Creating Mosaics with Aladin in Phase I

In Phase I mode, you can determine the basic parameters (number of tiles, telescope orientation) needed to mosaic an extended target; detailed information (such as exact pointing requirements) will be determined in Phase II. For a demonstration using a specific example, see the training movie.

You first need to set the Aladin parameters, which are located at the bottom of the Observation window; see the separate help for a full explanation of all the Aladin parameters. The detector and aperture are already set based on the Instrument Setup (although if you have multiple detectors in an Observation, you will need to select the one you want displayed), so you just need to define the mosaic. The values needed are:

  • Mosaic size (X x Y tiles)
  • Mosaic Tile Overlap - the tile overlap percentage

    To see the positions of the individual tiles, open the Observation and Mosaic Tiles containers.

    Bring up the View in Aladin tool, and load a DSS image. By default, the apertures will be aligned at either ORIENTation=0, or the midpoint of the ORIENTation range specified in the proposal.

    You can change the aperture orientation by grabbing the corner of the aperture and dragging. Note that when you release the aperture, all apertures in the mosaic will rotate to that same orientation (all tiles in a mosaic are locked for orientation or position changes). The ORIENTation value will be displayed in the Aladin Orientation Angle field. You will then need to insert the desired ORIENTation range into the proposal. You can also change the overlap size.

    If you want to add another column or row, just change the Mosaic Size values. If you want to add a single tile, click on the Add Tile button. This will place a new tile at the end of the existing mosaic. To move the tile into position, you need to select "Create POS TARGs" mode in the APT Aladin window (if you don't, moving one tile will move the entire mosaic). After the tile is positioned, you will need to commit the coordinate change to the proposal.

    To delete a single tile, you need to first determine its tile number in the Mosaic Tiles container. You can either select a tile in the APT Tree or the Aladin Tree, which will display that one tile only. Once you have found the bad tile, use the Edit menu to delete the tile.

    Once our mosaic is complete, we need to go back to the Observation form and fill in the number of iterations to reflect the final size of the mosaic.

    Last modified: January 21, 2016.