# Air mass coefficient (dialog)

The “Air mass coefficient” allows an user to compute air mass coefficient for specified star, location and date of observation. The object’s altitude in degrees is also presented.

## Activating the dialog

The dialog can be activated:

1. from the main menu: Tools ‣ Air mass coefficient.

## Computing air mass coefficient and object’s altitude

Computing air mass coefficient and object’s altitude

Enter object’s right ascension to the text box (1) in hours. Use the hexagesimal format, separate the fields by a space character.

Enter object’s declination to the text box (2) in degrees. Use the hexagesimal format, separate the fields by a space character.

Click the ellipsis button (3) to retrieve object’s coordinates from a table of predefined objects or a catalog of variable stars.

Enter observer’s longitude to the text box (4) in degrees. Use the hexagesimal format, separate the fields by a space character. Enter ‘E’ character at the first position in a string to indicate that the location is on the eastern hemisphere or ‘W’ character for locations on a western hemisphere.

Enter observer’s latitude to the text box (5) in degrees. Use the hexagesimal format, separate the fields by a space character. Enter ‘N’ character at the first position in s string to indicate that the location is on the north hemisphere or ‘S’ character for locations on a southern hemisphere.

Click the ellipsis button (6) to retrieve observer’s coordinates from a table of predefined locations.

Enter a Julian date into the text box (7) or date and time into the text box (8). As you type in the data, corresponding value of air mass coefficient and altitude is updated in the last two text boxes (9, 10).

See also

JD converter (dialog), Heliocentric correction (dialog)