Working with Exposure Specifications

The Visual Target Tuner allows you to overlay instrument apertures on an image of your target. If you are considering parallel observations, you can also display the rest of Field of View (FOV) for the observatory.

Selecting an Exposure Specification

By clicking on an exposure specification in the hierarchical editor you establish the context from which the VTT will obtain the information it needs. Selecting an exposure and then clicking on the VTT tool icon will make the VTT the active tool. The VTT will use the target coordinates for the target associated with the selected exposure when retrieving an image and it will use the instrument configuration information to determine which aperture to overlay.

Displaying the Field of View

Once you have displayed an aperture on an image, you can investigate parallel observations by toggling on the Field of View ( FOV) for the observatory. Just select "Show Entire FOV" from the "ImageTools" menu or click on the FOV icon in the tool bar. The FOV is then displayed relative to your selected observation. This allows you to easily see where other the apertures would be located given your targeted position, selected aperture and rotation angle.

If you would like a more (or less) detailed FOV overlay, you can modify which apertures are displayed from the "Modify FOV Aperture List" item in the "Image Tools" menu. From here you can choose to display all apertures, turn whole instruments on or off, open the menu for an instrument and choose specific apertures, or return to the "Default" set of apertures. If you have the FOV option on, you will see the parallel apertures come and go as you click in the check boxes.

[Special note for HST NICMOS users: Notice that there are multiple entries for the same camera. The different focus positions change the position in the HST field of view significantly. Be sure when working with parallel NICMOS observations that you choose a consistent set of apertures such as: NIC3, NIC2 (Focus 3), NIC1 (Focus 3).]

Changing the Aperture

To change to a different aperture, edit the exposure specification in the Form Editor or the mini-spreadsheet. Changing the aperture will not change the targeted position.