Introduction to LADIC

A small introduction to LADIC

Motivation

LADIC is the acronym for Luis Argüelles Difficulty Index C alculator, and is the name of a program that will help amateur astronomers to calculate his/her options to resolve a pair of double stars.

In July 2000, Luis Argüelles developed a method to calculate a value that classifies a double star by its difficulty to be split by amateur astronomers using amateur observing instruments. This is called the "Difficulty Index", or DI for short. His method is based on a branch of Artificial Intelligence called Fuzzy Logic. You can found more information about DI, its theoretical foundation and its development from Luis' web site.

In the last month, I have been working in a project that involves selecting a subgroup of double stars from the Washington Double Star Catalogue (WDS) that will be observable with modest telescopes. When I begun to apply filter criteria to the WDS data, quickly was evident that I need something like DI to make the selection.

After talking with Luis about this, he send me a couple of Control Surfaces (a portable discretization of a Fuzzy Intelligent Model) that enabled me to calculate DI after applying some interpolation techniques. This was the birth of LADIC...

Installing LADIC

The available distribution of LADIC is a ZIP file with four files inside:

DI-GRANDE.SFR: Control surface with a grid of 100x100
DI-MEDIA.SFR: Control surface with a grid of 50x50
LADIC.exe: The program
WDSSample.txt: Sample of WDS Catalogue.

To install LADIC you should unzip the file in a directory in your computer. That's all. After that, a double-click over LADIC.EXE will start the program and load by default the 100x100 Control Surface.

Using LADIC

This is the main and only window of LADIC. Here you can see three panels:

Top,Left: Control Surface selection and information
Bottom, Left: Discrete DI calculation
Right: Catalogue processing

Control Surface Selection

By default LADIC uses a grid of 100x100 values. If you have memory problems, you can try to load the lower resolution one.

Discrete DI Calculation

To calculate the DI for one double star, you should input the separation between components in arc seconds and the difference in magnitude in the appropriated text box. After that, pressing the Calculate button, you get the DI of the system. If your input values are outside the range of use of this model you get a value of -1.

Catalogue Processing

Computing DI star by star will be useful for a couple of pairs, but if you need to compute DI for a big set of stars, is better to put them on an ASCII file.

For example, suppose that you need to calculate DI for all the entries in the WDS Catalogue. The first thing you must do is to define the format of the data in the catalogue. Following the sample of WDS and taking a look to the sample file:

00000+7530 A  1248       1904 1982  5 246 235   0.8   0.6 10.5  11.5                      +74 1056    
00000+4004 ES 2543       1931 1931  1 252 252   4.8   4.8 11.0  12.0                                  
00000+3852 BU  860       1881 1933  8 107 110   6.7   6.8  6.6  11.4  B9        +003 -006 +38 5108  pD
00001+5400 ES  704       1908 1993  2 119 116   5.5   4.4  9.5  11.5

we can see that separation begins in column 53 and is 5 characters long, the magnitude for the primary component begins in column 59 and also have a length of 5 and finally the secondary component of each pair starts at column 64 for 5 chars. This is exactly the default values that LADIC shows in the start-up

Once you have selected the data file and described the format, you can press the Test button that will read the first 50 entries in the list, extract the data and compute the DI. LADIC will show this data on the list box at the bottom of this panel:

This preview is intended to help you in the process of correctly define the format. Once you have a good output from the Test button, you can press the Process button to get an output file called DI_InputFileName with the DI appended to each line. If one system don't fit in this model, the last column is empty.

Acknowledgements

LADIC is only a calculator that interpolates the data from the Control Surface. The real work of creating and computing the DI was done by Luis Argüelles and I want to express my congratulation to him for making this wonderful use of AI.

June 2001
Rafael Barberá