C2A for Windows has a simple and user friendly interface. It is possible at any time to know the cursor position within the field through a dialog zone at the bottom of the screen. The picture below provides a global view of the user interface (simply click it to enlarge the view):

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C2A is able to display stars under the form of colored disks as well as "synthetic" stars that reproduce star aspect similar to what is obtained in CCD image:

A simple and powerful Search box makes the process to locate any object from the different databases easy. One can see on this picture that it is possible to perform a search on:

a Solar System object;
a star through its name, SAO number or Tycho-2 or Hipparcos reference;
a constellation or a star in a constellation through its Bayer or Flamsteed designation;
an object in the BT-Atlas catalogue (when this catalogue is activated otherwise this zone is not active);
a Deep Sky object through its NGC, IC or Messier reference.

A quick search zone is available in order to quickly enter an object name (e.g. moon, M42, NGC5423, ...). For this particular zone, the search is launched just by typing the Enter key.

Many options are available to customize field views. All these options are gathered in a single dialog box with several tabs (in order to provide the user with a simple and consistent way to customize views). One can see in the picture below all the options organized in 10 different tabs:

Some options from this dialog box are directly accessible from the menu or through keyboard shortcuts. The figure below shows an example of such a menu:

One of the two Deep Sky object catalogue provided with C2A includes: the Messier catalogue, the NGC catalogue and the IC catalogue. This catalogue is built from the original «Revised New General Catalog» well know by the astronomers community. It is enhanced with the NGC 2000 catalogue in order to get some object sizes.

C2A is able to read the BT-Atlas catalogue and to display all the associated images. It is a unique set of 4649 images representing 6600 deep sky objects. All these images were acquired using CCD cameras. There are 5002 galaxies, 284 galaxy clusters, 654 open clusters, 136 globular clusters, 155 planetary nebulae, 279 diffuse nebulae and et 90 dark nebulae.

C2a is able to display the Milky Way at any zoom level. A computation using Bezier's curves guarantees round shapes.

Furthermore, when the RNGCIC catalogue ("Revised New General Catalogue and Index Catalogue") is displayed, a certain number of diffuse nebulae are displayed using their approximate shapes on the sky background. Some shapes are associated specifically to NGC and IC obecjts (in which case they are displayed with the light green color) and some others are not (in which case they are displayed with the dark green color).

Regarding Solar System, positions computing of the Sun, Moon and planets are performed using some special algorithms from the Institut de Mécanique Céleste (Bureau des Longitudes) in Paris. Polynomial coefficients used in these algorithms provide a very high accuracy on object positions (1/100 arc second over the period 1987/2020). The figure below shows Mars path with a retrogradation:

C2A integrates a tool to view planet, asteroid and comet positions according to an ecliptic view (accessible from the Tools menu). It is possible to easily change the angle of view as well as the zoom level. Furthermore, an animation mode is available.

C2A includes a full Ephemeris production system (Moon, Sun, planets as well as comets and asteroids know through their orbital elements). The output step can be adjusted and the produced ephemeris can be saved under the form of a text file or directly printed. The picture below show an example of such an ephemeris (click the picture to enlarge it):

C2A now includes a module to compute and display Moon phases for a given month. Furthermore, dates of Full Moon, New Moon, First Quarter and Second Quarter are specifically provided.

C2A includes a powerful system to compute asteroid and comet position calculation from their orbital elements. A Graphical User Interface allows the user to import and handle orbital elements. The figure below shows this graphical interface:

It is possible to import orbital elements directly from the Internet (using for instance the Minor Planet Center Web site). Several orbital elements formats are supported. The picture below shows the import interface:

Once the orbital elements are loaded, it is then possible to plot positions or paths of the objects. The picture below shows an example of an asteroid path:

C2A has the capability to access the images of the Digitized Sky Survey (DSS) from the ESO and STScI and to display these images in a separate window or in the background of the current field. In this version, the access to the DSS is only performed through Internet on the ESO DSS server (http://archive.eso.org/dss/dss) or STScI server (http://archive.stsci.edu/cgi-bin/dss_form). In order to access these images, your platform must be connected to the Internet.

