Within Halt Night
Were the Radiation Readings Actually Unusual?
Halt's Geiger counter readings became famous evidence, but critics argue they were low and inconsistent background values.
On this page
- What Halt's memo reported
- What the tape records in the field
- Why sceptics dispute the anomaly
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Introduction
The radiation measurements taken during Lieutenant Colonel Charles Halt’s night-time investigation are often presented as one of the few pieces of physical evidence from the Rendlesham Forest incident. Yet they are also among the most disputed. Supporters of the case point to recorded instrument readings in and around the three small ground depressions found at the alleged landing site. Critics counter that the readings were low, only marginally above nearby measurements, and entirely consistent with ordinary environmental background radiation. The debate is important because it concerns one of the rare occasions in the Rendlesham story when investigators used an instrument rather than relying solely on witness observations.
What Halt’s Memo Reported
Halt’s memorandum of 13 January 1981 gave the most widely cited summary of the radiation findings. According to the memo, investigators returned to the area where an unusual object had allegedly been seen and examined three shallow depressions arranged in a triangular pattern. The document states that beta/gamma radiation readings of 0.1 milliroentgens were recorded, with peak readings in the depressions and near the centre of the triangle. It also reported readings of roughly 0.05–0.07 milliroentgens on the side of a nearby tree facing the depressions. [Ian Ridpath+2markfoster.net]ianridpath.comIan RidpathAppendix – Col Halt's memo to the MoDThis is the text of the single-page memo written by Lt Col Halt to the UK's Ministry of D…
Read in isolation, the memo can create the impression that investigators discovered a measurable anomaly associated with the alleged landing site. Because the document was written on official US Air Force stationery by the deputy base commander, it became one of the strongest documentary pillars of the Rendlesham case. [Ian Ridpath]ianridpath.comIan RidpathAppendix – Col Halt's memo to the MoDThis is the text of the single-page memo written by Lt Col Halt to the UK's Ministry of D…
The difficulty is that the memo provides only selected values and little context about what the survey instrument normally registered in the local environment. That missing context became central to later sceptical analysis. [Ian Ridpath]ianridpath.comIn short, there was no unusual radiation at the site.Read more…
What the Tape Records in the Field
The audio recording made by Halt during the investigation paints a more nuanced picture than the later memo. The team carried an AN/PDR-27 military radiation survey meter and moved around the depressions comparing readings from different locations. Recorded comments indicate that the instrument was producing only minor clicks at first and that investigators were trying to determine whether any differences were meaningful. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
Reconstructions based on the tape indicate readings of about 0.07 milliroentgens per hour at the depressions and approximately 0.03–0.04 milliroentgens per hour in nearby areas. Investigators also reportedly found a comparable increase at another location some distance away from the alleged landing site. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
These details matter because they shift the question from “Was radiation detected?” to “Was the detected level unusual?” No one disputes that the meter registered radiation. The dispute concerns whether the measured differences represented anything beyond ordinary fluctuations in background levels. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
The Instrument Itself
The AN/PDR-27 was a standard military radiation survey meter designed primarily for monitoring radiation hazards. It was not a specialised forensic instrument intended to identify subtle environmental anomalies decades after an event. Critics argue that small variations at the scale recorded during the investigation fall within the sort of differences that can occur naturally due to soil composition, moisture, geology, or instrument response. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
This does not mean the instrument malfunctioned. Rather, it means that interpreting a slight increase requires knowledge of the expected local background and the meter’s precision—information that was not fully documented in the surviving records. [Ian Ridpath]ianridpath.comIan Ridpath Rendlesham Forest UFOIan RidpathRendlesham Forest UFO - the radiation readings 2This is Nick Pope's handwritten memo concerning the radiation readings from th…
Why Sceptics Dispute the Anomaly
The sceptical case rests on three closely related arguments.
