# Internet

## Proxy

From the menu: Setup → Internet → Proxy

- HTTP Proxy

If you are connected to Internet through a proxy, SkyCharts needs its parameters to work.
The parameters are:

- Proxy host IP address or hostname of the proxy.
- Port port number used to communicate with the proxy.
- User Name Name used to connect to proxy.
- Password password used to connect to proxy.

The default is not to use a proxy. If you don't need a proxy, then you don't need those parameters.

- FTP is used by SkyChart to download the larges files from MPC, an anonymous connection is required. If you are nice, you put your email address as a password here. Anyhow, it usually will work with anything that contains an ”@” in the password.

You can skip to push the download button every time you want to retrieve data from online resources. To do so, you need to uncheck the checkbox “Ask confirmation before any Internet connection” at the bottom of this tab.

## Orbital Elements

From the menu: Setup → Internet → Orbital Elements
Here the MPC URLs are specified that SkyChart can use to download the orbital elements of comets and asteroids.

### Comets

The upper input area contains the URLs for comets, you can choose the site and protocol to download from by a click on one of the four buttons:

- MPC Ftp comet data from cfa-ftp.harvard.edu by the FTP protocol
- MPC Http same as above, only HTTP protocol
- Default sets the URL to the same as MPC HTTP.

### Asteroids

The lower input area shows the MCP URLs that are used for asteroids, you can choose the source for the orbital elements by clicking one of the six buttons:

- MPCORB > 70MB! for full file (more than 300.000 asteroids, FTP protocol mandatory)
- First 5000 for a choice of 5000 asteroids (file downloaded from CdC Site)
- Bright + NEO + TNO For three MPC lists of asteroids (bright, unusual and distant)
- Default is same as First 5000 + NEO + TNO.
- astro.cz > 70B! A MPC-mirror situated in the Czech Republic. 300.000 asteroids, by HTTP
- First 5000 + NEO + TNO 5000 asteroids + the unusual and distant

## Online DSS pictures

From the menu: Setup → Internet → Online DSS
Here the DSS URLs are specified that you can use to download FITS formatted pictures. Each row in the list has a name and a URL. The name is used as a short identifier for the long URL. The URLs describe where and exactly how to download the pictures from. (see for example the DSS Site for details).

The names are used to select the source of your pictures, make your selection by a click on the icon in object tool bar, or by clicking Chart → Get DSS Image.

When you are an experienced user and you know pretty well what to do, you can add more rows with this dialog box. You will not break anything if the syntax is wrong, the worst that can happen is that the program will not be able to retrieve a picture by a faulty URL.
First you need to find out the syntax and the type of parameters that the website can handle. When you know this, you need to fill the variables for the parameters with the values that automatically will be delivered by Cartes du Ciel-Skychart.
Now, just click an empty line, enter a short name at the left. At the right, enter the complete URL with the proper variables from Cartes du Ciel-Skychart on the right places.
The next list gives you an overview of the variables that Cartes du Ciel-Skychart uses to generate the query URLs.

SkyChart variable | meaning
--- | ---
$RAH | Center coordinates, Right Ascension Hours
$RAM | Center coordinates, Right Ascension Minutes
$RAS | Center coordinates, Right Ascension Seconds
$DED | Center coordinates, Declination Degrees, North of celestial equator is prefixed with +, south prefixed by -
$DEM | Center coordinates, Declination Minutes
$DES | Center coordinates, Declination Seconds
$RAF | Center coordinates, Right Ascension, in decimal degrees of arc
$DEF | Center coordinates, Declination, decimal degrees. North of celestial equator is represented without a sign, south prefixed by -
$XSZ | FOV in X direction, decimal minutes of arc, precision 3 digits
$YSZ | FOV in Y direction, decimal minutes of arc, precision 3 digits
$FOVX | FOV in X direction, decimal degrees of arc, precision 6 digits
$FOVY | FOV in Y direction, decimal degrees of arc, precision 6 digits
$PIXX | Pixels in X direction
$PIXY | Pixels in Y direction

To read about the URL-format in queries, read the ASU document.
To read more about how to download a picture from DSS, click here.
To read more about the display of these images, click here.
To read more about the configuration of the usage of DSS, click here.