diff --git a/ctapipe/conftest.py b/ctapipe/conftest.py
index cec3dcce2a2..891d4658c90 100644
--- a/ctapipe/conftest.py
+++ b/ctapipe/conftest.py
@@ -44,7 +44,8 @@ def _global_example_event():
 
     print("******************** LOAD TEST EVENT ***********************")
 
-    with SimTelEventSource(input_url=filename) as reader:
+    # FIXME: switch to prod5b+ file that contains effective focal length
+    with SimTelEventSource(input_url=filename, focal_length_choice='nominal') as reader:
         event = next(iter(reader))
 
     return event
@@ -59,7 +60,7 @@ def example_subarray():
 
     print("******************** LOAD TEST EVENT ***********************")
 
-    with SimTelEventSource(input_url=filename) as reader:
+    with SimTelEventSource(input_url=filename, focal_length_choice='nominal') as reader:
         return reader.subarray
 
 
@@ -84,7 +85,7 @@ def _subarray_and_event_gamma_off_axis_500_gev():
 
     path = get_dataset_path("lst_prod3_calibration_and_mcphotons.simtel.zst")
 
-    with SimTelEventSource(path) as source:
+    with SimTelEventSource(path, focal_length_choice='nominal') as source:
         it = iter(source)
         # we want the second event, first event is a corner clipper
         next(it)
@@ -353,6 +354,7 @@ def dl1_muon_file(dl1_tmp_path):
             "--write-images",
             "--DataWriter.write_parameters=False",
             "--DataWriter.Contact.name=αℓℓ the äüöß",
+            "--SimTelEventSource.focal_length_choice=nominal",
         ]
         assert run_tool(ProcessorTool(), argv=argv, cwd=dl1_tmp_path) == 0
         return output
diff --git a/ctapipe/io/eventseeker.py b/ctapipe/io/eventseeker.py
index 3c58643db8a..bb77b069c12 100644
--- a/ctapipe/io/eventseeker.py
+++ b/ctapipe/io/eventseeker.py
@@ -28,7 +28,7 @@ class EventSeeker(Component):
     To obtain a particular event in a simtel file:
 
     >>> from ctapipe.io import SimTelEventSource
-    >>> event_source = SimTelEventSource(input_url="dataset://gamma_test_large.simtel.gz")
+    >>> event_source = SimTelEventSource(input_url="dataset://gamma_test_large.simtel.gz", focal_length_choice="nominal")
     >>> seeker = EventSeeker(event_source=event_source)
     >>> event = seeker.get_event_index(2)
     >>> print(event.count)
@@ -37,7 +37,7 @@ class EventSeeker(Component):
     To obtain a particular event in a simtel file from its event_id:
 
     >>> from ctapipe.io import SimTelEventSource
-    >>> event_source = SimTelEventSource(input_url="dataset://gamma_test_large.simtel.gz", back_seekable=True)
+    >>> event_source = SimTelEventSource(input_url="dataset://gamma_test_large.simtel.gz", back_seekable=True, focal_length_choice="nominal")
     >>> seeker = EventSeeker(event_source=event_source)
     >>> event = seeker.get_event_id(31007)
     >>> print(event.count)
diff --git a/ctapipe/io/eventsource.py b/ctapipe/io/eventsource.py
index 4b46f33c4b5..61a9c50c058 100644
--- a/ctapipe/io/eventsource.py
+++ b/ctapipe/io/eventsource.py
@@ -36,7 +36,7 @@ class EventSource(Component):
     appropriate subclass if a compatible source is found for the given
     ``input_url``.
 
-    >>> EventSource(input_url="dataset://gamma_test_large.simtel.gz")
+    >>> EventSource(input_url="dataset://gamma_prod5.simtel.zst")
     <ctapipe.io.simteleventsource.SimTelEventSource ...>
 
     An ``EventSource`` can also be created through the configuration system,
@@ -45,7 +45,7 @@ class EventSource(Component):
     >>> self.source = EventSource(parent=self) # doctest: +SKIP
 
     To loop through the events in a file:
-    >>> source = EventSource(input_url="dataset://gamma_test_large.simtel.gz", max_events=2)
+    >>> source = EventSource(input_url="dataset://gamma_prod5.simtel.zst", max_events=2)
     >>> for event in source:
     ...     print(event.count)
     0
@@ -58,7 +58,7 @@ class EventSource(Component):
     It is encouraged to use ``EventSource`` in a context manager to ensure
     the correct cleanups are performed when you are finished with the source:
 
-    >>> with EventSource(input_url="dataset://gamma_test_large.simtel.gz", max_events=2) as source:
+    >>> with EventSource(input_url="dataset://gamma_prod5.simtel.zst", max_events=2) as source:
     ...    for event in source:
     ...        print(event.count)
     0
diff --git a/ctapipe/io/simteleventsource.py b/ctapipe/io/simteleventsource.py
index 853a47910b5..cdab4f590cb 100644
--- a/ctapipe/io/simteleventsource.py
+++ b/ctapipe/io/simteleventsource.py
@@ -180,7 +180,7 @@ class SimTelEventSource(EventSource):
 
     focal_length_choice = CaselessStrEnum(
         ["nominal", "effective"],
-        default_value="nominal",
+        default_value="effective",
         help=(
             "if both nominal and effective focal lengths are available in the "
             "SimTelArray file, which one to use when constructing the "
@@ -306,26 +306,31 @@ def prepare_subarray_info(self, telescope_descriptions, header):
             pixel_settings = telescope_description["pixel_settings"]
 
             n_pixels = cam_settings["n_pixels"]
-            focal_length = u.Quantity(cam_settings["focal_length"], u.m)
             mirror_area = u.Quantity(cam_settings["mirror_area"], u.m**2)
 