First, the reported values were low. Researchers who examined the figures noted that readings in the range recorded by Halt’s team are consistent with ordinary background radiation from natural sources such as cosmic rays and radioactive materials naturally present in soil and rock. Consultations with radiation experts cited by investigator Ian Ridpath concluded that the measurements were not extraordinary. [Ian Ridpath]ianridpath.comIn short, there was no unusual radiation at the site.Read more…
Second, the differences between locations were small. A reading of approximately 0.07 milliroentgens per hour compared with nearby readings around 0.03–0.04 milliroentgens per hour represents only a modest variation. Critics argue that if a highly unusual radiation source had recently occupied the site, one might expect a clearer and more dramatic contrast. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
Third, similar elevated readings reportedly appeared elsewhere. Accounts of the survey note that comparable spikes were found away from the depressions themselves. If correct, that weakens the claim that the measurements uniquely marked the alleged landing area. [Wikipedia]WikipediaRendlesham Forest incidentRendlesham Forest incident
For sceptics, the radiation evidence therefore does not independently support the idea that an extraordinary craft landed in the forest. Instead, they view it as a normal environmental reading that later acquired greater significance through repetition and retelling. [Ian Ridpath]ianridpath.comIn short, there was no unusual radiation at the site.Read more…
Why the Readings Remain Part of the Debate
Supporters of the Rendlesham case generally do not rely on the radiation measurements alone. Rather, they argue that the readings gain significance when combined with the reported ground depressions, alleged tree damage, multiple military witnesses, and Halt’s contemporaneous audio recording. In that interpretation, even a modest radiation increase may be seen as one element of a larger pattern. [Prometheus Unbound]wordpress.com3. Later in the night a red sun-like light was …Read morePrometheus UnboundThe Rendlesham Forest UFO Incident: The Testimony of Sgt …20 Aug 2009 — A nearby tree had moderate (0.05–0.07) readin…
Critics respond that physical evidence should stand on its own merits. If the radiation values are ordinary background measurements, then they cannot reasonably be treated as scientific confirmation of an unusual object. From this perspective, the readings are noteworthy mainly because they illustrate how the same data can be interpreted very differently depending on the wider narrative attached to them. [Ian Ridpath+2The Black Vault Documents]ianridpath.comIn short, there was no unusual radiation at the site.Read more…
The Core Question
The radiation dispute ultimately turns on a narrow technical issue rather than a dramatic mystery. Halt’s team did record measurable radiation at the alleged landing site. The unresolved question is whether those measurements represented anything abnormal.
The surviving evidence strongly supports the conclusion that radiation was detected. It does not, however, establish a consensus that the detected levels were unusual. The figures cited in the tape and later analyses fall within ranges that many radiation specialists and sceptical investigators regard as normal background variation. As a result, the radiation readings remain one of the most frequently cited pieces of physical evidence from the second-night investigation while simultaneously being one of the least persuasive to critics. [Wikipedia+2Ian Ridpath]WikipediaRendlesham Forest incidentRendlesham Forest incident
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Further Reading
Books and field guides related to Were the Radiation Readings Actually Unusual?. Use these as the next step if you want deeper reading beyond the article.
Encounter in Rendlesham Forest
Covers the radiation measurements and debates surrounding them.
The UFO Experience
Provides context for evaluating instrument readings and reported anomalies.
UFOs and Government
Discusses official investigations and physical-evidence claims in UFO cases.
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Endnotes
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Source: markfoster.net
Link: https://www.markfoster.net/struc/Rendlesham_Forest_MoD.pdfSource snippet
Report of Sighting, Rendlesham Forest.1 Nov 2000 — The next day, [three depressions]({{ 'three-marks/' | relative_url }}) 1 1/2" deep and 7" in diameter were found where the ob...
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Source: Wikipedia
Title: Rendlesham Forest incident
Link: https://en.wikipedia.org/wiki/Rendlesham_Forest_incident -
Source: ianridpath.com
Link: https://www.ianridpath.com/ufo/appendix.htmlSource snippet
Ian RidpathAppendix – Col Halt's memo to the MoDThis is the text of the single-page memo written by Lt Col Halt to the UK's Ministry of D...
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Source: santitafarella.wordpress.com
Link: https://santitafarella.wordpress.com/2009/08/20/the-rendlesham-forest-ufo-incident-the-testimony-of-sgt-james-[pennistonSource snippet
Prometheus UnboundThe Rendlesham Forest UFO Incident: The Testimony of Sgt...20 Aug 2009 — A nearby tree had moderate (0.05–0.07) readin...
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Source: ianridpath.com
Link: https://www.ianridpath.com/ufo/rendlesham1b.htmlSource snippet
In short, there was no unusual radiation at the site.Read more...
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Source: ianridpath.com
Title: Ian Ridpath Rendlesham Forest UFO
Link: https://www.ianridpath.com/ufo/rendlesham4a.htmlSource snippet
Ian RidpathRendlesham Forest UFO - the radiation readings 2This is Nick Pope's handwritten memo concerning the radiation readings from th...
