Within Stars
How to Check a Flashing Light Against the Sky
A sky map using the exact date, time, place and direction can often test whether a flashing light was a known star or planet.
On this page
- The details a sighting report needs
- Using bearing and altitude without overclaiming
- Common errors when checking later
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Introduction
Many reports of colour-changing or flashing lights can be checked against the known sky before any more exotic explanation is considered. A sky-map reconstruction uses the exact date, time, location and viewing direction from a sighting report to determine whether a bright star or planet occupied the same position. Because stars and planets follow predictable paths, a surprisingly large number of reports can be tested after the fact if enough observational details were recorded. Modern planetarium software and online sky maps can recreate the sky for almost any place and time, allowing investigators to compare a witness’s description with known celestial objects. [Stellarium Web]stellarium-web.orgStellarium WebStellarium Web Online Star MapStellarium Web is a planetarium running in your web browser. It shows a realistic star map, j… [stellarium]stellarium.orgStellariumStellarium Astronomy SoftwareStellarium is a planetarium software that shows exactly what you see when you look up at the stars… For reports involving twinkling, colour changes or apparently stationary lights, this approach is especially valuable. A flashing light that seems unusual in memory may match the position of a bright star such as Sirius or a bright planet viewed low above the horizon. The strength of the check depends largely on the quality of the original observation record.
The Details a Sighting Report Needs
A sky-map check is only as good as the information supplied. The most useful reports include:
- Exact date and local time, preferably to the nearest minute.
- Observation location.
- Direction of the light.
- Approximate height above the horizon.
- Duration of the observation.
- Whether the object appeared fixed, drifting or rapidly moving.
- Weather and visibility conditions.
Time matters because the sky changes continuously. Stars rise and set, planets move relative to the stars, and even a difference of fifteen or twenty minutes can shift a celestial object’s apparent position noticeably. Sky-chart and planetarium systems allow investigators to recreate the sky for a specific location and moment, making precise timing far more valuable than a rough estimate. Sky & Telescope [Sky at Night Magazine]skyatnightmagazine.comstellarium astronomy planetarium software how to useHow to install and use Stellarium astronomy software17 Jul 2020 — In general use, if you want to display the sky for a specific date and…
Location is equally important. The sky seen from southern England is not identical to the sky seen from northern Scotland or southern Spain at the same moment. Modern planetarium software calculates positions from the observer’s coordinates and can show which stars, planets and other bright objects were visible. [Stellarium]stellarium.orgStellariumStellarium Astronomy SoftwareStellarium is a planetarium software that shows exactly what you see when you look up at the stars… [EuroVO]vo-for-education.oats.inaf.itFOR BEGINNERSStellarium is a free software that transforms your home computer in a planetarium. It calculates the positions of the Sun an…
Using Bearing and Altitude Without Overclaiming
The most useful directional information is a combination of bearing and altitude.
Bearing, often called azimuth in astronomy, is the compass direction of the light. Altitude is the angle above the horizon. Together they describe a position in the observer’s sky. The altitude-azimuth system is the standard method for locating visible objects relative to an observer’s position. [The Open University]open.eduThe Open University3.2 The Altitude-Azimuth systemThe Alt-Azimuth system of coordinates specifies the position of an object in terms of t…
In practice, witnesses rarely provide precise measurements. Instead, they might say:
- “Low in the south-west.”
- “Above the treeline.”
- “About halfway between the horizon and overhead.”
- “Just above the roof of a house.”
Even rough estimates can be useful. If a witness reports a flashing red-green-white light low in the south-west at 22:15, and a sky reconstruction shows a bright star at the same bearing and altitude, the match becomes a plausible explanation. If the nearest bright celestial object was forty degrees away, the identification becomes much less convincing.
However, investigators should avoid overclaiming. Human estimates of direction and height are often inaccurate, especially at night. A sky-map match is evidence of a possible identification, not automatic proof. The best cases are those where several factors agree simultaneously:
- Position matches.
- Brightness matches.
- Colour-changing behaviour matches.
- Apparent lack of movement matches.
- Observation duration is consistent with a celestial source.
When multiple elements align, the probability of a mistaken astronomical identification rises substantially. [Adler Planetarium]adlerplanetarium.orgAdler Planetarium How To Identify Planets In The Night SkyAdler PlanetariumHow To Identify Planets In The Night SkyMarch 17, 2025 — 17 Mar 2025 — The easiest way to pick out visible planets is to… [The Open University]open.eduThe Open University3.2 The Altitude-Azimuth systemThe Alt-Azimuth system of coordinates specifies the position of an object in terms of t…
Reconstructing the Sky Step by Step
Modern tools make retrospective checks relatively straightforward. Programs such as Stellarium and similar interactive sky maps allow users to enter a location and historical date and then view the sky exactly as it would have appeared from that point. [Stellarium Web]stellarium-web.orgStellarium WebStellarium Web Online Star MapStellarium Web is a planetarium running in your web browser. It shows a realistic star map, j… [stellarium]stellarium.orgStellariumStellarium Astronomy SoftwareStellarium is a planetarium software that shows exactly what you see when you look up at the stars… A typical reconstruction involves:
- Entering the observation location.
