Reading off the Right Ascension and Declination

It is straightforward to read off the approximate Right Ascension and Declination of any object in the image.

1. The $x,y$ pixel positions and the Right Ascension and Declination of the current cursor position are shown in the boxes labelled: X:, Y:, $\alpha$: and $\delta$: in the control panel in the middle of the upper portion of the main window. To find the approximate coordinates of a star simply position the cursor over it and read them off.

2. In a DSS image J2000 equatorial coordinates are shown by default. It is possible to configure GAIA to display other celestial coordinates. Click on the Image-Analysis button in the menu-bar along the top of the main window and choose Change coordinates and then Celestial coordinates....

   A window appears which allows you to specify the coordinate system. Choose the one required (perhaps ecliptic coordinates) and then click the Accept button.

   Henceforth coordinates are displayed in the chosen system (but note that the coordinate boxes are still labelled `$\alpha$:' and `$\delta$:', even if ecliptic or Galactic coordinates have been selected).

   Also, the coordinates are only updated when the cursor moves. Thus, if it is already positioned over the star that you are interested in, then you need to nudge it off the object and return it to the required position.

3. Depressing the Caps Lock key will prevent the $x,y$ and $\alpha$,$\delta$ values being updated as the cursor moves. This facility is useful, for example, if you wish to preserve the coordinates whilst moving the cursor to another window.

4. A list of positions in an image can be selected and saved as a text file by selecting the Positions... item from the Image-Analysis menu (in the menu-bar along the top of the main window).