manually update your coordinates with proper motions.
    4. If you are reusing masks that have already been cut in previous semesters, please provide us with the following information:
      • The mask ID.
      • The name of the LMS file. For LUCI programs, please resend the LMS files.
      • PI name or mask name used.
    5. Slit Separations:
      We routinely receive mask designs with slits packed way too close together, either in the vertical direction, or sometimes in both vertical and horizontal directions. As a rule of thumb, please keep any space between slits (and reference stars) to no less than 1.8 millimeters (about 3”). If slits are too close, you risk losing the bridge between them and creating a very strangely shaped slit. This also poses a risk to the instrument.  If you think it looks too close, it probably is too close. There is a check in the slit verification routine that confirms the radial distance between the ends of slits is greater than this limit so watch for this warning.  If you are still not sure, please contact us (or have your Partner Coordinator contact us) before the deadline so that we can check the masks.
    6. Please make sure not to rename the LMS files to something other than what LMS produces. LMS allows for unique names to be created (i.e. luci2.42.M81Targ1.lms) , there is no need to rename the files. The OT will not properly ingest lms files that have been altered, becoming a problem when generating scripts and can lead to downtime at the telescope.  Double check the name you provide observers matches that of your files!

LUCI is capable of doing duplex MOS observations (i.e. “twinned” – same mask, same position angle for both instruments). This is available on a shared-risk basis. Unless you request otherwise, we will fabricate TWO copies of each mask submitted so that LUCI MOS observations can be done in Duplex mode.

If your mask has special requirements, such as pre-imaging required before creating it, please contact your partner coordinator ASAP so that this may be communicated to LBTO and we can coordinate a timetable on how to proceed.  Please remember that LUCI MOS masks require cryogenic cooling and mask exchanges cannot take place on a nightly basis.

As before, if you or your PIs have questions or concerns, don’t hesitate to drop us a line at