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# Turning Effect objects on or off

To list all the effects in an optical train, we do use the `effects` attribute.

Alternatively, we can call `opt.optics_manager.all_effects()`

```{code-cell} ipython3
import scopesim as sim

opt = sim.load_example_optical_train()
opt.effects
```

Turning an effect on or off is as simple as using setting the `.include` attribute to `true` or `False`:

```{code-cell} ipython3
opt["slit_wheel"].include = True
opt["slit_wheel"].include = False
```