Download link

The Navigation Spreadsheets suite is available for free download:

https://github.com/pmh099/navigation-spreadsheets

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Lunar distance presetting

Today I conducted a quick exercise presetting a sextant to the Sun-Moon near-limb distance (no refraction corrections).
Sextant: Astra III Professional with the 7×35 Celestaire telescope
Calculations with Navigation Spreadsheets (screenshots attached)

Date: May 26, 2019
Local time: 9:25 am, U.S. Mountain Daylight Time
Universal Time: 15:25
Location: 35° 53’ N, 106° 19’ W

Sun:
GHA: 51° 59.4’
Dec: N 21° 08.8’
SD: 15.8’

Moon:
GHA: 137° 19.1’
Dec: S 13° 17.7’
SD: 14.8’
HP: 54.3’

Topocentric lunar distance: 91° 07.0’
Subtracting the sum of the two semidiameters: 30.6’
Presetting the sextant to: 90° 36.4’

Then, I pointed the sextant at the Moon and soon the Sun appeared right on top of Moon’s limb, as expected. I did not even check the index error beforehand (the sextant has been sitting in its box for months). The whole procedure lasted less than 15 minutes; doing this write-up took somewhat longer than that. 🙂  A good result overall.sunmoonld_prec

Astron 2.00 release

In 2015 “an anonymous benevolent user” of the original Navigation Spreadsheets combined several of them into a single unit named Astron to provide a much more user friendly interface and functionality.

In 2018 version 2.00 has been rewritten as a web page and can be run online on recent versions of popular browsers and, for seafarers, can also be run offline with Chrome, Firefox, and Opera.

https://vigilanceofbrixham.co.uk/Astron/Astron.html

This first release is Beta version. Coding in Javascript has enabled some improvements and additions. There is now a sky map addition to the Planner section, a sight log, a sight plotter, and an extended lunar section. For those not wishing to change from the former spreadsheet version, Astron version 1.15 is the latest version which remains supported but future developments are only intended for version 2.

Both versions, and the extensive user notes can be accessed from

https://vigilanceofbrixham.co.uk/Astron/

Astron200

New releases and updates

In 2015 “an anonymous benevolent user” of the original Navigation Spreadsheets combined several of them into a single unit to provide a much more user friendly interface and functionality. The result (named “Astron“) is hereby released with its creator’s consent.

Astron_V1.0To download, visit:

GitHub

Original website

During this development process a small error (less than 1’) in the GHA calculation was discovered and corrected in all almanac spreadsheets. We therefore recommend downloading the latest version of the suite; in particular, the spreadsheets: aries_stars, sun, mercury, venus, moon, mars, jupiter, saturn, uranus, neptune, what_star, polaris, polaris_lha.