Jan Kampherbeek
If you are interested in astrology, you probably use Facebook. There is a good chance that you have come across an argument by Ron Scott in which he describes an alleged error in the standard calculation of a horoscope. He actively promotes his views, and his posts often generate many responses.
Ron Scott is well informed about the astronomical aspects of astrology, and it is noticeable that people are often receptive to his argument. It would of course be disturbing if his reasoning were correct, but fortunately there is no need to adjust our horoscopes: Scott’s line of reasoning contains a fundamental confusion in the conversion from solar time to UT.
Last month (February 2026) I had an extensive exchange of views with Ron Scott. The discussion was entirely friendly, but we ultimately had to conclude that we could not reach agreement.
In what follows, I will examine Scott’s theory and explain where the error lies.
A practical note: by standard time I mean clock time without taking daylight saving time into account. I use the abbreviation UT to refer to UT, UT1, and TT alike. For the purpose of this article, the distinction does not make a substantive difference; the deviations involved are negligible here.
Ron Scott’s Claim
According to Ron Scott, horoscopes were calculated correctly during the period when LMT (Local Mean Time) was in use. This applies to both planetary positions and houses. Since the introduction of time zones, he argues, the calculation of planetary positions has been incorrect. The calculation of houses, however, remains correct.
Scott appeals to rotational time (UT1, based on the Earth’s rotation) and maintains that the correction for geographic longitude must still be applied separately, even after conversion to zone time.
According to him, we must correct zone time for geographic longitude. He proposes the following formula:
UT = standard time – time zone offset + LMT difference
For the LMT difference, one calculates 4 minutes per degree of longitude, positive for east longitude and negative for west longitude.
The time difference is especially noticeable for the Moon, which can easily change by a quarter of a degree in position. That summarizes Scott’s position.
In support of his theory, he provides extensive numerical examples of the correction for geographic longitude. He submitted these calculations to Seidelmann, a very well-known astronomer, who confirmed that they were correct.
And indeed, those calculations are correct. If you live in Amsterdam, at approximately 5 degrees east longitude, the Sun rises 40 minutes later than in Berlin, which lies at 15 degrees east longitude. For every degree of difference, this amounts to 4 minutes of time.
Another argument he presents is that one must know the geographic coordinates in order to align a telescope. That is also correct. So does Scott have a point? No.
I will explain why the examples he provides are correct but not relevant. And I will show, with a simple calculation, that Scott’s claim cannot be correct.
Geocentric
We must realize several things. This is not about a difference caused by parallax. In these calculations we use geocentric positions. When calculating geocentric positions, we assume the center of the Earth as the reference point. There is only one center of the Earth, and therefore, at a given moment, the positions of celestial bodies are the same for everyone.
This automatically means that at 2:00 a.m. UT (in Greenwich), celestial bodies occupy the same positions as at 3:00 a.m. CET in Berlin and in all other places using CET (zone time). It is the same moment and the same position: the center of the Earth.
According to Ron Scott, the discrepancy arises if I calculate the time for, for example, Amsterdam at 5 degrees east longitude. I would then have to convert those 5 degrees into time and apply a correction of 20 minutes, in addition to the time zone difference.
The numerical examples for geographic longitude differences are correct. But we will see that they are unnecessary because there is a fixed relationship between zone time and UT that allows us to determine UT directly. In essence, the longitude correction is already implicitly incorporated in the conversion to UT.
Zone time = UT + zone offset.
When we convert from zone time back to UT, the zone offset has already been fully accounted for. An additional correction for geographic longitude would apply the same effect twice.
The geocentric position of a celestial body depends solely on the chosen moment in UT, not on the geographic longitude of the observer.
Observations with a Telescope
Why, then, do we need geographic coordinates when using a horoscope with a telescope? Because in that case we must determine the azimuth (compass direction) and altitude (height) of a planet, and these depend on the local horizon. For that purpose, we indeed need the geographic coordinates.
Refutation of Ron Scott’s Theory
I have already mentioned that all positions of celestial bodies are calculated geocentrically. But there are additional arguments.
The timing of eclipses is known with great precision — not only in UT but also in the various time zones. These times correspond to actual observations. If we were to apply Scott’s correction, the Moon could deviate by a quarter of a degree in position — half the apparent diameter of the Moon (and of the Sun). This would be immediately noticeable. Astronomical calculations worldwide agree with observations and use standardized time conversions. The same approach is used in astrological software.
A second argument is equally convincing and has the advantage of providing insight into the mechanism of time zones.
Let us assume a location at 5 degrees east longitude. When LMT is used, the time difference with UT is therefore 20 minutes (5 × 4 minutes). If the local time is 6:00 a.m., UT will be 5:40 a.m.
Now it is decided to switch to CET, the time zone of 15 degrees east longitude. The clock must be advanced by 40 minutes: 10 degrees difference × 4 minutes. From then on, the clock reads 6:40 a.m. The time difference with UT is now 1 hour, and UT therefore equals 6:40 – 1:00 = 5:40. That is exactly the same UT we obtained when starting from a clock set to LMT. There is no difference.
Seven Steps
I have summarized my conclusion in seven steps:
- At a location of 5 degrees east longitude, LMT runs 20 minutes ahead of Greenwich time (UT).
- When the time regulation changes to CET (15 degrees east longitude), we advance the clock by 40 minutes.
- For this location, the difference of 40 minutes between CET and LMT remains constant as long as there are no further changes in time regulation.
- To calculate back from CET to LMT for a location at 5 degrees east longitude, I must subtract 40 minutes from CET.
- A calculation based on LMT presents no problems.
- I can therefore calculate back from CET to LMT and then perform a correct calculation.
- If I subtract 1 hour from CET, I obtain the same UT as in step 6.
When asked, Ron Scott indicated that he agreed with all steps except step 7. His argument: “UT1 at Greenwich is not the same thing as the local rotational condition of an observer displaced in longitude with the time zone.” In effect, he is simply repeating his original claim. He does not explain why, nor does he address the concrete example I provided:
LMT – LMT offset = UT, numerically: 6:00 – 0:20 = 5:40
Zone time – LMT = LMT correction, numerically: 6:40 – 6:00 = 0:40
Zone offset = LMT offset + LMT correction = 0:20 + 0:40 = 1:00
This calculation is internally consistent. In Scott’s view, we would need to add the LMT offset once again to the zone offset. That would mean applying the same correction twice.
I believe the examples speak for themselves. Based on the reasoning above, there is no reason to change the current calculation method.
The proposed modification is incorrect. Is it wise to devote attention to it? I think it is unavoidable. On Facebook there are many discussions about Ron Scott’s theory, sometimes with hundreds of comments. This debate shows how important it is for astrologers to be familiar with the astronomical foundations of astrology. A reliable approach to astrology requires that we base ourselves on the facts.
I would like to add that my discussion with Ron Scott was conducted in a courteous and pleasant manner. I genuinely believe that he is convinced he is right. However, the computational consequences of his proposal are not consistent with the time conversion as applied in astronomy.
References
Meeus, Jean: Astronomical Algorithms. Richmond, 1998. This publication provides a good overview of the various time scales.
Scott, Ron: Why the LMT Variation Matters in Chart Calculation. Online: https://rscott51.substack.com/p/why-the-lmt-variation-matters-in (visited 19 Feb. 2026).
Published: March 4, 2026
A Dutch version of this article previously appeared in the ‘NVWOA Nieuwsbrief’.