- Setting the reported date and time.
- Facing the reported direction.
- Comparing the reported altitude with visible bright objects.
- Checking whether a bright star or planet occupied the reported position.
If the witness described intense colour flashing, special attention should be paid to bright objects near the horizon. Atmospheric effects are strongest there, making stars appear more colourful and unstable than they do higher in the sky. A reconstructed sky can show whether a known bright object occupied exactly that part of the horizon at the relevant time. [Adler Planetarium]adlerplanetarium.orgAdler Planetarium How To Identify Planets In The Night SkyAdler PlanetariumHow To Identify Planets In The Night SkyMarch 17, 2025 — 17 Mar 2025 — The easiest way to pick out visible planets is to… [Stellarium Web]stellarium-web.orgStellarium WebStellarium Web Online Star MapStellarium Web is a planetarium running in your web browser. It shows a realistic star map, j…
Common Errors When Checking Later
Many failed identifications arise not because the method is flawed, but because the reconstruction uses incomplete or inaccurate information.
One common mistake is using the wrong time zone or forgetting daylight-saving adjustments. An hour’s error can place a celestial object in a significantly different position or even below the horizon. Sky-chart users are routinely warned that date and time settings must be handled carefully. [cupcakes and the cosmos]cupcakesandthecosmos.comcupcakes and the cosmosHow To Use A Star Chart | Cupcakes and the Cosmos BlogNovember 8, 2016 — 8 Nov 2016 — Learn how to use a star char…
Another problem is assuming the witness’s remembered direction was exact. People frequently remember a light as being “south” when it was actually south-west or west-south-west. A rigid reconstruction that treats memory as precise can wrongly eliminate a valid astronomical candidate.
A third error is checking only stars and ignoring planets. Bright planets can attract UFO reports because they appear unusually bright and can seem fixed in the sky. Although planets generally twinkle less than stars, atmospheric conditions near the horizon can still create noticeable visual effects. [Adler Planetarium]adlerplanetarium.orgAdler Planetarium How To Identify Planets In The Night SkyAdler PlanetariumHow To Identify Planets In The Night SkyMarch 17, 2025 — 17 Mar 2025 — The easiest way to pick out visible planets is to…
Investigators also sometimes overlook the local horizon. Hills, buildings and trees can hide or reveal celestial objects in ways not reflected by a simple sky map. A star visible from an open field may not have been visible from a built-up street, and vice versa.
Why Sky-Map Checks Matter for Colour-Changing Light Reports
Colour-changing lights often generate reports because the observer reasonably assumes that changing colours indicate a powered object. A sky-map reconstruction tests that assumption against known celestial positions. If a bright star or planet occupied the reported location, the observation may be explained by atmospheric effects combined with normal human distance and motion perception.
Importantly, the method does not dismiss the witness. The light was real. The question is whether its appearance resulted from a distant celestial source viewed through the atmosphere rather than a nearby structured object. By comparing a report with the reconstructed sky, investigators can separate many mistaken identifications from cases that require further examination. This makes sky-map checking one of the most practical and evidence-based tools available when assessing reports of flashing or colour-changing lights in the night sky. [Stellarium Web]stellarium-web.orgStellarium WebStellarium Web Online Star MapStellarium Web is a planetarium running in your web browser. It shows a realistic star map, j… [Sky & Telescope]skyandtelescope.orginteractive sky chartSky & TelescopeInteractive Sky Chart | Map Your Night SkyWhat's in your night sky tonight? Open our interactive sky chart to create a cus…
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Endnotes
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Source: stellarium-web.org
Link: https://stellarium-web.org/Source snippet
Stellarium WebStellarium Web Online Star MapStellarium Web is a planetarium running in your web browser. It shows a realistic star map, j...
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Source: stellarium.org
Link: https://stellarium.org/Source snippet
StellariumStellarium Astronomy SoftwareStellarium is a planetarium software that shows exactly what you see when you look up at the stars...
-
Source: open.edu
Link: https://www.open.edu/openlearn/mod/oucontent/view.php?id=114762§ion=3.2Source snippet
The Open University3.2 The Altitude-Azimuth systemThe Alt-Azimuth system of coordinates specifies the position of an object in terms of t...
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Source: youtube.com
Link: http://www.youtube.com/watch?v=1VrcHxm4tEMSource snippet
Stellarium with Sky Surveys: Astrophotography Game-Changer...
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Source: youtube.com
Title: Stellarium with Sky Surveys: Astrophotography Game-Changer!
Link: http://www.youtube.com/watch?v=5ddQDw-COX4Source snippet
How to use Stellarium to identify night [sky objects]({{ 'sky-objects/' | relative_url }}) How to use Stellarium-Web Cernan Earth and Space Center...
