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Almanac and Celestial Navigation Calculator


Sean C

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Hello All,

 

I was advised by ET2SN over at subsim.com to contact Tom Gibson from "Cal Classics" about a spreadsheet I'm working on. It contains a perpetual almanac, sight reduction calculator, position log, great circle route planner (including a database of ~15,500 cities) and a map on which routes and fixes are plotted. I thought it might be handy for simulated celnav.

 

I tried the search feature but could not locate anyone by that name here. Does anyone know how I can get in touch with him? Thanks in advance!

 

 

Also, here is a link to the spreadsheet, if anyone is interested. It's still in beta, but the remaining bugs are very minor (see bottom of instructions tab).

 

 

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Holy bat map, batman. That looks amazing. I have no idea how that works, or what its telling me, and what I should do with it, but its impressive nonetheless.

 

Totally agree! Love it when something I don't understand at all looks incredibly good and I have to learn what it does.

 

Tom will almost certainly see this post.

 

Could you please inform us of any updates or otherwise a link where we can look for them ourselves?

I'm looking to get into SH3 at some point. I assume this may be good for that?

Mark Daniels
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I've grabbed a copy too!:pilot: It meshes with my ideas of science through flight simulation! I was thinking of restarting My Jonesing With Indy pieces from The Old Hangar! :cool: How does a Sea Captain cross the Great Lakes? Lot's of Trigonometry! :pilot:

 

Thanks, Sean!

 

Christopher Tarana

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Hi,

 

Tom Gibson here.

 

This is way over my head, and I only have the free online version of Excel which doesn't display the map.

 

I have posted the link to this message in my forum, so hopefully those more knowledgeable about celestial navigation will take over.

 

Thanks,

Tom Gibson

 

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

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Totally agree! Love it when something I don't understand at all looks incredibly good and I have to learn what it does.

 

Tom will almost certainly see this post.

 

Could you please inform us of any updates or otherwise a link where we can look for them ourselves?

I'm looking to get into SH3 at some point. I assume this may be good for that?

 

I will certainly try to remember to post any updates here. Eventually I want to turn it into a mobile app, but I'm still learning how to do that.

 

If you or anyone here has any questions about celestial navigation, I'd be happy to help. I'm somewhat familiar with the techniques used in the air (more so in the water).

 

Back when I was playing FSX, I had no idea there were celnav mods. I really wish I had. Maybe with the new release it's time to get back in the saddle ... er, cockpit!

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Am not surprised that Chris Tarana posted. See his thread in forum FS2002 "Southern Lights Found in Fs2002" and his post #9 and #11 "Fs2000 Douglas R4D NATS by Bill Rambow, Roy Chaffin, and Jan Visser. It here in the file area!" includes a sextant and screenshot of the cockpit with the sextant. Chris also listed books link in #8 "The Survivors Library website has books about Celestial Navigation also. I grabbed 12 to read! http://www.survivorlibrary.com/". Haven't got into celnav myself but have always been wanting to, given my astronomy interest, and space, and boats, including in-space celnav. Similarly for orbital mechanics. Lovely maths, but all a bit mysterious! :confused:. Amazing stuff Sean C, the hours of work that must have taken to develop. And all in Excel too, wow! Edited by MAD1
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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?

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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.)

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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. :cool: :D

 

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. :p

Edited by BobSeaman
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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. :confused:
  • 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.

 

Btg3DGJh.png

 

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.

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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:

 

N6pK4S9h.png

 

1ojLG07h.png

 

 

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.

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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

 

 

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:

 

 

rx8sgwJh.png

 

 

 

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.

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New version at my website.

 

 

beta v 0.2.7 Bug fixes/changes:

 

  • Fixed a bug causing the intercept "away/toward" cell for sight #10 to remain empty
  • Updated the cities database from ~15,500 cities to Pareto's current [free] offering: 26,570 cities (+ the two suggested cities)

 

 

 

And here's an animation I made showing "Xerxes' Eclipse" on Oct. 2nd, 480 BC:

 

XerxesEclipse2.gif

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My friend recently bought me a rather high-end Celestron telescope for this past XMas. It's computer-controled, but I still want to learn to be able locate and recognize celestial objects from memory - perhaps your spreadsheet may help(?) So thanks for that...
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My friend recently bought me a rather high-end Celestron telescope for this past XMas. It's computer-controled, but I still want to learn to be able locate and recognize celestial objects from memory - perhaps your spreadsheet may help(?) So thanks for that...

 

There are numerous great apps for Android that will help with that: Sextant Stars, Google Sky Map, Nightshift (great app for astronomy) just to name a few. I think you can also get Stellarium on mobile. I don't use Apple products, so I can't advise on that.

 

Stellarium for desktop is an outstanding program, and it's free. My spreadsheet does give some information which would be interesting to amateur astronomers. But I wouldn't recommend it to anyone who isn't somewhat familiar with all of the concepts involved.

 

I have a Travel Scope 80 from Celestron (in addition to all my sextants, transits and other toys). That's what I used to take the 'blue Moon' picture (blue filter also from Celestron) which is the background of the homepage of my website. I want to get an Omni XLT 120 ... but everyone is sold out at the moment. Oh, well ...

 

Cheers!

Sean C

 

kL2wY0I.jpg

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  • 3 weeks later...

New version available at my website.

 

v 0.2.8 - 2021, Feb 28

 

  • Increased the number of decimals of azimuth included in the data series to a ridiculous precision.
  • Fixed a bug causing the spreadsheet to display wildly inaccurate values for the equation of time under certain circumstances.

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