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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.

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Case of Bartenheim-la-Chaussée, on July 19, 2007:

Case number:



Someone reported to the Alsatian ufology group SPICA that on Thursday, July 19, 2007, while walking with his dog like every night in the last 5 years before bedtime, at the same place in Bartenheim-la-Chaussée, looking at the sky and stars as almost every night, he discovered two or three oval lights moving at the level of the few clouds.

These discs of a rather peculiar light, of low luminosity that he would qualify as "pastel", moved very fast, forming regular ellipses. The direction of each unit often stayed the same, but it changed from time to time, and sometimes stopped to meet one another in a stationary position before starting up again a moment later.

As his eyes became used to this particular clarity, it discovered other, to finally count about ten of them, were moving in all directions.

He watched this for a quarter of an hour before going home, and still perceived their spinning when he walked through the door of his house.

He asked for clarification, and SPICA answered in their bulletin for January 2008 where this was reported: "A nightclub SkyTracer".


Temporal data:

Date: July 19, 2007
Time: Night.
Duration: 15 minutes.
First known report date: January 2008
Reporting delay: 6 months.

Geographical data:

Department: Haut-Rhin
City: Bartenheim-la-Chaussée
Place: Walking the dog in Bartenheim-la-Chaussée, UFO in the sky.
Latitude: 47.368
Longitude: 7.513
Uncertainty ratio: 1 km

Witnesses data:

Number of alleged witnesses: 1
Number of known witnesses: 1
Number of named witnesses: 0
Witness(es) ages: ?
Witness(es) types: ?

Ufology data:

Reporting channel: SPICA local ufology bulletin.
Type of location: Walking the dog in familiar place, UFO in the sky.
Visibility conditions: Night
UFO observed: Yes
UFO arrival observed: No
UFO departure observed: No
Entities: No
Photographs: No.
Sketch(s) by witness(es): No.
Sketch(es) approved by witness(es): No.
Witness(es) feelings: Puzzled.
Witnesses interpretation: Dos not know.


Hynek: NL
ALSACAT: Skytracers.



Bartenheim La Chaussee (68) Thursday, July 19, 2007-12-20

Source SPICA

One evening, precisely on Thursday, July 19, 2007, while I was walking like every night for 5 years at the same location (BARTENHEIM LA CHAUSSEE) before going to bed, with my dog, while like every night or almost I watched the sky and the stars, I discover 2 or 3 oval lights moving at the height of the few clouds. These discs of a somehow peculiar light, of low luminosity I would call "pastel" moved very quickly by forming regular ellipses. The direction of each unit often remained the same, but it changed from time to time, and sometimes stopped to meet one another in a stationary position before starting up again a moment later.

As my eyes were getting used to this particular clarity I discovered others to finally count a little ten of them that were moving in all directions. I watched them for a quarter of an hour before returning and I still could see the whirling through the door of my house.

Do you have an idea to enlighten me about this?

SPICA Explanation: A discotheque Skyroser [sic, "SkyTracer"]


City Date and hour of observation General shape
General color
BARTENHEIM-LA-CHAUSSEE Thursday 19 July 2007 Circular, round or disc (2D)
Artificial luminous reflection (projector)
Artificial luminous reflection (projector)


This is probably one of the best descriptions of disco skytracers by a witness I found. He does not know what it is, but he described the event clearly enough so that there is no doubt about it.

He was not the first to be puzzled in that area, for good reason: there is a large discotheque in Bartenheim, "Discopolis" - actually "Planet Discopolis", formerly "Macumba" then "Loisirs Palace", 5, rue Robert Schumann, 68870 Bartenheim. It uses Skytracers, I have already seen them at work.

For the record, in the 1990's, the disco showed in the entrance in a shop window, a dummy representing "the Roswell alien."

About "Skytracers":

One sometimes call them "discotheque lasers", it is often so in the regional Pres, as a cause of UFO sightings. They are actually not lasers but projectors of ordinary light.

The purpose of these Skytracers is to get attention from far away, up to miles away. Lasers are mostly effective on location, inside a nightclub or on a concert place.

Their light can be white, but it can also have a green, blue, red, yellow hue... Motors are used to move the projections on 1, 2 or 3 axis. By software, they can be programmed to perform sequences of more or less repetitive figures; as witnesses often report.

When there is vapor in the air from the ground up, the Skytracer produces a beam of light, fixed or mobile.

It can produce the impression of a "luminous cigar."

But id a low cloud layer tops a mass of dry air on the ground, there is no visible beam, one sees the projection of the beam on the bottom of the clouds. It is mostly in such conditions that people sometimes are unable to recognize projectors.

With several networked and programmed Skytracers, it is possible de produce shows of the "flying saucer" or "flying saucers formation" kind.



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 July 22, 2015 Creation, [spa1], [spa2].
1.0 Patrick Gross July 22, 2015 First published.

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This page was last updated on July 22, 2015.