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Source: skyandtelescope.org
Title: interactive sky chart
Link: https://skyandtelescope.org/stargazing-and-observing/interactive-stargazing-tools/interactive-sky-chart/Source snippet
Sky & TelescopeInteractive Sky Chart | Map Your Night SkyWhat's in your night sky tonight? Open our interactive sky chart to create a cus...
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Source: skyatnightmagazine.com
Title: stellarium astronomy planetarium software how to use
Link: https://www.skyatnightmagazine.com/advice/skills/stellarium-astronomy-planetarium-software-how-to-useSource snippet
How to install and use Stellarium astronomy software17 Jul 2020 — In general use, if you want to display the sky for a specific date and...
-
Source: vo-for-education.oats.inaf.it
Link: https://vo-for-education.oats.inaf.it/use_cases/en_cosadie_19_stellarium.pdfSource snippet
FOR BEGINNERSStellarium is a free software that transforms your home computer in a planetarium. It calculates the positions of the Sun an...
-
Source: adlerplanetarium.org
Title: Adler Planetarium How To Identify Planets In The Night Sky
Link: https://www.adlerplanetarium.org/blog/how-to-identify-planets/Source snippet
Adler PlanetariumHow To Identify Planets In The Night SkyMarch 17, 2025 — 17 Mar 2025 — The easiest way to pick out visible planets is to...
Published: March 17, 2025
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Source: cupcakesandthecosmos.com
Link: https://www.cupcakesandthecosmos.com/2016/11/how-to-use-a-star-chart/Source snippet
cupcakes and the cosmosHow To Use A Star Chart | Cupcakes and the Cosmos BlogNovember 8, 2016 — 8 Nov 2016 — Learn how to use a star char...
Published: November 8, 2016
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Source: play.google.com
Link: https://play.google.com/store/apps/details?hl=en&id=com.noctuasoftware.stellarium_freeSource snippet
Star Map - Apps on Google PlayStellarium - Star Map is a planetarium app that shows exactly what you see when you look up at the stars. I...
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Source: play.google.com
Link: https://play.google.com/store/apps/details?hl=en&id=com.google.android.stardroidSource snippet
Map - Apps on Google PlaySky Map helps you identify stars, planets, nebulae, and constellations in real-time. Originally developed as Goo...
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Source: youtube.com
Title: Stellarium Planetarium Software
Link: https://www.youtube.com/watch?v=fRFligT-C8wSource snippet
February 2012 Jupiter...Let's play Stellarium! This is a free open source planetarium software available for Windows, Mac and Linux. It...
Published: February 2012
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Source: stellarium-labs.com
Link: https://stellarium-labs.com/blog/gridsandlines/Source snippet
In this article, we'll have a quick look at each one and discuss...Read more...
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Source: astronomia.edu.uy
Link: https://www.astronomia.edu.uy/CTE2/stellarium_user_guide-0.10.2-1.pdfSource snippet
l planetarium. It calculates the positions of the...Read more...
Additional References
-
Source: jpl.nasa.gov
Link: https://www.jpl.nasa.gov/edu/resources/project/find-planets-in-the-sky/Source snippet
Planets in the Sky – Science ProjectFind planets in the night sky and learn about what spacecraft have visited those planets. Then predic...
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Source: cliffsnotes.com
Link: https://www.cliffsnotes.com/study-notes/24665368Source snippet
Explore the Night Sky with Stellarium: A Student's GuideStellarium, a free web-based tool, offers a comprehensive simulation of the night...
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Source: theskylive.com
Link: https://theskylive.com/personalized-star-map -
Source: timeanddate.com
Link: https://www.timeanddate.com/astronomy/night/ -
Source: reddit.com
Link: https://www.reddit.com/r/Astronomy/comments/60x3yg/how_can_i_extract_elevation_and_azimuth_positions/Source snippet
Enter your observing location and it will show you the altitude of an object over the course of the year allowing you...Read more...
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Source: docs.astropy.org
Link: https://docs.astropy.org/en/stable/coordinates/example_gallery_plot_obs_planning.htmlSource snippet
The altitude-azimuth coordinates are then found using astropy.coordinates.EarthLocation and astropy.time.Read more...
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Source: youtube.com
Link: https://www.youtube.com/watch?v=DvWEBrDjyVESource snippet
Altitude, Azimuth, and Zenith in StellariumThe altitude is how far above the horizon you are for your location. The azimuth is what direc...
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Source: youtube.com
Link: https://www.youtube.com/watch?v=qNmlZzlgt5oSource snippet
How to Read a Star ChartIn this video we will review how to read a star chart. This really is a fundamental skill if you are interested i...
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Source: youtube.com
Link: https://www.youtube.com/watch?v=x9cSpKieSkQSource snippet
Using Stellarium to Explore the SkyJoin me in learning how to navigate Stellarium, a free planetarium software that allows users to explo...
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Source: reddit.com
Link: https://www.reddit.com/r/Astronomy/comments/1908ni3/is_there_an_astronomy_app_that_lets_me_define_my/Source snippet
Most of the time, I am taking Astro photos from my deck of my condo. Half the sky is not visible...
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