-            if self.focal_length_choice == "effective":
-                try:
-                    focal_length = u.Quantity(
-                        cam_settings["effective_focal_length"], u.m
-                    )
-                except KeyError as err:
-                    raise RuntimeError(
-                        f"the SimTelEventSource option 'focal_length_choice' was set to "
-                        f"{self.focal_length_choice}, but the effective focal length "
-                        f"was not present in the file. ({err})"
-                    )
+            nominal_focal_length = u.Quantity(cam_settings["focal_length"], u.m)
+            effective_focal_length = u.Quantity(
+                cam_settings.get("effective_focal_length", np.nan), u.m
+            )
 
             try:
-                telescope = guess_telescope(n_pixels, focal_length)
+                telescope = guess_telescope(n_pixels, nominal_focal_length)
             except ValueError:
                 telescope = unknown_telescope(mirror_area, n_pixels)
 
+            if self.focal_length_choice == "effective":
+                if np.isnan(effective_focal_length):
+                    raise RuntimeError(
+                        f"`SimTelEventSource.focal_length_choice` was set to"
+                        f" {self.focal_length_choice!r}, but the effective focal length"
+                        f" was not present in the file. "
+                        " Use nominal focal length or adapt your simulation configuration"
+                        " to include the effective focal length"
+                    )
+                focal_length = effective_focal_length
+            else:
+                focal_length = nominal_focal_length
+
             optics = OpticsDescription(
                 name=telescope.name,
                 num_mirrors=telescope.n_mirrors,
diff --git a/ctapipe/io/tests/conftest.py b/ctapipe/io/tests/conftest.py
index 27705d2c05a..8c818a23302 100644
--- a/ctapipe/io/tests/conftest.py
+++ b/ctapipe/io/tests/conftest.py
@@ -1,6 +1,5 @@
 import pytest
 from ctapipe.io import EventSource, DataWriter
-from ctapipe.utils import get_dataset_path
 
 
 @pytest.fixture(scope="session")
@@ -9,11 +8,10 @@ def r1_path(tmp_path_factory):
 
 
 @pytest.fixture(scope="session")
-def r1_hdf5_file(r1_path):
+def r1_hdf5_file(prod5_proton_simtel_path, r1_path):
     source = EventSource(
-        get_dataset_path("gamma_LaPalma_baseline_20Zd_180Az_prod3b_test.simtel.gz"),
+        prod5_proton_simtel_path,
         max_events=5,
-        allowed_tels=[1, 2, 3, 4],
     )
 
     path = r1_path / "test_r1.h5"
diff --git a/ctapipe/io/tests/test_datawriter.py b/ctapipe/io/tests/test_datawriter.py
index 97feb96d752..ce5d0f24cb9 100644
--- a/ctapipe/io/tests/test_datawriter.py
+++ b/ctapipe/io/tests/test_datawriter.py
@@ -51,6 +51,7 @@ def test_write(tmpdir: Path):
         get_dataset_path("gamma_LaPalma_baseline_20Zd_180Az_prod3b_test.simtel.gz"),
         max_events=20,
         allowed_tels=[1, 2, 3, 4],
+        focal_length_choice='nominal',
     )
     calibrate = CameraCalibrator(subarray=source.subarray)
 
@@ -131,6 +132,7 @@ def test_roundtrip(tmpdir: Path):
         get_dataset_path("gamma_LaPalma_baseline_20Zd_180Az_prod3b_test.simtel.gz"),
         max_events=20,
         allowed_tels=[1, 2, 3, 4],
+        focal_length_choice='nominal',
     )
     calibrate = CameraCalibrator(subarray=source.subarray)
 
@@ -203,7 +205,7 @@ def test_dl1writer_no_events(tmpdir: Path):
 
     output_path = Path(tmpdir / "no_events.dl1.h5")
     dataset = "lst_prod3_calibration_and_mcphotons.simtel.zst"
-    with EventSource(get_dataset_path(dataset)) as source:
+    with EventSource(get_dataset_path(dataset), focal_length_choice='nominal') as source:
         # exhaust source
         for _ in source:
             pass
@@ -233,7 +235,7 @@ def test_dl1writer_no_events(tmpdir: Path):
 def test_metadata(tmpdir: Path):
     output_path = Path(tmpdir / "metadata.dl1.h5")
 
-    dataset = "lst_prod3_calibration_and_mcphotons.simtel.zst"
+    dataset = "gamma_20deg_0deg_run2___cta-prod5-paranal_desert-2147m-Paranal-dark_cone10-100evts.simtel.zst"
 
     config = Config(
         {
diff --git a/ctapipe/io/tests/test_event_source.py b/ctapipe/io/tests/test_event_source.py
index a46f85061cf..9a839ff89dc 100644
--- a/ctapipe/io/tests/test_event_source.py
+++ b/ctapipe/io/tests/test_event_source.py
@@ -6,6 +6,8 @@
 
 from ctapipe.core import Component
 
+prod5_path = "gamma_20deg_0deg_run2___cta-prod5-paranal_desert-2147m-Paranal-dark_cone10-100evts.simtel.zst"
+
 
 def test_construct():
     # at least one of input_url / parent / config is required
@@ -43,20 +45,20 @@ def datalevels(self):
 
 
 def test_can_be_implemented():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     test_reader = DummyReader(input_url=dataset)
     assert test_reader is not None
 
 
 def test_is_iterable():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     test_reader = DummyReader(input_url=dataset)
     for _ in test_reader:
         pass
 
 
 def test_function():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     reader = EventSource(input_url=dataset)
     assert isinstance(reader, SimTelEventSource)
     assert reader.input_url == dataset
@@ -75,7 +77,7 @@ def test_function_nonexistant_file():
 
 
 def test_from_config():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     config = Config({"EventSource": {"input_url": dataset}})
     reader = EventSource(config=config)
     assert isinstance(reader, SimTelEventSource)
@@ -83,7 +85,7 @@ def test_from_config():
 
 
 def test_from_config_parent():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
 
     class Parent(Component):
         def __init__(self, config=None, parent=None):
@@ -109,7 +111,7 @@ def __init__(self, config=None, parent=None):
 
 def test_from_config_default():
     old_default = EventSource.input_url.default_value
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     EventSource.input_url.default_value = dataset
     config = Config()
     reader = EventSource(config=config, parent=None)
@@ -119,7 +121,7 @@ def test_from_config_default():
 
 
 def test_from_config_invalid_type():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     EventSource.input_url.default_value = dataset
     config = Config({"EventSource": {"input_url": 124}})
     with pytest.raises(TraitError):
@@ -127,10 +129,10 @@ def test_from_config_invalid_type():
 
