Definitions of Various Terms Under Perpetual Calendar, Equation of Time, Mean Time: Brocot

Discussion in 'General Clock Discussions' started by prideofmatchingham, Oct 13, 2019.

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  1. prideofmatchingham

    prideofmatchingham Registered User
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    Would like the forum to enlighten me on various aspects of a perpetual calendar clock along with meaning and valculation of equation of time, meaning and calculation of Mean time.

    I also request the forum to enlighten me on what is meant by NM, FQ, FM, LQ, NM on this clock and calculation.

    I know it might be a tall order to satisfy these queries on a forum but one can start from basics!

    Also, this is a similar clock that sold in Christies. It can be seen here

    A French large gilt-brass striking eight day four-glass mantel clock with perpetual calendar and moonphase , ACHILLE BROCOT, PARIS. CIRCA 1880

    What do they mean by a 'four year indicator' in their description? IMG_20191012_160757.jpg
     
  2. novicetimekeeper

    novicetimekeeper Registered User

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    Greenwich Mean Time - Wikipedia


    The equation of time is the correction from solar. Using it you can set your pocket watch from a sun dial.

    I don't see the letters you speak of, do you mean the symbols of the Zodiac?
     
  3. novicetimekeeper

    novicetimekeeper Registered User

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    The four year cycle refers to leap years.
     
  4. jmclaugh

    jmclaugh Registered User

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    NM, FQ, FM, LQ I think refers to phases of the moon, so new moon, first quarter, full moon and last quarter.
     
  5. prideofmatchingham

    prideofmatchingham Registered User
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    I think i rather splurged!

    Here are those moonphase notations which jmclaugh seems tobhave got correctly.

    Now unlessninu derstand each tjing, how do I set my time as per equation of time and mean time at noon?

    Screenshot_20191013-195047~2.jpg Screenshot_20191013-195047~2.jpg
     
  6. novicetimekeeper

    novicetimekeeper Registered User

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    This is not quite as complicated as yours but similar. Gaius is on the NAWCC facebook group.

     
  7. D.th.munroe

    D.th.munroe Registered User

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    I don't like doing this, but your clock doesn't have an equation of time indicator, that hand is just the age of the moon (which seems redundant with the moon underneath it) also it appears the hand is a few days ahead of the moon.
    Dan
     
  8. prideofmatchingham

    prideofmatchingham Registered User
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    Hi Dan

    Thanks for your comment. Wonder why dont you like 'doing this', afterall you are educating me by showing what I am mistaking and where I am erring.

    Request you to link some other clock with equation of time and make us understand this. If you try with mathematical equatons, i would be ok.

    Also, the clock was not working for 2 days during its transit period. Would that have affected the anomaly you pointed out?

    How does this hand work so that we know how to adjust after service.

    Thank you for your reply and glad to have made your acquaintance here.

    PrideOfMatchingam
     
  9. novicetimekeeper

    novicetimekeeper Registered User

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    Yes that pointer goes to 29.5 so that is the lunar date. It obviously has a snap back action though when it gets to 29.5.

    You need to look up when the full moon is and then that gives you a lunar date of 15. Work out how many days away that is from the current calendar date and that gives you the offset for the date.

    It is full moon tonight so today is 15th lunar day.
     
  10. prideofmatchingham

    prideofmatchingham Registered User
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    Your reply woke me up (its 2305 hrs here) and made me run to the drawing room to check lunar day as today is full moon and 15th day, as you pointed out. Here is the picture

    IMG_20191013_230002.jpg

    Now what else?

    Thanks
     
  11. novicetimekeeper

    novicetimekeeper Registered User

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    It says it is sunday 12 Oct so isn't the calendar a day out? (Although the day and date may click through at different times, so it may be something to do with that)
     
  12. James McDermaid

    James McDermaid Registered User
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    Perpetual Calendar Clocks were popular starting in the late 1800's around 1875 (check the history for accuracy here). A perpetual Calendar clock automatically indicates the Date, Day, and Month on a calendar dial and it automatically shows 31, 30, 28, and 29 day months without human intervention (keep the clock running and wound).

    Sun Dials indicate time by the suns shadow which changes position in the sky throughout the year. The equation of time which was often on the sun dial allowed the observer to correct the indication provided they knew the date and month. Our mechanical clocks and watches indicate Mean Time which is an average of Sun time, Solar time, or Sidereal Time.

    I hope I am correct here. Jim
     
  13. prideofmatchingham

    prideofmatchingham Registered User
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    Your reply woke me up (its 2305 hrs here) and made me run to the drawing room to check lunar day as today is full moon and 15th day, as you pointed out. Here is the picture

    View attachment 552161

    Now what else?

    Thanks
     
  14. prideofmatchingham

    prideofmatchingham Registered User
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    I think date will change 12 hours later!! What happened is whenni got these here, it was in transit for a day and half. When i set the time in my home in second half of 11th, i didnt go second round (1-12 and then 12 to 3PM). Hence date may change at 3 PM i think. (I will keep an eye on it).

    But if that were the case, would meantime hand also be a bit before 15? Or the two functions are independent in the movement?
     

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