The following surveys can be accessed on the ESO server:

The figure below displays a field view with an ESO DSS image in the background and the Tycho-2 and RNGCIC catalogue objects in the foreground (note the slight rotation of the image, which is performed automatically, in order to get a perfect mapping with the objects from the catalogues).

The figure below shows an other example of a field with two galaxies:

User has the possibility to add its own images in the C2A environment. Once one or several images are associated to a given object (for instance a Messier or an NGC object), access to those images images is performed thtough the button Image... in the information window displayed for that object. The command Image... in the contextual menu can also be used.

Object types to which images can be associated to are the following: deep sky objects from standard deek sky and RNGCIC catalogues, SAO stars, user objects, Tycho2 star, UCAC1 and UCAC2 stars, planet, Moon, Sun and satellite.

User can also associate a text of his/her choice to a given image (for example some comments about howw the image was acquired). This text is then automatically displayed in an information box associated to the image.

All the images must be stored in a directory declared in the Path tab of the Options dialog box. The first image associated to an object must be named according to the pattern <object name>_1.<extention> where <object name> is the name of the object displayed in the information window and <extension> is the file extension associated to one of the supported image formats (fit, fts, fits, pic, jpg, gif and bmp ). For example, the first JPEG image associated to the object NGC 1972 must be named NGC 1972_1.jpg. The second one must be named NGC 1972_2.jpg, etc...

C2A gives the possibility to display planetary positions at 3 different dates for a given month. This display is performed either at the beginning, middle or end of the night. It is done on a map with constant azimut and altitude. This is a useful tool to see at a glance what are going to be the observing conditions for a given object during a given month.

It is possible to parameterize the display through numerous options.

C2A for Windows offers the possibility to control a telescope through a serial port. By controlling, we mean the following features:

• Display the telescope position in Right Ascension and Declination.
• Display current telescope position under the form of a target in a map.
• Possibility to calibrate the telescope controller from C2A (i.e. indicate the telescope controller which point in the sky it is currently pointing at).
• Possibility to move the telescope (slew) to a specific target (whose Right Ascension and Declination are provided by the user).

Supported telescopes are the following:

• All the Telescopes and focusers compatible with the ASCOM standard (see http://ascom-standards.org/)
• Telescope Meade LX200 (or any other telescope that supports the standard native LX200 protocole). C2A has been validated on an LX200 / 2 - version 3.30L and version 4.341L (AltAz mode).
• Telescope controller SkySensor 2000 PC. C2A has been validated on a SkySensor 2000 PC version 2.10.
• AudeCom controller.

C2A includes a tool to analyze and plot tracking drifts for telescope mountings. In its current version, C2A is able to read data files produced by the Iris software (see http://www.astrosurf.org/buil/iris/iris.htm).

The sceen snapshot below shows data produced by the Iris software and graphically represented:

C2A offers the user the possibility to "zoom" on some parts of the plot and to copy an image of the plot for future usage. To use this tool, go into the menu "Telescope" and use the command "Tracking Drift Analysis...".

Maps and Ephemeris can be printed on all the printers supported by the Windows Operating System. Several options are possible to improve printing results. The picture below shows the printing options in the dialog box:

To see a printing result in the PDF format, click here.

C2A is able to take into account proper motions for the stars in the catalogues UCAC1, UCAC2, Hipparcos and Tycho-2. Click on the picture below to see the successive positions of the Barnard's star between 1959 and 2030. This animated image has been created with the UCAC2 catalogue.

C2A for Windows includes a tool to help focusing a telescope. This tool is accessible from the Image Processing window once a star has been selected with the mouse. User then simply has to click the Focus button in the tool bar.

This tool allows the user to easily see how focus evolves while focus images arrive in a pre-defined directory during the focus process. Focus is plot dynamically through an automatic analysis of the in-coming images.