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## Name

ccdl2 - find the Lagrangian points in a 2D potential

## Synopsis

ccdl2 [parameter=value]

## Description

For a 2D potential (or any image) on a grid, this program will list the local minima, maxima and saddle points. In rotating potentials these are the L1, L2, L3, L4 and L5 lagrangian points.

For a barred galaxy (see e.g. Sellwood & Wilkinson, 1993) L3 (center), L4 and L5 (along minor axis) are stable, whereas L1,L2 (along major axis) are unstable.

For a two-body system L4,L5 are stable (as long as the mass ratio > 24.96), and L1,L2,L3 are all unstable!

## Parameters

The following parameters are recognized in order; they may be given in any order if the keyword is also given. Use --help to confirm this man page is up to date.
in=
Input image file [???]

## Examples

Here is

```    % potccd  2body_0.2 potname=twobody potpars=-1,0.2,1,0.05 x=-2:2:0.01 y=-2:2:0.01
% ccdl2   2body_0.2
### Warning [ccdl2]: Draft program
### nemo Debug Info: Dx,Dy= 0.01 0.01
###: IX0 IY0   X     Y    Potential
L00: 240 112   0.4  -0.88  -1.59263
L00: 241 113   0.41 -0.87  -1.59264
L01:  85 200  -1.15  0     -1.80542
L11: 180 200  -0.2   0    -20.1865
L01: 257 200   0.57  0     -1.92043
L11: 300 200   1     0     -5.33261
L01: 343 200   1.43  0     -2.09766
L00: 241 287   0.41  0.87  -1.59264
L00: 240 288   0.4   0.88  -1.59263
% ccdplot 2body_0.2 contour=-3.5,-2.09766,-1.92043,-1.80542,-1.7,-1.6
```

Where L00 is a local maximum, L11 a local minimum, and L01/L10 are saddle points. The contour plot can thus use the potential values of the critical saddle points L1, L2 and L3.

potccd(1NEMO) , potlist(1NEMO) , potential(5NEMO) , image(5NEMO)

## Files

NEMO/src/image/misc

Peter Teuben

## Update History

```1980s       CYBER version for my thesis    PJT
9-jan-22    V0.1 drafted from scratch    PJT
```