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SeanPatrick 23-01-2021 23:41

I'm humbled.
Wow! What a great response! I would have been happy if just one person thought my spreadsheet might be useful. I cannot tell you all how happy it makes me to hear that multiple people are now thinking about dusting off their sextants or learning celestial for the first time! And thank you, everyone, for the kind words.

I just got settled in after a long day, but I'm going to respond to each and every question asked. But first: I'm going to fix that bug I found this morning and add those two cities that Apollo366 asked for. (Both should be easy fixes, fortunately.)

Be back soon ...


SeanPatrick 24-01-2021 01:59

Okay, here is the next version:

Zipped spreadsheet.

Unzipped spreadsheet.

(Mods: would it be possible to update the links in the first post, please? Thank you!)

Bug fixes/changes:

  • Fixed a bug causing the "Data Series" tab to display incorrect distances to some stars. (The workbook doesn't even calculate stellar distances.)
  • 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.

Also, I apologize for the trouble some people have had downloading the workbook. I need to find a better [easier] file sharing service. (Any suggestions?) But, as Kamen said: you may need to click the little arrow at the top right of the screen before the download button becomes visible.

Don't feel bad. I even had trouble figuring it out myself. :facepalm:

Q&A to follow shortly ...

SeanPatrick 24-01-2021 04:13

Q&A Time!
I'd like to start with one question in particular, because I think it is the best question I've gotten so far:


Originally Posted by gerson (Post 3326515)
Wonderful but i use:
and there is a lot of almanacs in the market
why your is better?

My answer is: It isn't. Stellarium is an awesome program and I use it all the time. But AFAIK, Stellarium won't do all the things that my spreadsheet does. Nor will my sheet do what Stellarium does. And you are correct that there are a lot of other almanac programs out there. Some of my favorites are: Teacup Navigation by Roger Farley, AstroNav by NavSoft, Navigational Algorithms by Andres Ruiz González (also on mobile) and MICA by the USNO. Some of those are free, some aren't - but I think they are all well worth the price. So ... why mine?

Maybe a little background would help: My absolute favorite almanac program of all time was ICE - the USNO's Interactive Computer Ephemeris. It ran on DOS and was geared mainly toward navigation, with (IIRC) a little extra astronomy stuff. Well, ICE has long since been replaced by MICA and another program (the name of which escapes me at the moment). Now, I can still run ICE today using DOSBOX or similar, but the delta-T values are so far off that it is just not worth it. Hence the inclusion of a user-editable delta-T tab in my spreadsheet.

My next favorite program is MICA, and it still outputs accurate data today. Unfortunately, the one and only vendor of the program (Willmann Bell) has closed. Hopefully a new vendor will be found soon. Besides that, MICA is sort of the opposite of ICE in that it seems mainly geared toward general astronomy, with navigation taking a back seat. It is incredibly powerful, but not my ideal. And all of the other programs are great, too. But I always think I would like to see things done a little differently. So ... I made my own. Eventually I plan to turn it into an app (I'm learning how to do that now) and maybe a PC program too ... a command line program. :)

Bottom line is: there is absolutely no reason not to use Stellarium (unless it really does have errors in some proper motions as has been discussed on NavList) or any other program or method - as long as you like it. There is also no reason you cannot use them all. Except the USNO website (another great resource) which is down for an indeterminate amount of time. :(

Tell you what: if you are not completely satisfied with my spreadsheet, I will give you a full refund! ;) Seriously, though: thank you for giving me the chance to explain a little about my motivation.



Originally Posted by double u (Post 3326408)
I always found the idea of combining a traditional, "handicraft"-type of skill like celestial with computers highly hilarious.

I do too. It always feels like cheating to me (like grantmc said) in this context ... or almost even (dare I say) pointless. (And I'm not being flippant.) The idea being that you're planning to use celestial when all the electronics don't work. I have shelves upon shelves of navigation books. I even have a 1781 printing of the Tables Requisite. However, sometimes I want to reduce a round of sights quickly, or maybe go back over a bunch of old sights, or even just use the incredible computing power available to play around and see what time the Sun set in Timbuktu ... in 1502.

