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### A.5.8 Sky Plot Window

Sky Plot Window

The Sky Plot () plots longitude/latitude positions onto the celestial sphere. It can plot to a number of projections (currently Sin, Aitoff and Plate Carrée). See the Window Overview for features common to all layer plots.

The positional coordinates are Longitude and Latitude, specified in degrees. When supplying them, you can specify an associated Data Sky System (Equatorial, Galactic, Supergalactic or Ecliptic2000). Note that this is the sky system of the data coordinates, not (necessarily) of the plot you want to see. To specify the coordinates you want the data to be plotted on, use the View Sky System option in the Projection tab of the Axes control. However, if you just want to view the data using the same system as the coordinates you are supplying, you can ignore leave these values as their default (both Equatorial) and no conversion will be done.

Navigation controls:

Panning
  The Sin projection is like the surface of a globe that can be rotated by dragging it around, while the Aitoff and Plate Carée projections are like maps drawn on a piece of paper which can be dragged around. In all cases, drag by holding the left mouse button.

  Dragging will attempt to keep the same sky position under the cursor. This is usually possible, but in the Sin projection if the mouse starts off on the sphere and moves off it, that can't happen, so the panning can be jerky in that case. This only happens at low magnifications.

Zooming
  The best way to zoom is using the mouse wheel on the plot (some machines with no wheel can simulate this with a two-fingered slide on the mouse pad), since this zooms around the current mouse position. An alternative is to use the zoom buttons (/) on the toolbar, which zoom around the center of the plot.

  In the Sin projection, the zoom will rotate the sphere as well as increase its magnification, so that the cursor can stay on the same sky position while north remains pointing upwards.

The sky plot offers the following plot controls:

- Table Layer Control, with these form options:
  - Mark
  - Size
  - Vector
  - Ellipse
  - Text Label
  - Contour

The Axes control () is described in the next subsection.

- A.5.8.1 Sky Axes Control

Next Previous Up Contents
Next: Sky Axes Control
Up: Layer Plot Windows
Previous: Plane Axes Control

TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk