This button calls a dialogue box which lets you specify some options concerning star databases. These options are as follows:
For the Guide Star catalogue, you can choose whether or not to display non-stellar objects (they would be displayed in green). You can also specify if you want to display or not the multiple observations at different epochs on the same object (this applies only to the Guide Star 1.2 and Guide Star ACT catalogues).
For the USNO-SA1.0, USNO-A2.0 and USNO-B1.0 catalogues, you can choose whether you want to display the red or the blue magnitude on the screen. One can also specify to ignore stars without magnitude when a magnitude filter is positioned.
For the Tycho-2 catalogue, you can choose whether you want to display the visual or blue magnitude. You can also choose whether or not to take into account proper motions when calculating positions.
For the Hipparcos catalogue, you can choose whether to display the visual or the blue magnitude. You can also choose whether or not to take into account proper motions when calculating positions and if you want to use colours which reflect the stars’ spectral types.
For the UCAC1, UCAC2, UCAC3 and UCAC4 catalogues, you can choose whether or not to take into account proper motions when calculating positions. You can also select the photometric band to use for magnitudes in the UCAC3 and UCAC4 catalogues and also specify that you wish to use magnitudes band priorities or compound instrumental magnitudes. For more details, refer to the section Priority and Compound Magnitudes.
For the UCAC4 catalogue, you can choose whether or not to take into account proper motions when calculating positions. You can also select the photometric band to use for magnitudes. One can also specify to ignore stars without magnitude when a magnitude filter is positioned.
For the NOMAD catalogue, you can choose whether or not to take into account proper motions when calculating positions. You can request not to display stars which have an uncertain status and select the photometric band to use for magnitudes. You can also request not to display stars which have an uncertain status and select the photometric band to use for magnitudes. Finally, you can also specify that you wish to use magnitudes band priorities or compound instrumental magnitudes. For more details, refer to the section Priority and Compound Magnitudes.
For the PPMXL catalogue, you can choose whether or not to take into account proper motions when calculating positions. You can also select the photometric band to use for magnitudes. You can also request not to display stars which have an uncertain status and select the photometric band to use for magnitudes. There is also the possibility to re-generate the catalogue index (used to accelerate the access to the catalogue), but it is usually not necessary to perform this action since the index is delivered by default with C2A. This possibility exists however if a new version of the catalogue is published in the future. Note that this process can take up to several hours to complete. Finally, you can also specify to ignore stars without magnitude when a magnitude filter is positioned and specify that you wish to use magnitudes band priorities or compound instrumental magnitudes. For more details, refer to the section Priority and Compound Magnitudes. There is normally no need to recompile the PPMXL catalogue index since it is provided with the C2A distribution.
For the CMC15 catalogue, you can specify to ignore stars without magnitude when a magnitude filter is positioned. You can also select the magnitude band to be used in the field displays. There is normally no need to recompile the CMC15 catalogue index since it is provided with the C2A distribution.
For the URAT1 catalogue, you can choose whether or not to take into account proper motions when calculating positions, you can specify to ignore stars without magnitude when a magnitude filter is positioned and you can also select the magnitude band to be used in the field displays.
For the WDS catalogue, you can request the usage of multiple-star symbols in the maps and specify is colored stars have to be used and you can choose whether or not to take into account proper motions when calculating positions.
For the asterism catalogue, you can specify a size limit in arc minutes above which asterisms will not be displayed in the maps. If you don’t want to set a limit, just leave the input box empty.