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ALSACAT is my comprehensive catalog of UFO sighting reports in Alsace, the region is the North-East of France, whether they are "explained" or "unexplained".

The ALSACAT catalog is made of case files with a case number, summary, quantitative information (date, location, number of witnesses...), classifications, all sources mentioning the case with their references, a discussion of the case in order to evaluate its causes, and a history of the changes made to the file. A general index and thematic sub-catalogs give access to these Alsatian case files.

Case of Dieffenbach-au-Val, in the 1990's:

Case number:



Someone had reported to the UFO web forum "R.I.O." an observation in the evening between 11:00 p.m. and 01:00 a.m., around 1990 or 1993, near Dieffenbach-au-Val in the Bas-Rhin.

Returning from an evening party with a friend, they had chatted outside the latter's home, and then both watched in silence the mountain in front of them, the rock of the Cuckoo in Dieffenbach.

In a logging hole, the witness saw a white object go down, identifying it as a motorcycle headlight, and he thought there was "a crackpot who makes a motorcycle night descent."

But this "motorcycle" traveled about 500 meters from the top of the mountain to roughly its 2/3 in about 4 or 5 seconds and then left in the sky at right angle relative to its initial descent trajectory of 45°, with lightning-speed acceleration, disappearing into the night after a half second.

Flabbergasted, the witness asked his friend what he had seen it and the latter described the same thing, though they had not spoken during the observation. This strengthened the witness to the fact that what they saw was not a hallucination.


Temporal data:

Date: In the 1990's
Time: Between 11:00 p.m. and 01:00 a.m.
Duration: 5 to 6 seconds.
First known report date: 2005
Reporting delay: 12 years.

Geographical data:

Department: Bas-Rhin
City: Dieffenbach-au-Val
Place: Outside home, UFO on mountain slope and in the sky.
Latitude: 48.315
Longitude: 7.335
Uncertainty ratio: 5 km

Witnesses data:

Number of alleged witnesses: 2
Number of known witnesses: 1
Number of named witnesses: 0
Witness(es) ages: Teenagers or adults.
Witness(es) types: ?

Ufology data:

Reporting channel: By the web to the UFO forum "R.I.O.".
Type of location: Outside home, UFO on mountain slope and in the sky.
Visibility conditions: Night
UFO observed: Yes
UFO arrival observed: ?
UFO departure observed: Yes
Entities: No
Photographs: No.
Sketch(s) by witness(es): No.
Sketch(es) approved by witness(es): No.
Witness(es) feelings: Puzzled.
Witnesses interpretation: Not an hallucination, not a motorbike headlight.


Hynek: NL
ALSACAT: Possible helicopter.



1993 Dieffenbach 67 France

Source : RIO

It was about a dozen years ago, one evening with a friend, we saw something really surprising:

It was late at night, between 11pm and 1am, on the way home from a party, we discussed outside his home, and suddenly we both watch in silence the mountain in front of us (the rock of the Cuckoo Dieffenbach (67) and in a logging hole, I see a white object that I identify as a motorcycle headlight go down, and I think there's a crackpot who makes a night descent by motorcycle. The problem is that this "motorcycle" makes + - 500 m (from the top of the mountain to its 2/3 + -) in about 4 or 5 seconds and then goes up in the air at right angle from its original path (a descent at 45 °) with lightning-speed acceleration and disappears after 1/2 second in the night. Flabbergasted, I ask my friend what he saw and he describes the same thing to me as what I have described, but without telling him. What comforts me to the fact that what we saw was not a hallucination.


City Date and hour of observation General shape
General color
DIEFFENBACH Years 1990 at 11:00 p.m. Circular, round or disc (2D)
Unsolved -lack of info


The "rocher du Coucou" ("rock of the Cuckoo") in the Altenberg, in the "Val-de-Villé" is 856 meters above sea level on the territory of the municipality of Neubois, at 173° and 2.7 kilometers in a straight line from the center of Dieffenbach-au-val. Its summit is visible from far away. There is a television transmitting antenna on the top, paths and sources on its slopes but no paved road.

view to the rocher du Coucou
(the mountain top on the right)
from Dieffenbach.

It is however in no way certain that the witnesses were in Dieffenbach, since it is the rock and not themselves that they locate there.

view to the rocher du Coucou
(the mountain top on the right) from Thanvillé.

There is indeed a logging gap on its slope, on the valley of Val-de-Villé side.

A path from the top to 2/3 of its slope is actually equivalent to about 500 meters. Traveled in 4-5 seconds, it gives a speed of 100 to 125 m/s or 360-450 km/h assuming of course that the thing was on the ground on the slope.

Apart from a possible alien craft, the only scenario I see is that of a helicopter that would have flown from the top, down the slope, then veering off to the sky thus hiding its headlight(s). The viewing distance of a few kilometers at least could have masked its engine noise.


Possible helicopter.

Sources references:

* = Source is available to me.
? = Source I am told about but could not get so far. Help needed.

File history:


Main author: Patrick Gross
Contributors: None
Reviewers: None
Editor: Patrick Gross

Changes history:

Version: Create/changed by: Date: Description:
0.1 Patrick Gross August 27, 2015 Creation, [spa1], [spa2].
1.0 Patrick Gross August 27, 2015 First published.

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This page was last updated on August 27, 2015.