 
 def test_event_source_input_url_config_override():
-    dataset1 = get_dataset_path("gamma_test_large.simtel.gz")
-    dataset2 = get_dataset_path(
+    dataset1 = get_dataset_path(
         "gamma_LaPalma_baseline_20Zd_180Az_prod3b_test.simtel.gz"
     )
+    dataset2 = get_dataset_path(prod5_path)
 
     config = Config({"EventSource": {"input_url": dataset1}})
     reader = EventSource(input_url=dataset2, config=config)
@@ -141,13 +143,13 @@ def test_event_source_input_url_config_override():
 
 def test_max_events():
     max_events = 10
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     reader = EventSource(input_url=dataset, max_events=max_events)
     assert reader.max_events == max_events
 
 
 def test_max_events_from_config():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     max_events = 10
     config = Config({"EventSource": {"input_url": dataset, "max_events": max_events}})
     reader = EventSource(config=config)
@@ -155,15 +157,15 @@ def test_max_events_from_config():
 
 
 def test_allowed_tels():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     reader = EventSource(input_url=dataset)
     assert reader.allowed_tels is None
     reader = EventSource(input_url=dataset, allowed_tels={1, 3})
-    assert len(reader.allowed_tels) == 2
+    assert reader.allowed_tels == {1, 3}
 
 
 def test_allowed_tels_from_config():
-    dataset = get_dataset_path("gamma_test_large.simtel.gz")
+    dataset = get_dataset_path(prod5_path)
     config = Config({"EventSource": {"input_url": dataset, "allowed_tels": {1, 3}}})
     reader = EventSource(config=config, parent=None)
-    assert len(reader.allowed_tels) == 2
+    assert reader.allowed_tels == {1, 3}
diff --git a/ctapipe/io/tests/test_eventseeker.py b/ctapipe/io/tests/test_eventseeker.py
index fee3119c380..58ec2547afa 100644
--- a/ctapipe/io/tests/test_eventseeker.py
+++ b/ctapipe/io/tests/test_eventseeker.py
@@ -8,7 +8,11 @@
 
 def test_eventseeker():
 
-    with SimTelEventSource(input_url=dataset, back_seekable=True) as reader:
+    with SimTelEventSource(
+        input_url=dataset,
+        back_seekable=True,
+        focal_length_choice='nominal',
+    ) as reader:
 
         seeker = EventSeeker(event_source=reader)
 
@@ -33,7 +37,8 @@ def test_eventseeker():
             seeker.get_event_index(dict())
 
     with SimTelEventSource(
-        input_url=dataset, max_events=5, back_seekable=True
+        input_url=dataset, max_events=5, back_seekable=True,
+        focal_length_choice='nominal',
     ) as reader:
         seeker = EventSeeker(event_source=reader)
         with pytest.raises(IndexError):
@@ -42,7 +47,10 @@ def test_eventseeker():
 
 
 def test_eventseeker_edit():
-    with SimTelEventSource(input_url=dataset, back_seekable=True) as reader:
+    with SimTelEventSource(
+        input_url=dataset, back_seekable=True,
+        focal_length_choice='nominal',
+    ) as reader:
         seeker = EventSeeker(event_source=reader)
         event = seeker.get_event_index(1)
         assert event.count == 1
@@ -54,7 +62,10 @@ def test_eventseeker_edit():
 
 def test_eventseeker_simtel():
     # Ensure the EventSeeker can forward seek even if back-seeking is not possible
-    with SimTelEventSource(input_url=dataset, back_seekable=False) as reader:
+    with SimTelEventSource(
+        input_url=dataset, back_seekable=False,
+        focal_length_choice='nominal',
+    ) as reader:
         seeker = EventSeeker(event_source=reader)
         event = seeker.get_event_index(1)
         assert event.count == 1
diff --git a/ctapipe/io/tests/test_hdf5eventsource.py b/ctapipe/io/tests/test_hdf5eventsource.py
index a8634e79985..eaab48b2b0f 100644
--- a/ctapipe/io/tests/test_hdf5eventsource.py
+++ b/ctapipe/io/tests/test_hdf5eventsource.py
@@ -136,4 +136,4 @@ def test_read_r1(r1_hdf5_file):
             pass
 
         assert e is not None
-        assert e.count == 4
+        assert e.count == 3
diff --git a/ctapipe/io/tests/test_prod2.py b/ctapipe/io/tests/test_prod2.py
index 200d2406014..98be8be0eb5 100644
--- a/ctapipe/io/tests/test_prod2.py
+++ b/ctapipe/io/tests/test_prod2.py
@@ -9,7 +9,10 @@
 
 def test_eventio_prod2():
     with pytest.warns(UnknownPixelShapeWarning):
-        with SimTelEventSource(input_url=dataset) as reader:
+        with SimTelEventSource(
+            input_url=dataset,
+            focal_length_choice='nominal',
+        ) as reader:
             for event in reader:
                 if event.count == 2:
                     break
diff --git a/ctapipe/io/tests/test_simteleventsource.py b/ctapipe/io/tests/test_simteleventsource.py
index d94a09c61b4..77eba9e8d12 100644
--- a/ctapipe/io/tests/test_simteleventsource.py
+++ b/ctapipe/io/tests/test_simteleventsource.py
@@ -2,8 +2,8 @@
 from ctapipe.instrument.camera.geometry import UnknownPixelShapeWarning
 
 import numpy as np
-from astropy.utils.data import download_file
 import astropy.units as u
+from astropy.coordinates import Angle
 from itertools import zip_longest
 import pytest
 from astropy.time import Time
@@ -20,18 +20,21 @@
 gamma_test_large_path = get_dataset_path("gamma_test_large.simtel.gz")
 gamma_test_path = get_dataset_path("gamma_test.simtel.gz")
 calib_events_path = get_dataset_path("lst_prod3_calibration_and_mcphotons.simtel.zst")
+prod5b_path = get_dataset_path("gamma_20deg_0deg_run2___cta-prod5-paranal_desert-2147m-Paranal-dark_cone10-100evts.simtel.zst")
 
 
 def test_positional_input():
-    source = SimTelEventSource(gamma_test_large_path)
-    assert source.input_url == Path(gamma_test_large_path)
+    source = SimTelEventSource(prod5b_path)
+    assert source.input_url == Path(prod5b_path)
 
 
 def test_simtel_event_source_on_gamma_test_one_event():
+    assert SimTelEventSource.is_compatible(gamma_test_large_path)
+
     with SimTelEventSource(
-        input_url=gamma_test_large_path, back_seekable=True
+        input_url=gamma_test_large_path, back_seekable=True,
+        focal_length_choice='nominal',
     ) as reader:
-        assert reader.is_compatible(gamma_test_large_path)
         assert not reader.is_stream
 
         for event in reader:
@@ -47,7 +50,7 @@ def test_simtel_event_source_on_gamma_test_one_event():
 
 def test_that_event_is_not_modified_after_loop():
 
-    dataset = gamma_test_large_path
+    dataset = prod5b_path
     with SimTelEventSource(input_url=dataset, max_events=2) as source:
         for event in source:
             last_event = copy.deepcopy(event)
@@ -61,12 +64,11 @@ def test_that_event_is_not_modified_after_loop():
 
 
 def test_additional_meta_data_from_simulation_config():
-    with SimTelEventSource(input_url=gamma_test_large_path) as reader:
-        next(iter(reader))
-
-    # for expectation values
-    from astropy import units as u
-    from astropy.coordinates import Angle
+    with SimTelEventSource(
+        input_url=gamma_test_large_path,
+        focal_length_choice='nominal',
+    ) as reader:
+        pass
 
     # There should be only one observation
     assert len(reader.obs_ids) == 1
@@ -104,7 +106,10 @@ def test_additional_meta_data_from_simulation_config():
 
 
 def test_properties():
-    source = SimTelEventSource(input_url=gamma_test_large_path)
+    source = SimTelEventSource(
+        input_url=gamma_test_large_path,
+        focal_length_choice='nominal',
+    )
 
     assert source.is_simulation
     assert source.datalevels == (DataLevel.R0, DataLevel.R1)
@@ -112,11 +117,14 @@ def test_properties():
     assert source.simulation_config[7514].corsika_version == 6990
 
 
-def test_gamma_file():
+def test_gamma_file_prod2():
     dataset = gamma_test_path
 
     with pytest.warns(UnknownPixelShapeWarning):
-        with SimTelEventSource(input_url=dataset) as reader:
+        with SimTelEventSource(
+            input_url=dataset,
+            focal_length_choice='nominal',
+        ) as reader:
             assert reader.is_compatible(dataset)
             assert reader.is_stream  # using gzip subprocess makes it a stream
 
@@ -134,7 +142,9 @@ def test_gamma_file():
 def test_max_events():
     max_events = 5
     with SimTelEventSource(
-        input_url=gamma_test_large_path, max_events=max_events
+        input_url=gamma_test_large_path,
+        max_events=max_events,
+        focal_length_choice='nominal',
     ) as reader:
         count = 0
         for _ in reader:
@@ -143,7 +153,11 @@ def test_max_events():
 
 
 def test_pointing():
-    with SimTelEventSource(input_url=gamma_test_large_path, max_events=3) as reader:
+    with SimTelEventSource(
+        input_url=gamma_test_large_path,
+        max_events=3,
+        focal_length_choice='nominal',
+    ) as reader:
         for e in reader:
             assert np.isclose(e.pointing.array_altitude.to_value(u.deg), 70)
             assert np.isclose(e.pointing.array_azimuth.to_value(u.deg), 0)
@@ -160,7 +174,8 @@ def test_allowed_telescopes():
     # test that the allowed_tels mask works:
     allowed_tels = {3, 4}
     with SimTelEventSource(
-        input_url=gamma_test_large_path, allowed_tels=allowed_tels, max_events=5
+        input_url=gamma_test_large_path, allowed_tels=allowed_tels, max_events=5,
+        focal_length_choice='nominal',
     ) as reader:
         assert not allowed_tels.symmetric_difference(reader.subarray.tel_ids)
         for event in reader:
@@ -188,7 +203,8 @@ def test_calibration_events():
         EventType.SUBARRAY,
     ]
     with SimTelEventSource(
-        input_url=calib_events_path, skip_calibration_events=False
+        input_url=calib_events_path, skip_calibration_events=False,
+        focal_length_choice='nominal',
     ) as reader:
 
         for event, expected_type in zip_longest(reader, expected_types):
@@ -197,7 +213,10 @@ def test_calibration_events():
 
 def test_trigger_times():
 
-    source = SimTelEventSource(input_url=calib_events_path)
+    source = SimTelEventSource(
+        input_url=calib_events_path,
+        focal_length_choice='nominal',
+    )
     t0 = Time("2020-05-06T15:30:00")
     t1 = Time("2020-05-06T15:40:00")
 
@@ -209,7 +228,10 @@ def test_trigger_times():
 
 
 def test_true_image():
-    with SimTelEventSource(input_url=calib_events_path) as reader:
+    with SimTelEventSource(
+        input_url=calib_events_path,
+        focal_length_choice='nominal',
+    ) as reader:
 
         for event in reader:
             for tel in event.simulation.tel.values():
@@ -218,7 +240,10 @@ def test_true_image():
 
 def test_instrument():
     """Test if same telescope types share a single instance of CameraGeometry"""
-    source = SimTelEventSource(input_url=gamma_test_large_path)
+    source = SimTelEventSource(
+        input_url=gamma_test_large_path,
+        focal_length_choice='nominal',
+    )
     subarray = source.subarray
     assert subarray.tel[1].optics.num_mirrors == 1
 
@@ -278,39 +303,36 @@ def test_apply_simtel_r1_calibration_2_channel():
     assert r1_waveforms[1, 0] == (r0_waveforms[0, 1, 0] - ped[0, 1]) * dc_to_pe[0, 1]
 
 
-def test_effective_focal_length():
-    test_file_url = (
-        "https://github.com/cta-observatory/pyeventio/raw/master/tests"
-        "/resources/prod4_pixelsettings_v3.gz"
-    )
-    test_file = download_file(test_file_url)
+def test_focal_length_choice():
+    # this file does not contain the effective focal length
+    with pytest.raises(RuntimeError):
+        SimTelEventSource(gamma_test_large_path)
 
-    focal_length_nominal = 0
-    focal_length_effective = 0
+    with pytest.raises(RuntimeError):
+        SimTelEventSource(gamma_test_large_path, focal_length_choice='effective')
 
-    with SimTelEventSource(
-        input_url=test_file, focal_length_choice="nominal"
-    ) as source:
-        subarray = source.subarray
-        focal_length_nominal = subarray.tel[1].optics.equivalent_focal_length
+    s = SimTelEventSource(gamma_test_large_path, focal_length_choice='nominal')
+    assert s.subarray.tel[1].optics.equivalent_focal_length == 28 * u.m
 
-    with SimTelEventSource(
-        input_url=test_file, focal_length_choice="effective"
-    ) as source:
-        subarray = source.subarray
-        focal_length_effective = subarray.tel[1].optics.equivalent_focal_length
+    # this file does
+    s = SimTelEventSource(prod5b_path, focal_length_choice='effective')
+    assert u.isclose(s.subarray.tel[1].optics.equivalent_focal_length, 29.3 * u.m, atol=0.05 * u.m)
+    # check guessing of the name is not affected by focal length choice
+    assert str(s.subarray.tel[1]) == 'LST_LST_LSTCam'
+
+    s = SimTelEventSource(prod5b_path, focal_length_choice='nominal')
+    assert u.isclose(s.subarray.tel[1].optics.equivalent_focal_length, 28.0 * u.m, atol=0.05 * u.m)
+    # check guessing of the name is not affected by focal length choice
+    assert str(s.subarray.tel[1]) == 'LST_LST_LSTCam'
 
-    assert focal_length_nominal > 0
-    assert focal_length_effective > 0
-    assert focal_length_nominal != focal_length_effective
 
 
 def test_only_config():
     config = Config()
-    config.SimTelEventSource.input_url = gamma_test_large_path
+    config.SimTelEventSource.input_url = prod5b_path
 
     s = SimTelEventSource(config=config)
-    assert s.input_url == Path(gamma_test_large_path).absolute()
+    assert s.input_url == Path(prod5b_path).absolute()
 
 
 def test_calibscale_and_calibshift(prod5_gamma_simtel_path):
@@ -355,11 +377,17 @@ def test_calibscale_and_calibshift(prod5_gamma_simtel_path):
 
 def test_true_image_sum():
     # this file does not contain true pe info
-    with SimTelEventSource(gamma_test_large_path) as s:
+    with SimTelEventSource(
+        gamma_test_large_path,
+        focal_length_choice='nominal',
+    ) as s:
         e = next(iter(s))
         assert np.all(np.isnan(sim.true_image_sum) for sim in e.simulation.tel.values())
 
-    with SimTelEventSource(calib_events_path) as s:
+    with SimTelEventSource(
+        calib_events_path,
+        focal_length_choice='nominal',
+    ) as s:
         e = next(iter(s))
 
         true_image_sums = {}
@@ -371,8 +399,10 @@ def test_true_image_sum():
 
     # check it also works with allowed_tels, since the values
     # are stored in a flat array in simtel
-    with SimTelEventSource(calib_events_path, allowed_tels={2, 3}) as s:
+    with SimTelEventSource(
+        calib_events_path, allowed_tels={2, 3},
+        focal_length_choice='nominal',
+    ) as s:
         e = next(iter(s))
-
         assert e.simulation.tel[2].true_image_sum == true_image_sums[2]
         assert e.simulation.tel[3].true_image_sum == true_image_sums[3]
diff --git a/ctapipe/reco/tests/test_HillasReconstructor.py b/ctapipe/reco/tests/test_HillasReconstructor.py
index 7ee4f1ad0c5..0b594cab952 100644
--- a/ctapipe/reco/tests/test_HillasReconstructor.py
+++ b/ctapipe/reco/tests/test_HillasReconstructor.py
@@ -197,11 +197,11 @@ def test_reconstruction_against_simulation(subarray_and_event_gamma_off_axis_500
 )
 def test_CameraFrame_against_TelescopeFrame(filename):
 
-    input_file = get_dataset_path(
-        "gamma_divergent_LaPalma_baseline_20Zd_180Az_prod3_test.simtel.gz"
-    )
+    input_file = get_dataset_path(filename)
+        # "gamma_divergent_LaPalma_baseline_20Zd_180Az_prod3_test.simtel.gz"
+    # )
 
-    source = SimTelEventSource(input_file, max_events=10)
+    source = SimTelEventSource(input_file, max_events=10, focal_length_choice="nominal")
 
     # too few events survive for this test with the defautl quality criteria,
     # use less restrictive ones
diff --git a/ctapipe/reco/tests/test_reconstruction_methods.py b/ctapipe/reco/tests/test_reconstruction_methods.py
index 1989e3962e8..ec99c7488bd 100644
--- a/ctapipe/reco/tests/test_reconstruction_methods.py
+++ b/ctapipe/reco/tests/test_reconstruction_methods.py
@@ -30,7 +30,7 @@ def test_reconstructors(reconstructors):
         "gamma_LaPalma_baseline_20Zd_180Az_prod3b_test.simtel.gz"
     )
 
-    source = EventSource(filename, max_events=10)
+    source = EventSource(filename, max_events=10, focal_length_choice="nominal")
     subarray = source.subarray
     calib = CameraCalibrator(source.subarray)
     image_processor = ImageProcessor(source.subarray)
diff --git a/ctapipe/tools/tests/test_process.py b/ctapipe/tools/tests/test_process.py
index d8f1a4b88ec..c9f4fbb5459 100644
--- a/ctapipe/tools/tests/test_process.py
+++ b/ctapipe/tools/tests/test_process.py
@@ -213,6 +213,7 @@ def test_stage_2_from_simtel(tmp_path):
                 f"--output={output}",
                 "--max-events=5",
                 "--overwrite",
+                "--SimTelEventSource.focal_length_choice=nominal",
             ],
             cwd=tmp_path,
         )
@@ -288,6 +289,7 @@ def test_training_from_simtel(tmp_path):
                 f"--output={output}",
                 "--max-events=5",
                 "--overwrite",
+                "--SimTelEventSource.focal_length_choice=nominal",
             ],
             cwd=tmp_path,
         )
diff --git a/ctapipe/tools/tests/test_tools.py b/ctapipe/tools/tests/test_tools.py
index f906213b40d..ebf74a751a1 100644
--- a/ctapipe/tools/tests/test_tools.py
+++ b/ctapipe/tools/tests/test_tools.py
@@ -13,6 +13,7 @@
 