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Source: documents.theblackvault.com
Link: https://documents.theblackvault.com/documents/ufos/UK/defe-24-2005-1.pdf -
Source: documents.theblackvault.com
Link: https://documents.theblackvault.com/documents/ufos/UK/defe-24-2094-1.pdfSource snippet
readings reponed by Lieutenant Colonel Halt. From a Defence perspective some 161 years after the alleged events. there is no requirement...
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Source: science.howstuffworks.com
Title: rendlesham forest incident
Link: https://science.howstuffworks.com/space/aliens-ufos/rendlesham-forest-incident.htmSource snippet
Feb 27, 2024 — Col. Charles Halt, led a larger party into Rendlesham. There, Halt measured abnormal amounts of radiation at the original...
Additional References
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Source: medium.com
Link: https://medium.com/illumination/the-day-the-ufo-landed-on-a-military-base-and-they-kept-it-quiet-e1aa242c827eSource snippet
The Day the UFO Landed on a Military BaseThe radiation levels recorded at the site. The formal memo written by a high-ranking officer. So...
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Source: theguardian.com
Link: https://www.theguardian.com/world/2026/apr/30/the-rendlesham-forest-mystery-its-the-perfect-storm-of-a-ufo-caseSource snippet
The most notable encounter involved U.S. Air Force personnel Jim Penniston, John Burroughs, and Charles Halt, who reported strange lights...
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Source: facebook.com
Title: in december 1980 us air force personnel saw strange lights in rendlesham forest
Link: https://www.facebook.com/mrballen/posts/in-december-1980-us-air-force-personnel-saw-strange-lights-in-rendlesham-forest-/908029534929214/Source snippet
Air Force personnel saw strange...Radiation readings taken at the original landing site showed levels higher than background radiation...
Published: december 1980
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Source: dokumen.pub
Link: https://dokumen.pub/conspiracy-of-silence-and-the-ufo-problem-1stnbsped.htmlSource snippet
ights into what happened to Betty Cash, Vickiee Landrum and Colby on...Read more...
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Source: hangar1publishing.com
Link: https://hangar1publishing.com/blogs/ufos-uaps-and-aliens/rendlesham-forest-incident?srsltid=AfmBOorGBIohXvjxGUjAJ8pg3YiblGq0ouxZE-Npl5E-okHxDvzgNK6jSource snippet
Rendlesham Forest Incident: Britain's RoswellUpon reaching the alleged landing site from the [first night]({{ 'first-night/' | relative_url }}), Halt's team took radiation read...
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Source: reddit.com
Link: https://www.reddit.com/r/publicdomain/comments/1ona0fm/unexplained_lights_aka_the_halt_memo_by_charles/Source snippet
in the forest. Full Audio Recording from Colonel Charles Halt made...
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Source: facebook.com
Link: https://www.facebook.com/HISTORY/posts/retired-col-charles-halt-recounts-the-unexplained-lights-he-saw-in-rendlesham-fo/10156037522506184/Source snippet
aimed at the military base. An official memorandum went to the...
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Source: iheart.com
Title: the halt memo one page that 331910094
Link: https://www.iheart.com/podcast/1333-rendlesham-forest-1980-th-331910086/episode/the-halt-memo-one-page-that-331910094/Source snippet
The Halt Memo: One Page That Changed Everything27 Apr 2026 — It confirms every major element of the incidents, the depression in the soil...
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Source: pocketmags.com
Title: rendlesham forest 33 years oncolonel charles halt usaf (ret) speaks out
Link: https://pocketmags.com/magazine-articles/rendlesham-forest-33-years-oncolonel-charles-halt-usaf-%28ret%29-speaks-out?srsltid=AfmBOorvk5WmaBeC5BZkWodfMG26Uh5iXffHI9PgInaADZkX16jbbxzlSource snippet
There were marks on the trees facing the indentations and branches were...Read more...
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Source: commons.wikimedia.org
Title: Commons File:Halt Memorandum.jpg
Link: https://commons.wikimedia.org/wiki/File%3AHalt_Memorandum.jpgSource snippet
Wikimedia CommonsFile:Halt Memorandum.jpg - Wikimedia CommonsEnglish: Memorandum by Lieutenant Colonel Charles Halt to the British Minist...
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