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Author
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Topic: d-value and d-correction
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Martien
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posted February 13, 2026 03:38 PM
Just finished quiz # 9 and got the results back.
I had several answers wrong, 0020,0023 0024.
These were wrong because I assumed that the +/- for the d value as stated on page 100 bottom right also applied to the d correction , which is not the case . On the both charts they are simply indicated as d but they are different and the rules regarding the d-value do not apply to d- correction as I understand it. I had applied this to HC in box 5 and gave d either a + or a minus depending on the degree going up or down.
This of course affected the range and away or toward and of course the plots. May this help other students.
Martien
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David Burch
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posted February 13, 2026 04:09 PM
This was posted in the Public Discussion, and moved here to look into.
From: Starpath, Seattle, WA
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David Burch
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posted February 13, 2026 04:17 PM
I will leave this to Robert to check details, but I notice that Lesson 9 is on the moon, and a common moon mistake is to confuse the direction that d-value is moving and choosing a sign that way, when in fact we always care what the direction that the actual declination is moving (not the d-value) to determine the sign of d, which is then the sign of the correction.
The declination can be getting bigger with time (+d, +correction) while at the same time the actual d-value is getting smaller, which just means that the declination is getting bigger more slowly as time goes by, but still +d.
Not sure that is the point at hand, but a good point to remember in any event.
From: Starpath, Seattle, WA
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RobertR
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posted February 13, 2026 08:40 PM
I think David is on the money here. I can't be sure without seeing your workforms, but your Zn are consistently correct, and your intercepts were off by amounts entirely consistent with a moon d error.
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Martien
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posted February 23, 2026 12:38 PM
Thank Robert and David,
Sorry about the delay in getting back. I redid the work forms and when I have the correct d +/- then my answers are exactly as per the answers of the quiz.
I will not make that mistake again.
I am enjoying the course very much.
Martien
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