How to Use an Almanac To Explore the Night Sky
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I see in the October 1793 that the Sun Fast column reflects the Equation of Time: it goes from +11 minutes on October 1 to +16 minutes on October 31. But the August 2017 Sun Fast is not the equation of time - it goes from +9 minutes on August 1 to +16 minutes on August 31. According to the Equation of time, that +9 on August 1 should be -6 minutes, and the +16 on August 31 should be 0 minutes.
Why is Sun Fast not the Equation of Time? Is there some additional factor I need to subtract from the OFA's Sun Fast to get the Equation of Time? It looks like Sun Fast is ahead by 16 minutes.
There are at least 3 corrections that are needed to convert between watch time and sundial time: equation of time, longitude correction, and daylight saving time (if applicable). Latitude also plays a part in positioning the sundial.
From what I understand, it looks like the 1793 Old Farmer’s Almanac edition used the longitude for the central meridian of the Eastern time zone, 75 degrees west. However, the 2017 Almanac (and our current editions) calculate based on Boston, which is east of the central meridian, at about 71 degrees 3 minutes west. If I’ve done the calculations correctly, that is a +15.8 minute adjustment (since Boston is east of the central meridian, add the minutes). If this is right, then the August data published in the 2017 Almanac is correct, once the correction for longitude is added to the equation of time.
August 1, 2017:
-6 minutes (equation of time, sun slow) + 15.8 minutes (longitude correction) = 9.8 minutes (or roughly 9, as in the Almanac)
August 31, 2017:
0 minutes (equation of time) + 15.8 minutes (longitude correction) = 15.8 minutes (or roughly 16, as in the Almanac)
Hope this helps!
In the 1793 version of the almanac there is a column that reads "Place". Then, vertically it reads belly, reigns, thigh, heart, knee....etc. What does this mean?
This column listed the Moon’s astrological place. In astrology, each zodiac sign is associated with a part of the body (Man of Signs). For example, “feet” refers to Pisces, and “heart” refers to Leo. You can find this information in the 2018 Almanac on the left-hand calendar pages under the column furthest to the right with a crescent moon symbol and “ASTROL. PLACE” heading. A full chart is also included in the back, on page 239. Please note that this is different from the Moon’s astronomical place (also a column on the left-hand pages, abbreviated as “ASTRON. PLACE”) which is the Moon’s place in the constellations in the sky at midnight—useful for sky-watchers. For more information about the Man of Signs, see: