Navigation: Deep-Sky Planner Help > About Documents > Asteroid Search Document >

Sky Position

Sky Position is used to select objects on a particular star chart, or within a range of horizontal coordinates, or near an equatorial position.

Select Ignore if you want to include objects regardless of sky position. If you want to search using one of the other options, you must uncheck Ignore.

Select On ... Chart to choose an atlas and then specify the chart number in the selected atlas. Some of these options may be disabled if an atlas is turned off in Preferences on the Options menu.

Select Local Horizon Model to include objects that are above the lower local horizon model and below the upper horizon model at the ephemeris time. A local horizon model may be defined for a location and may include a lower model and/or an upper model. If the selected location has no model defined in it, objects are included in the report regardless of sky position.

Select Horizontal Position to enter values into Lowest Alt, Highest Alt, Leftmost Az and Rightmost Az. Note that:

▪0° azimuth may refer to either the north pole or the south pole as determined by Preferences

▪The valid range for altitudes is 0° to 90°, inclusively

▪The valid range for azimuths is 0° to 360°, inclusively (360° azimuth is automatically converted to 0°)

If 0 is entered for Lowest Alt, the search result includes all objects located below Highest Alt at Ephemeris Time. If 0 is entered for Highest Alt, the search result includes all objects located above Lowest Alt at Ephemeris Time. For example, if you want to search for objects above 10°, you would enter 10 in Lowest Alt and leave 0 in Highest Alt. If both are 0, or if Ignore is checked, objects at all altitudes are included in the report. Leftmost Az and Rightmost Az operate in the same way. Note that Leftmost Az may be larger than Rightmost Az if you wish to specify an azimuth range that includes the pole.

Select Near Equatorial Position to enter values into the RA, Decl or Radius boxes. RA and Decl are entered in the format selected in Preferences, so some of the boxes may be disabled. Select North or South for the declination. Radius specifies an angular distance from the Equatorial Position within which included objects must lie. It is always entered in decimal degrees and the maximum value is 90°.

If your computer is connected to a telescope or DSC you can use Get Scope to retrieve the current equatorial position of the telescope and set the RA and Decl boxes with the retrieved position (referred to J2000.0). Get Scope is disabled if telescope control is not set up or connected

You can also use Look Up to find the position of an object and set the RA and Decl boxes with the retrieved position. Cataloged object positions are referred to J2000.0 while planets, asteroids, and comets are referred to the epoch and equinox of the ephemeris date. See the appendix for more information about object designations.

What about?

If you want to search for a position near either of the celestial poles, you should enter 89°59'.9 (North or South) because the trigonometry at 90° is literally undefined.

I slewed my telescope to an object, then used Get Scope to set the Near Equatorial Position parameters to the current position of the telescope. Why isn't the retrieved Near Equatorial Position the same as the cataloged object's position that I slewed to? Deep-Sky Planner precesses a cataloged object's position to the epoch of the report's ephemeris date before sending the Slew To command to the telescope. Get Scope retrieves the actual position of the telescope which should be slightly different from the cataloged value.

Only the B-series and C-series charts are cross referenced in the Herald-Bobroff AstroAtlas. You can search within either series.

Chart numbering changed radically from the first edition to the second of Uranometria 2000.0. Be sure to select the correct edition for your chart search.