But there's also another thing to consider: celestial as a backup. Frank Reed has made an app which instantly allows you to check if your GPS is inaccurate for whatever reason. All you need is a sextant, his app and maybe a dodgy GPS signal. Or you could just use it to practice your sextant technique, it's great for that, too. That's another thing: tools like this are great for learning and checking to see if you're doing it right.

Anyway, point is: there are some good reasons for it. But I still haul out the tables from time to time. ;)


Originally Posted by Smokeys Kitchen (Post 3326486)
Wondering if the updated version(s) will be on the same link? Haven't looked at the link yet - but will there be a note regarding the versions?

Unfortunately no, not for the time being. I apologize. I will work on a better delivery method. I do plan on setting up a web page soon with other resources.


Originally Posted by Russ (Post 3326535)
Great Spread Sheets but how do I download to actually USE it.
Sorry not enough of a computer geek
Russ [et al.]

Apologies. Please see my previous post.


Originally Posted by SaltyMetals (Post 3326596)
From the little that i remember from 30 years ago i notice one of your screenshots is for details of the moon but surely it should be "lower limb" ?

I'm not sure where you saw that, but it is entirely possible. There are in fact times when you need to use the upper limb. Certain arrangements of the celestial bodies, cloud covering the lower limb, doing a backsight, etc. These conditions are admittedly the exception, though.


Originally Posted by StoneCrab (Post 3326764)
Is it even possible anymore to purchase a current Nautical Almanac?

It may not be in the near future, who knows? With the USNO site down and Willmann Bell closing their doors, I wonder. But, as Apollo366 mentioned: there are some great long-term almanacs available. I highly recommend this one:

Long Term Almanac 2000-2050: For the Sun and Selected Stars with Concise Sight Reduction Tables, 2nd Edition


Originally Posted by Apollo366 (Post 3326776)
Hi Sean, I just tried using the Great Circle calculator and you don't have Hiva Oa or Nuka Hiva, Fr Polynesia in the data base.
As these are the two most common destinations leaving Balboa, Panama for the So Pacific, can you include them or show me how to add them please?

I haven't looked, but are all the other common Coconut Milk Run destinations included?

Many thanks,

Done. The data was copied almost verbatim from Pareto, so I don't know what all cities are in there. I just checked a few to see if it all worked. It's trivial (for me) to add new ones. The sheet is [supposed to be] hidden and locked because I didn't really anticipate adding to it much. Maybe I'll unlock and unhide it in a future version, IDK.


Originally Posted by hzcruiser (Post 3326865)
I tried the beta 0.24 it with "Numbers" and "Open Office" on a Mac M1. Numbers could open it and seems to work, OO crashes on every attempt.

Yeah ............ I'm not too happy about the fact that LibreOffice and Numbers can simply bypass the password protection I carefully put in place to keep anyone from copying months of my hard work. But the blame for that rests squarely on Microsoft's shoulders and no one else's.

Thank you for testing it, though!


Originally Posted by Invictus69 (Post 3326898)
Until some years ago I have been occasionally using Starpath Perpetual Almanac (, mostly for double checking the GPS chartplotter

Curious if someone can share experiences or comparison between the two.

I haven't tried Starpath's so I don't know. But I do know they are a great school, so I imagine whatever they are using is at least as good as my spreadsheet.

Anyway, I hope that answered some questions. If I missed any, please let me know. I will try to answer as many future questions as I can, too.



SeanPatrick 24-01-2021 05:20

By the way, it just struck me that it might not necessarily be immediately obvious that some of the cells that are automatically filled can also be filled manually. This includes:

  • The DR, date and the dip and IC on the "Sight Reduction" tab, so you can use your own DR calculation or sights from different dates.
  • The "Log", so you can add other types of fixes/entries.
  • The departure and destination on the "Course" tab, so you can plot a course to and from any two points on Earth, not just the cities in the database.