 GAMMA_TEST_LARGE = get_dataset_path("gamma_test_large.simtel.gz")
 LST_MUONS = get_dataset_path("lst_muons.simtel.zst")
+PROD5B_PATH = get_dataset_path("gamma_20deg_0deg_run2___cta-prod5-paranal_desert-2147m-Paranal-dark_cone10-100evts.simtel.zst")
 
 
 def test_muon_reconstruction_simtel(tmp_path):
@@ -25,6 +26,7 @@ def test_muon_reconstruction_simtel(tmp_path):
             argv=[
                 f"--input={LST_MUONS}",
                 f"--output={muon_simtel_output_file}",
+                "--SimTelEventSource.focal_length_choice=nominal",
                 "--overwrite",
             ],
             cwd=tmp_path,
@@ -71,7 +73,12 @@ def test_display_dl1(tmp_path, dl1_image_file, dl1_parameters_file):
     # test simtel
     assert (
         run_tool(
-            DisplayDL1Calib(), argv=["--max-events=1", "--telescope=11"], cwd=tmp_path
+            DisplayDL1Calib(),
+            argv=[
+                "--max-events=1", "--telescope=11",
+                "--SimTelEventSource.focal_length_choice=nominal",
+            ],
+            cwd=tmp_path
         )
         == 0
     )
@@ -125,7 +132,7 @@ def test_dump_triggers(tmp_path):
 
     sys.argv = ["dump_triggers"]
     outfile = tmp_path / "triggers.fits"
-    tool = DumpTriggersTool(infile=GAMMA_TEST_LARGE, outfile=str(outfile))
+    tool = DumpTriggersTool(infile=PROD5B_PATH, outfile=str(outfile))
 
     assert run_tool(tool, cwd=tmp_path) == 0
 
@@ -139,18 +146,18 @@ def test_dump_instrument(tmp_path):
     sys.argv = ["dump_instrument"]
     tool = DumpInstrumentTool()
 
-    assert run_tool(tool, [f"--input={GAMMA_TEST_LARGE}"], cwd=tmp_path) == 0
+    assert run_tool(tool, [f"--input={PROD5B_PATH}"], cwd=tmp_path) == 0
     assert (tmp_path / "FlashCam.camgeom.fits.gz").exists()
 
     assert (
-        run_tool(tool, [f"--input={GAMMA_TEST_LARGE}", "--format=ecsv"], cwd=tmp_path)
+        run_tool(tool, [f"--input={PROD5B_PATH}", "--format=ecsv"], cwd=tmp_path)
         == 0
     )
 
     assert (tmp_path / "MonteCarloArray.optics.ecsv").exists()
 
     assert (
-        run_tool(tool, [f"--input={GAMMA_TEST_LARGE}", "--format=hdf5"], cwd=tmp_path)
+        run_tool(tool, [f"--input={PROD5B_PATH}", "--format=hdf5"], cwd=tmp_path)
         == 0
     )
     assert (tmp_path / "subarray.h5").exists()
diff --git a/ctapipe/utils/datasets.py b/ctapipe/utils/datasets.py
index 42f187f2b82..71ba61485ed 100644
--- a/ctapipe/utils/datasets.py
+++ b/ctapipe/utils/datasets.py
@@ -28,7 +28,7 @@
 __all__ = ["get_dataset_path", "find_in_path", "find_all_matching_datasets"]
 
 
-DEFAULT_URL = "http://cccta-dataserver.in2p3.fr/data/ctapipe-extra/v0.3.3/"
+DEFAULT_URL = "http://cccta-dataserver.in2p3.fr/data/ctapipe-extra/v0.3.4/"
 
