en:documentation:solar_system

# Solar System

From the menu: Setup → Solar system
You can make settings for the Solar system objects in four tabs:

- Solar System
- Planet
- Comet
- Asteroid

NEO's (Near Earth Objects) demand a special approach to have them displayed.

## Solar System

You specify to calculate geocentric or topocentric positions. Always keep it to topocentric unless you want to compare the data with a printed ephemeris.

Also you can choose if SkyChart should consider Pluto as a planet or not.

The last option is to show or not some 33 faint satellites of the outer planets. Most of this satellites are never visible with any telescope from Earth so it make sens to disable this option.

## Ephemeris

To give you the best possible precision, the program uses the JPL DExxx ephemeris to compute the planet positions and the nutation.
To limit the download size, the included DE405 file with this software is limited for usage from the years 2000 to 2050.

You can add more files to cover an extended time range or to use other ephemeris. Download the binary files from ftp://ssd.jpl.nasa.gov/pub/eph/planets/Linux or ftp://ssd.jpl.nasa.gov/pub/eph/planets/SunOS.
Copy the linx* or unx* files to the installation folder under data\jpleph\ without creating a subdirectory. You must restart the program after adding or removal of files.

The software tries to load DE430, DE431, DE423, DE421, DE422, DE405, DE406, DE403, DE200 in this order.
The “lnx*” files are used in preference of the “unx*” because they do not require byte swapping.

If no file is found for the date, it uses plan404 by Steve Moshier that allows for computation from -3000 to +3000 with a precision better than one arc second.

If DE431 is present the planet calculation can be done between -13000 and +17000.

If you select a date for which there is no mean to compute the planets position, the planet display is automatically disabled. You need to click the Show planet button again after you return to a valid date.

## Planet

Here you can enable or disable the display of the Sun, planets and satellites on the chart.

Four modes to draw planets are available. You will notice the difference in fields of vision smaller than 2°.

Check the corresponding box to show a real time image of the Sun from the satellites SDO or SOHO.
Select the image you want from the list. The default AIA 4500 correspond to the visual aspect but you can also try the other wavelengths.
The image will be refresh after the selected time or each time you select another wavelength. Effective update frequency depend on the satellite operation, see the satellite web page for more information. The image source and time is indicated next to the Sun on the map.
This feature require an Internet connection and correct setting of the proxy server if required.

You can update the position of Jupiter's Great Red Spot (GRS) in longitude: Click at the big button Get the recent GRS measurement from JUPOS project, this download a file with recent measurement and update the values.
You can also open the Jupos page, click on GRS Longitude in the menu. Then look at the red dot at the bottom of the graph to get the most recent position of the GRS center. For example it was about 160 in December 2010:

You can check the Show Earth shadow too. When you check this, the position of the Earth shadow will be displayed on the chart as two concentric circles, slightly darker than the background. The dimensions of the circles correspond to the size of the Earth shadow at the distance of the Moon, in order to simulate the lunar eclipses. The core shadow (umbra) is displayed in the middle, around it is the zone of partial eclipse (penumbra).
Transparent line mode allows the stars to be displayed behind planets or the Moon. This can be useful with occultations, to predict where the star will reappear.

## Comet

Before SkyCharts can display any comets, you must load a file with the orbital elements of the comets in the database on your computer. The usual way to achieve this, is simply to download the file of the latest version from the Minor Planet Center (MPC). You can also add new comet orbital elements, delete all entries, or selectively delete obsolete entries from the database. There are four tabs in this window:

- General Setting where you can choose to:
  - enable or disable the display of comets on the chart.
  - display the comet as a fixed symbol, or with a tail, sized proportional to its estimated magnitude.
  - filter comets below a limiting magnitude. You can display comets with a given magnitude fainter than the faintest displayed stars.

- Load MPC File
  - Download button to retrieve the last file with orbital elements for comets from IAU Minor Planet Center and store the information in the database. The source file will be saved as COMET-yyyy-mm-dd.DAT, where yyyy-mm-dd is the date of download.
    If downloading is a problem, check the upper part of the Setup → Internet → Orbital elements dialog box.
  - Or use a local file: with its directory icon gives you the opportunity to load any COMETxxx.DAT in the database with Load file button. It will be used automatically after you load it.
  - A message window will display the processing steps and the results.

- Data Maintenance where you can delete obsolete entries in the database, or delete the all the comet information from the database. A message window displays the processing steps and the results.

- Add where you can add orbital elements for a new comet in your database.

- Have a look here about how to enter the orbital element data.

## Asteroid

Before SkyChart can display asteroids, you need to have a file with the orbital elements of the asteroids. It is quite simple to download the data of the latest version from the Minor Planet Center (MPC) to use in the database on your computer. You can also add new asteroid orbital elements, delete all entries, or selectively remove obsolete entries from your database.

There are five tabs in this window:

- General Setting where you can choose to:
  - enable or disable the display of asteroids on the chart.
  - show asteroids as a symbols, or as stars, proportional to their magnitude.
  - filter asteroids below a limiting magnitude. You can display asteroids with a given magnitude fainter than the faintest displayed stars.

- Load MPC File
  - Download button to retrieve the last version file with the orbital elements of asteroids(bright, unusual and distant asteroids) from IAU Minor Planet Center and store the information in the database. The source files will be saved in a file like: MPCORB-yyyy-mm-dd.DAT where yyyy-mm-dd is the date of download.
    If downloading is a problem, check bottom part of the Setup → Internet → Orbital elements dialog box.
  - with Use a local file and its directory icon, you can specify any MPCORBxxx.DAT and load it in the database with the Load file button. It is automatically used after download.
  - A message window will display the processing steps and the results.

- Prepare Monthly Data process the orbital elements data to put it in the database for the given months range. A message window will display the processing steps and results.

- Data Maintenance where you can delete a single obsolete entry. Or if you wish, all asteroid information older than a given month from the database, or all the asteroid information from database. A message window will display the processing steps and the results.

- Add where you can add orbital elements for a new asteroid in your database.

- Have a look here about how to enter the orbital element data.

## Near Earth Objects

NEOs demand an entirely different approach to get their positions displayed with sufficient certainty. You will need to download calculated position data to build a catalogue using CatGen. For further details, please have a look here.