Horizon/Telescope Limit Line Editor dialog box (View | Reference Lines, Edit Local button)

Use this dialog box to draw horizon lines and telescope limit lines. The rectangular area represents a portion of the celestial sphere, 0 to 90 altitude along the vertical axis and 0 to 359 degrees azimuth along the horizontal axis (0 degrees is due north). The line drawing control can be used to draw be drawn to resemble your local horizon, and to define telescope altitude and declination limits.

To Draw a Line

1. Move the mouse pointer inside rectangular area. The mouse pointer changes to a pencil.

2. Click and drag the mouse to change the line's shape. Click and drag the right mouse button to draw a straight line between any two points. You can start or end a straight line anywhere with the editing area – the straight line and the existing curve are connected when you release the mouse button.

The caption of the dialog shows the name of the horizon/limit line file you are editing and the type of the line:

• Local – Local Horizon line.

• Altitude – Altitude Limit line.

• Declination – Declination Limit line.

Local Horizons

If you want to create a line that best replicates the horizon from your location, start by looking North and estimating the altitude of objects that you see as you rotate Eastward. Once you have drawn the "first draft" of your local horizon, refine it by using your telescope to look at small sections of the horizon and compute the altitude and shape of objects at given azimuths.

If you want a really accurate local horizon, you can use your computer-controlled telescope to map out the local horizon line using TheSky and the telescope interface. See the Horizon Editor command under the Telescope menu for more information on how to do this.

Telescope Altitude and Declination Limit Lines

Due to limitations in telescope mounting hardware, you may wish to define regions of the sky that a computer-controlled telescope cannot slew. Do so by defining altitude limit and declination limit lines with the Horizon Line Editor.

For example, suppose your fork-mounted, computer-driven, equatorial telescope cannot slew to declinations above 70 degrees. You can define a declination limit line at 70 degrees. During a telescope link session, if you have the Impose slew limits option checked under the Telescope Setup dialog box, TheSky will warn you if you attempt to slew to an area of the sky above 70 degrees declination.

Open

Load a Sky Horizon that is stored on disk.

Save

Saves the current Sky Horizon.

Save As

Saves the current Sky Horizon with the name you supply.

Copy

Copies the points of the current line to the Clipboard.

Paste

Pastes a Horizon line from the Clipboard to the Editor window.

The horizon line is copied to/pasted from the Windows Clipboard as "360-row by 1-column" text data. Each line represents one degree in the 360-degree horizon. The corresponding numerical value represents the altitude at that position.

You can copy/paste this data to/from your favorite spreadsheet software.

Altitude

Displays the current altitude of the drawing pencil icon for Local and Azimuth Limit Horizons.

Azimuth

Displays the current azimuth of the drawing pencil icon for Local and Azimuth Limit Horizons.

Declination

Displays the current declination of the drawing pencil icon for Declination Limit Horizons.

Right Ascension (degrees)

Displays the current right ascension of the drawing pencil icon for Declination Limit Horizons.

Match Horizon Image

Use this button to automatically generate a Local Horizon Line that matches the current Real Mode Options photographic horizon.