Also, a tip for Excel in general: If you want to change the value in a cell, but don't want to select another cell (like [Enter] and [Tab] will do), you can hit [Ctrl]+[Enter]. This will change the data in the cell, but the same cell will remain selected.

surazo 24-01-2021 10:57

Re: Almanac and Celestial Navigation Calculator
Sean . Really great and amazing work .Thanks to share it with us .Normally we choose to use one program or app and know how to use in a better way and sometime have another as a back up .My guess is to use your app or data sheets as a main and to return and re-learn how to use and old sextant friend .
Thanks again

Apollo366 24-01-2021 15:18

Re: Almanac and Celestial Navigation Calculator
Thank you Sean, works very well, I'll check for other So Pac destinations in the following weeks & let you know if any more are needed.

BTW what was your source of destinations input again? I didn't recognize your reference.

Apollo Wayne

Lodesman 24-01-2021 15:40

Re: Almanac and Celestial Navigation Calculator

Originally Posted by StoneCrab (Post 3326764)
Is it even possible anymore to purchase a current Nautical Almanac?

Goto the sources:


Admiralty has an e-pub option.

SeanPatrick 24-01-2021 23:22

Re: Almanac and Celestial Navigation Calculator

Originally Posted by Apollo366 (Post 3327471)
BTW what was your source of destinations input again? I didn't recognize your reference.

Pareto Software, LLC.

It is also noted on the "Instructions" tab, and at the bottom of the waypoint list on the "Course" tab.


SeanPatrick 25-01-2021 03:54

Re: Almanac and Celestial Navigation Calculator
Here's 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) ˇ sin(dec.2) + cos(dec.1) ˇ cos(dec.2) ˇ 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.

SeanPatrick 27-01-2021 16:15

Re: Almanac and Celestial Navigation Calculator
New website:

Adelie 27-01-2021 16:18

Re: Almanac and Celestial Navigation Calculator

Originally Posted by StoneCrab (Post 3326764)
Is it even possible anymore to purchase a current Nautical Almanac?

I tried last year and couldn't find anyone selling them. I called the local planetarium for a referral and they told me that the pro's just use a computer program.

I think this spreadsheet will be a useful tool.


Midnight Son 27-01-2021 18:41

Re: Almanac and Celestial Navigation Calculator

Originally Posted by SeanPatrick (Post 3330100)

Thank you

GrowleyMonster 29-01-2021 13:15

Re: Almanac and Celestial Navigation Calculator
Very nice! Good to see somebody doing something celestial oriented in this era of touch screen swipers calling themselves navigators. Only two concerns, both kind of minor in the big scheme of things. First it would appear that your spreadsheet uses VB, and won't run natively on a Linux computer. (I might be wrong, haven't tried it) and a LOT of boaty type people are using one or another flavor of Linux these days. Second, one of the big selling points of Celestial is that it is a completely separate and redundant backup system that does not need any of that newfangled electricity stuff to use. Still, I applaud your hard work and I am glad to see you presenting this. I am sure it will be of use to someone out there.

SeanPatrick 30-01-2021 01:05

Re: Almanac and Celestial Navigation Calculator

Originally Posted by GrowleyMonster (Post 3331503)
Very nice!

Thank you.


Originally Posted by GrowleyMonster (Post 3331503)
Only two concerns [...]

Yeah, my ultimate plan is to convert it into a mobile app and/or PC program. Whether or not it will be available for Linux depends on how much work it takes me to port it over. When I started this project, I thought the celestial mechanics would be the hardest part and building the app would be relatively easy. Turns out it's the other way around.

As for not needing electricity, my spreadsheet will calculate a data series for any date and length of time. So, you could print e.g. a table of the Sun's GHA and dec. for each hour of your planned voyage time well in advance. But - let's say your boat actually is hit by lightning and everything including the GPS is fried ... except that one laptop you had stowed away. Wouldn't it be nice if that laptop could save you a lot of the work of navigating the "old" way?

Besides that, tools like my spreadsheet can help people understand and learn celestial navigation. I know it helped me to have similar tools available when I was learning. Today I can reduce a sight probably a dozen different ways. But a computer program is still the method I use the most.


Midnight Son 30-01-2021 06:40

Re: Almanac and Celestial Navigation Calculator
If a program, please post the source on Github.
Thank you:thumb:

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