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Thread: Almanac and Celestial Navigation Calculator

  1. #11
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    Mar 2005
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    Australia
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    Quote Originally Posted by Sean C View Post
    Please be advised: I have recently learned that opening my spreadsheet in LibreOffice or any program other than modern versions of MS Excel may result in loss of functionality or errors in output data.
    That’s my problem. I don’t have MS office yet.
    So I’m assuming this is used with the sextant thingie?

  2. #12
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    Jan 2021
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    Norfolk, VA, USA
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    Arrow Update!

    Quote Originally Posted by JSMR View Post
    That’s my problem. I don’t have MS office yet.
    So I’m assuming this is used with the sextant thingie?
    Some beta testers have reported that the almanac works in LibreOffice. Others have had problems. IIRC, the buttons disappear regardless - but it should still basically work. I may try and "port it over" in the future. No promises.

    And yes: it is intended for use with a sextant/octant/astrolabe/theodolite/etc. Anything that can measure the apparent altitude of a celestial body above the horizon. It would also be somewhat useful for amateur astronomy with a telescope.

    By the way, celestial navigation is really not that hard. You must keep in mind that the system was designed for the average sailor or pilot to be able to understand and execute even when under some stress. I never went to college, and I barely made it through algebra and geometry, let alone spherical trigonometry.

    But that's the point: you don't have to understand trig at all to do celnav. Because people like me have done it for you. And if I can do it, anyone can! Even with traditional paper methods, the only math skills usually required are addition and subtraction. The rest is just filling in blanks and perfecting your sextant technique.

    And as always: if anyone has any questions, just ask!

    Also, I have updated my spreadsheet.

    Bug fixes/changes:

    • There was a bug causing some leap year dates to be calculated incorrectly. I fixed it ... I think.
    • Updated the delta-T values and extended the table into the past just a little. o.O
    • The notes on the Almanac tab did not reflect the changes. I polished them until they did.


    Should be even more accurate now. (Still only guaranteed to work on Excel, sorry.)

    Link to the updated version.


    (Links to old versions will eventually be broken.)

  3. #13

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    Quote Originally Posted by Sean C View Post
    Hello All,

    I was advised by ET2SN over at subsim.com to contact Tom Gibson
    Be careful, that ET2SN guy can be a little flakey.

    Some people claim that he spent too much time brushing his teeth at Test Depth. Others will say that a shipyard did him in. But those in the know might tell you it was a dual channel INS that really didn't want to be a dual channel INS that did him in.

    Just make sure you don't have any cold beer in your fridge if he comes over.
    Last edited by BobSeaman; 01-09-2021 at 09:00 PM.

  4. #14
    Join Date
    Jan 2021
    Location
    Norfolk, VA, USA
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    15

    Arrow Update!

    Bug fixes/changes:

    • Fixed the bug preventing the sight reduction cells from clearing correctly ... I think.
    • Delta-T values are now interpolated for dates between table entries. This will have the most noticeable effect on really old dates which cannot be completely trusted anyway.
    • Added a note about compatibility issues. We're just not right for each other. (LibreOffice, not you - you're cool.)
    • Discovered the "Application.ScreenUpdating" VBA object. The spreadsheet generally runs more smoothly after a liberal application to the macros (as you do).
    • Added a nifty sky chart showing the positions of all visible traditional navigational bodies for the currently selected time and location which isn't quite what I intended, but looks pretty cool nonetheless.


    Link to new version.



    I still want to add Sunrise/set/twilight times. And maybe even some other calculators such as "Time Sights" and "Lunars". We'll see ...


    Enjoy!


    Sean C.

  5. #15
    Join Date
    Jan 2021
    Location
    Norfolk, VA, USA
    Posts
    15

    Arrow Update!

    Bug fixes/changes:

    • Fixed a long forgotten bug causing DRs to be calculated incorrectly when crossing the IDL.
    • Fixed the bug causing the "Send to Log" button to overwrite manual entries.
    • Added a "Data Series" tab which calculates data for a specified period and interval.
    • Created a new bug by doing the above. (See "Instructions" tab.)
    • Added a bar below the sky chart which indicates day/twilights/night.
    • Added notes about stellar positions/magnitudes on the "Instructions" tab.
    • Updated my contact email address. Please do not send mail to the previously listed one. Thank you.



    Link to the zipped spreadsheet.

    Link to the unzipped spreadsheet.

    All older links will now be broken.

    Current list of features:

    Perpetual almanac which lists basic data necessary for celestial navigation
    Sky chart showing traditional nav bodies above the horizon
    Data series calculator for comparison/analysis
    DR and sight reduction calculator
    Position log
    Great circle route calculator including internal database of ~15,500 cities worldwide
    Internal delta-T values for dates between 500 BC and AD 2030
    Custom delta-T value fields for dates outside the above range - or whenever
    Only 2MB


    The new data series calculator can be used to make charts like the following for data comparison or analysis:






    Some stats:

    Total Sheets: 18
    Cells with data: 180,868
    Tables: 4
    Formulas: 8,373
    Charts: 2
    Macros: 26
    Days I've been working on it so far: 237


    I will probably only post new versions at SubSim and NavList from now on ... unless someone really wants me to keep posting them here. You should always be able to find the latest version at one of the above sites.

  6. #16
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    Jan 2021
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    Norfolk, VA, USA
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    15

    Red face Oops.

    Just found a new bug: the data series calculator gives incorrect distances for stars. That will be fixed in the next version.

  7. #17
    Join Date
    Mar 2005
    Location
    Boca Raton, Florida, USA.
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    @ Sean C

    Hi,

    I tried your LINK

    " here is a link to the spreadsheet"

    and it does NOT work.

    How can I download the program, PLEASE ?!
    Sincerely

    G. Kirschstein

  8. #18

    Default

    The working links are in post #15 - all previous links are broken, as he warns in his posts.
    Tom Gibson

    CalClassic Propliner Page: http://www.calclassic.com

  9. #19
    Join Date
    Jan 2021
    Location
    Norfolk, VA, USA
    Posts
    15

    Arrow Update!

    Quote Originally Posted by GKKnupper View Post
    @ Sean C

    Hi,

    I tried your LINK

    " here is a link to the spreadsheet"

    and it does NOT work.

    How can I download the program, PLEASE ?!
    Sincerely

    G. Kirschstein

    Here is a new version:

    Bug fixes/changes:

    • Fixed a bug causing the data series tab to display incorrect distances to some stars.
    • By request: Added Hiva Oa and Nuku Hiva, Fr. Polynesia to the city database.
    • Added unit indicators to the data series table headers.
    • Clarified the note about stellar magnitudes.
    • Added some credits to the "Instructions" tab.


    Zipped spreadsheet.

    Unzipped spreadsheet.


    And here is another example of the type of things you can do with the data series calculator:






    This chart of the recent conjunction of Jupiter and Saturn was made using the formula:

    acos(sin(dec.1) · sin(dec.2) + cos(dec.1) · cos(dec.2) · cos(GHA1 - GHA2 ))

    Hint: To convert a Julian Date to an Excel date, simply subtract 2415018.5 from the JD and format it as a date and/or time. Note, however, that Excel itself does not recognize dates before January 1st, 1900.

  10. #20
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    Jan 2021
    Location
    Norfolk, VA, USA
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    15

    Default

    New version is available at my new website:


    https://www.cooknavigation.com

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