 
 def get_searchpath_dirs(searchpath=os.getenv("CTAPIPE_SVC_PATH"), url=DEFAULT_URL):
diff --git a/docs/examples/InstrumentDescription.ipynb b/docs/examples/InstrumentDescription.ipynb
index f70a901ce53..dbefaa51c48 100644
--- a/docs/examples/InstrumentDescription.ipynb
+++ b/docs/examples/InstrumentDescription.ipynb
@@ -21,8 +21,7 @@
     "from ctapipe.io import EventSource\n",
     "import numpy as np\n",
     "\n",
-    "#filename = get_dataset_path(\"gamma_test_large.simtel.gz\") # try this one as well\n",
-    "filename = get_dataset_path(\"gamma_test_large.simtel.gz\")  \n",
+    "filename = get_dataset_path(\"gamma_prod5.simtel.zst\")  \n",
     "\n",
     "with EventSource(filename, max_events=1) as source:\n",
     "    subarray = source.subarray"
@@ -359,7 +358,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -373,7 +372,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.10"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,
diff --git a/docs/tutorials/calibrated_data_exploration.ipynb b/docs/tutorials/calibrated_data_exploration.ipynb
index d2c5bddf28d..725d29d84a1 100644
--- a/docs/tutorials/calibrated_data_exploration.ipynb
+++ b/docs/tutorials/calibrated_data_exploration.ipynb
@@ -48,7 +48,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "filename = get_dataset_path(\"gamma_test.simtel.gz\")\n",
+    "filename = get_dataset_path(\"gamma_prod5.simtel.zst\")\n",
     "source = EventSource(filename, max_events=2)\n",
     "\n",
     "for event in source:\n",
@@ -85,7 +85,9 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "scrolled": false
+   },
    "outputs": [],
    "source": [
     "print(event.r1)"
@@ -351,11 +353,18 @@
     "ad.values = hit_pattern\n",
     "ad.add_labels()\n"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -369,7 +378,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.10"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,
diff --git a/docs/tutorials/coordinates_example.ipynb b/docs/tutorials/coordinates_example.ipynb
index 6f6d2d47042..429efc7ed15 100644
--- a/docs/tutorials/coordinates_example.ipynb
+++ b/docs/tutorials/coordinates_example.ipynb
@@ -90,11 +90,11 @@
    },
    "outputs": [],
    "source": [
-    "filename = get_dataset_path(\"gamma_test_large.simtel.gz\")\n",
-    "source = EventSource(filename, max_events=4)\n",
+    "filename = get_dataset_path(\"gamma_prod5.simtel.zst\")\n",
+    "source = EventSource(filename)\n",
     "\n",
     "events = [copy.deepcopy(event) for event in source]\n",
-    "event = events[3]\n",
+    "event = events[4]\n",
     "\n",
     "layout = set(source.subarray.tel_ids)  "
    ]
@@ -123,8 +123,8 @@
    },
    "outputs": [],
    "source": [
-    "print(f'Telescope with data: {event.r0.tel.keys()}')\n",
-    "tel_id = 2"
+    "print(f'Telescope with data: {event.r1.tel.keys()}')\n",
+    "tel_id = 3"
    ]
   },
   {
@@ -620,7 +620,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -634,7 +634,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.10"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,
diff --git a/docs/tutorials/ctapipe_handson.ipynb b/docs/tutorials/ctapipe_handson.ipynb
index d9ce8fd3760..68115dfd9f5 100644
--- a/docs/tutorials/ctapipe_handson.ipynb
+++ b/docs/tutorials/ctapipe_handson.ipynb
@@ -35,7 +35,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "path = utils.get_dataset_path(\"gamma_test_large.simtel.gz\")"
+    "path = utils.get_dataset_path(\"gamma_prod5.simtel.zst\")"
    ]
   },
   {
@@ -44,7 +44,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "source = EventSource(path, max_events=4)\n",
+    "source = EventSource(path, max_events=5)\n",
     "\n",
     "for event in source:\n",
     "    print(event.count, event.index.event_id, event.simulation.shower.energy)"
@@ -65,7 +65,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "event.r0"
+    "event.r1"
    ]
   },
   {
@@ -74,8 +74,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "for event in EventSource(path, max_events=4):\n",
-    "    print(event.count, event.r0.tel.keys())"
+    "for event in EventSource(path, max_events=5):\n",
+    "    print(event.count, event.r1.tel.keys())"
    ]
   },
   {
@@ -84,7 +84,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "event.r0.tel[2]"
+    "event.r0.tel[3]"
    ]
   },
   {
@@ -366,7 +366,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "for event in EventSource(path, max_events=4):\n",
+    "for event in EventSource(path, max_events=5):\n",
     "    calib(event) # fills in r1, dl0, and dl1\n",
     "    print(event.dl1.tel.keys())"
    ]
@@ -480,8 +480,8 @@
     "disp = CameraDisplay(tel.camera.geometry, image=cleaned)\n",
     "disp.cmap = plt.cm.coolwarm\n",
     "disp.add_colorbar()\n",
-    "plt.xlim(-1.0,0)\n",
-    "plt.ylim(0,1.0)"
+    "plt.xlim(0.5, 1.0)\n",
+    "plt.ylim(-1.0, 0.0)"
    ]
   },
   {
@@ -503,8 +503,8 @@
     "disp = CameraDisplay(tel.camera.geometry, image=cleaned)\n",
     "disp.cmap = plt.cm.coolwarm\n",
     "disp.add_colorbar()\n",
-    "plt.xlim(-1.0,0)\n",
-    "plt.ylim(0,1.0)\n",
+    "plt.xlim(0.5, 1.0)\n",
+    "plt.ylim(-1.0, 0.0)\n",
     "disp.overlay_moments(params, color='white', lw=2)"
    ]
   },
@@ -557,8 +557,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "data = utils.get_dataset_path(\"gamma_test_large.simtel.gz\") \n",
-    "source = EventSource(data, allowed_tels=[1,2,3,4],  max_events=10) # remove the max_events limit to get more stats"
+    "data = utils.get_dataset_path(\"gamma_prod5.simtel.zst\") \n",
+    "source = EventSource(data) # remove the max_events limit to get more stats"
    ]
   },
   {
@@ -573,7 +573,8 @@
     "    for tel_id, tel_data in event.dl1.tel.items():\n",
     "        tel = source.subarray.tel[tel_id]\n",
     "        mask = tailcuts_clean(tel.camera.geometry, tel_data.image)\n",
-    "        params = hillas_parameters(tel.camera.geometry[mask], tel_data.image[mask])"
+    "        if np.count_nonzero(mask) > 0:\n",
+    "            params = hillas_parameters(tel.camera.geometry[mask], tel_data.image[mask])"
    ]
   },
   {
@@ -645,20 +646,13 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "If you do this yourself, loop over more events to get better statistics"
