New Moon 2025-05-27: Why Longitude Matters for Your Charts
“The UT1 time scale is a measure of the rotation angle of the Earth determined with respect to a reference point on the celestial equator. The right ascension of this point is identical to that of the fictitious mean Sun given by Newcomb (see page 73 of the Explanatory Supplement to the Astronomical Ephemeris). Sidereal time is, of course, measured with respect to the vernal equinox. Both time scales are based on the rotation of the Earth, but each is measured with respect to a different reference point … the hour angle of the planet is the difference of between the LAST and the RA. As you suggest the hour angle of the object depends critically on the longitude of the observer ....” (Dr. Dennis D. McCarthy, personal ca. 1980 correspondence).
The “Point located at 50°N, 30°W” should be “… 40°W”, if it really matters to you 🙂.
UT1 (GMT) is “synonymous with mean solar time at the meridian of Greenwich” (see https://www.ucolick.org/~sla/leapsecs/seago.pdf, Intro., paragraph 2, sentence 2). It’s just as longitude dependent as the mean solar time (LMT) of San Diego or any other location. San Diego (117°W) is simply 7h48m EARLIER than Greenwich (0°W). This is how rotational time works.
The question is: How do we calculate or convert the fictitious time on our clocks that is arbitrarily synchronized to a standard meridian based upon the LMT of the Greenwich tabulation of a New Moon? In other words, how do we honor the actual longitude of the physical observer in San Diego rather than his imagined clone on the standard meridian? If you think it can be done, to erect an accurate New Moon chart using standard astrology software, think again.
We've calculated below the local mean time of the New Moon at 117°W (2025-05-26, 7:14:21.046 pm LMT), but the observer's clock is NOT set for San Diego’s LMT; it's set rather for an LMT that's not even his, i.e., the TZ meridian (120°W). It could be viewed rationally as the observer’s Wonderland clone’s LMT, but astrologers should not really engage in such fantasy when calculating charts - New Moon or otherwise! Therefore, we propose instead the actual time on the observer’s synchronized clock is 7:50:21.046 pm PDT at the New Moon, based upon the proper formula that honors longitude (see first example). It’s not an option with our beloved software to calculate this adjusted CT, so you’ll need to find where it’s available (check the end of this article).
The standard chart (calculated and displayed below) for 8:02:21.046 pm PDT appears to be the same as the local mean time chart calculated for 7:14:21.046 pm LMT with an MC = 22° Vir 56'21". It’s only - I cannot emphasize enough - an appearance or illusion, though, not the actual orientation of the observer at 117°W with a clock arbitrarily synchronized to the standard meridian. The proper orientation is rather with a calculated MC = 19° Vir 40'21" at the New Moon. The MC is EARLIER in arc because the observer’s longitude (117°W) is honored. In the standard chart it’s the TZ meridian (120°W) that’s honored instead. Since time is LATER to the east, the observer at 117°W sees the New Moon BEFORE (12 minutes, in fact) the observer at 120°W. The standard formula’s error misaligns your charts - my formula fixes this for true geocentric accuracy!
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Sun-Moon = 6° Gem 05'39.582" (JPL Horizons, accurate to 0.001")
Moon’s apparent NN = 25° Pis 03'24.10" (within 0.01")
Moon’s apparent SN = 26° Vir 20'40.08" (within 0.01")
Moon’s apparent apogee (BML) = 2° Sco 15'09.71" (within 0.01")
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Date: 2025-05-27, 3:02:21.046 UT1
Event: New Moon
1 - Using the proper formula:
UT1 = CT + ΔT_zone + [(λ_obs - λ_std) × 4 / 60]
3:02:21.046 = 19:50:21.046 + 7:00:00 + 00:00:12
Reverse formula:
CT = UT1 - ΔT_zone - [(λ_obs - λ_std) × 4 / 60]
19:50:21.046 = 3:02:21.046 - 7:00:00 - 00:00:12
(or 2025-05-26, 7:50:21.046 pm PDT)
2 - Using the LMT formula:
LMT = UT1 - λ_obs (distance in time from Greenwich)
19:14:21.046 = 3:02:21.046 - 7:48:00
Reverse formula:
UT1 = LMT + λ_obs (distance in time from Greenwich)
3:02:21.046 = 19:14:21.046 + 7:48:00
3 - Using the standard formula:
CT = UT1 – TZ offset
20:02:21.046 = 3:02:21.046 - 7:00:00
Reverse formula:
UT1 = CT + TZ offset
3:02:21.046 = 20:02:21.046 + 7:00:00
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Astrolog Charts using these formulas:
Proposed chart
LMT chart
Standard chart
📣 Take Action: Help Correct the Formula
I’ve launched a public petition to bring this issue to light and push for proper LMT-corrected planetary calculations in all astrology software.
🔗 Sign the Petition on Change.org
This correction doesn’t require topocentric ephemerides, nor does it alter your chart angles. It simply restores accuracy in planetary calculations by honoring the truth of your position on Earth — a truth that’s been neglected for 142 years.
🪐 Astrolog - free astrology software
📨 Want the macro or help integrating it? Just ask — I’m happy to share.
Let’s bring back integrity to astrological timekeeping — one chart at a time.