+    "If you do this yourself, chose a larger file to loop over more events to get better statistics"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -672,7 +666,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.8"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,
diff --git a/docs/tutorials/ctapipe_overview.ipynb b/docs/tutorials/ctapipe_overview.ipynb
index 0c4b98f18e2..64ae83a4cdd 100644
--- a/docs/tutorials/ctapipe_overview.ipynb
+++ b/docs/tutorials/ctapipe_overview.ipynb
@@ -222,11 +222,11 @@
     "from ctapipe.io import EventSource\n",
     "from ctapipe.utils.datasets import get_dataset_path\n",
     "\n",
-    "input_url = get_dataset_path('gamma_test_large.simtel.gz')\n",
+    "input_url = get_dataset_path('gamma_prod5.simtel.zst')\n",
     "\n",
     "# EventSource() automatically detects what kind of file we are giving it,\n",
     "# if already supported by ctapipe\n",
-    "source = EventSource(input_url, max_events=49)\n",
+    "source = EventSource(input_url, max_events=5)\n",
     "\n",
     "print(type(source))"
    ]
@@ -351,7 +351,7 @@
    },
    "outputs": [],
    "source": [
-    "tel_id = 4"
+    "tel_id = 130"
    ]
   },
   {
@@ -425,12 +425,12 @@
    },
    "outputs": [],
    "source": [
-    "# unoptimized cleaning levels, copied from \n",
-    "# https://github.com/tudo-astroparticlephysics/cta_preprocessing\n",
+    "# unoptimized cleaning levels\n",
     "cleaning_level = {\n",
-    "    'ASTRICam': (5, 7, 2),  # (5, 10)?\n",
-    "    'LSTCam': (3.5, 7.5, 2),  # ?? (3, 6) for Abelardo...\n",
-    "    'FlashCam': (4, 8, 2),  # there is some scaling missing?\n",
+    "    'CHEC': (2, 4, 2),\n",
+    "    'LSTCam': (3.5, 7, 2),\n",
+    "    'FlashCam': (3.5, 7, 2), \n",
+    "    'NectarCam': (4, 8, 2), \n",
     "}"
    ]
   },
@@ -675,19 +675,21 @@
     "            \"picture_threshold_pe\": [\n",
     "                (\"type\", \"LST_LST_LSTCam\", 7.5),\n",
     "                (\"type\", \"MST_MST_FlashCam\", 8),\n",
-    "                (\"type\", \"SST_ASTRI_ASTRICam\", 7),\n",
+    "                (\"type\", \"MST_MST_NectarCam\", 8),\n",
+    "                (\"type\", \"SST_ASTRI_CHEC\", 7),\n",
     "            ],\n",
     "            \"boundary_threshold_pe\": [\n",
     "                (\"type\", \"LST_LST_LSTCam\", 5),\n",
     "                (\"type\", \"MST_MST_FlashCam\", 4),\n",
-    "                (\"type\", \"SST_ASTRI_ASTRICam\", 4),\n",
+    "                (\"type\", \"MST_MST_NectarCam\", 4),\n",
+    "                (\"type\", \"SST_ASTRI_CHEC\", 4),\n",
     "            ]\n",
     "            \n",
     "        }\n",
     "    }\n",
     "})\n",
     "\n",
-    "input_url = get_dataset_path('gamma_test_large.simtel.gz')\n",
+    "input_url = get_dataset_path('gamma_prod5.simtel.zst')\n",
     "source = EventSource(input_url)\n",
     "\n",
     "calibrator = CameraCalibrator(subarray=source.subarray)\n",
@@ -809,8 +811,8 @@
     ")\n",
     "\n",
     "plt.legend()\n",
-    "plt.xlim(-400, 400)\n",
-    "plt.ylim(-400, 400)"
+    "# plt.xlim(-400, 400)\n",
+    "# plt.ylim(-400, 400)"
    ]
   },
   {
diff --git a/docs/tutorials/raw_data_exploration.ipynb b/docs/tutorials/raw_data_exploration.ipynb
index 6c2d63207f8..884fd025696 100644
--- a/docs/tutorials/raw_data_exploration.ipynb
+++ b/docs/tutorials/raw_data_exploration.ipynb
@@ -24,11 +24,12 @@
    "outputs": [],
    "source": [
     "from ctapipe.utils import get_dataset_path\n",
-    "from ctapipe.io import EventSource, EventSeeker\n",
+    "from ctapipe.io import EventSource\n",
     "from ctapipe.visualization import CameraDisplay\n",
     "from ctapipe.instrument import CameraGeometry\n",
     "from matplotlib import pyplot as plt\n",
     "from astropy import units as u\n",
+    "\n",
     "%matplotlib inline"
    ]
   },
@@ -47,8 +48,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "source = EventSource(get_dataset_path(\"gamma_test_large.simtel.gz\"), max_events=100, back_seekable=True)\n",
-    "seeker = EventSeeker(source)"
+    "source = EventSource(get_dataset_path(\"gamma_prod5.simtel.zst\"), max_events=5)"
    ]
   },
   {
@@ -66,8 +66,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "event = seeker.get_event_index(3)  # get 3rd event\n",
-    "event"
+    "# so we can advance through events one-by-one\n",
+    "event_iterator = iter(source)\n",
+    "\n",
+    "event = next(event_iterator)"
    ]
   },
   {
@@ -83,7 +85,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "print(repr(event.r0))"
+    "event.r0"
    ]
   },
   {
@@ -115,7 +117,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "note that the event has 2 telescopes in it: 38,40... Let's try the next one:"
+    "note that the event has 3 telescopes in it: Let's try the next one:"
    ]
   },
   {
@@ -124,7 +126,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "event = seeker.get_event_index(5) # get the next event\n",
+    "event = next(event_iterator)\n",
     "print(event.r0.tel.keys())"
    ]
   },
@@ -132,7 +134,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "now, we have a larger event with many telescopes... Let's look at the data from **CT7**:"
+    "now, we have a larger event with many telescopes... Let's look at one of them:"
    ]
   },
   {
@@ -141,7 +143,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "teldata = event.r0.tel[15]\n",
+    "teldata = event.r0.tel[26]\n",
     "print(teldata)\n",
     "teldata"
    ]
@@ -419,7 +421,9 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "scrolled": false
+   },
    "outputs": [],
    "source": [
     "for tel in event.r0.tel.keys():\n",
@@ -488,7 +492,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -502,7 +506,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.8"
+   "version": "3.8.13"
   }
  },
  "nbformat": 4,
diff --git a/docs/tutorials/theta_square.ipynb b/docs/tutorials/theta_square.ipynb
index b141c58626e..91191ae275a 100644
--- a/docs/tutorials/theta_square.ipynb
+++ b/docs/tutorials/theta_square.ipynb
@@ -73,7 +73,10 @@
    },
    "outputs": [],
    "source": [
-    "source = EventSource(\"dataset://gamma_test_large.simtel.gz\", allowed_tels={1, 2, 3, 4})\n",
+    "source = EventSource(\n",
+    "    \"dataset://gamma_prod5.simtel.zst\",\n",
+    "#     allowed_tels={1, 2, 3, 4},\n",
+    ")\n",
     "\n",
     "subarray = source.subarray\n",
     "\n",