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GeneralRe: any good introduction on Astronomical Ephemeris? Pin
David O'Neil12-Feb-23 18:02
professionalDavid O'Neil12-Feb-23 18:02 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
jmaida12-Feb-23 18:38
jmaida12-Feb-23 18:38 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
David O'Neil12-Feb-23 18:47
professionalDavid O'Neil12-Feb-23 18:47 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
jmaida13-Feb-23 11:10
jmaida13-Feb-23 11:10 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
David O'Neil13-Feb-23 16:26
professionalDavid O'Neil13-Feb-23 16:26 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
jmaida13-Feb-23 16:54
jmaida13-Feb-23 16:54 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
Southmountain14-Feb-23 18:55
Southmountain14-Feb-23 18:55 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
Chris C-B11-Feb-23 20:20
Chris C-B11-Feb-23 20:20 
I have written several ephemerides over the years, the first being for an HP75C, using the 'Low-precision formulae for planetary positions' by van Flandern and Pulkkinen (Astrophysical Journal Supplement Series, vol. 41, Nov. 1979, p. 391-411). The paper provides a good introduction to the general problems of ephemerides, and the stated accuracy of +/- one minute of arc is extremely conservative, and for the current era +/- six seconds of arc is realistic. This ephemeris also calculates the 'First point of Ares', enabling star positions to be computed. I used this method to navigate my small yacht by sextant from Southampton UK to Pireaus Greece, with my worst landfall being one third of a nautical mile out. That was in pre-GPS days.

A more accurate methodology, but also much more compute intensive, is Pierre Bretagnon's VSOP82, subsequently developed and refined to VSOP87. The raw data tables which make the basis for the computations are out there on the web somewhere, I'm sure. When written into a program, it is spritely enough on a PC, but might tax all but top-end mobile devices.

A very good source of foundational information is the US Navy's Nautical Almanac, particularly in the 'Explanatory Supplement', a separate publication. Any year will do. Also, get a thorough understanding of the 'equation of time', as it occurs in just about every ephemeris calculation.

A couple of years ago I rewrote my original HP75C program to run on Android, and expanded it to cover not just the sun, moon, six navigational planets, fifty-eight navigational stars and Polaris, but included all ten thousand stars visible to the naked eye (given very good eyes and excellent viewing conditions Shucks | :-\ ). Even on an old Android phone it runs fast enough to be useful, although the virtual graphical sextant 'scope view is distinctly laggardly when scanning the sky.
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
Southmountain14-Feb-23 18:51
Southmountain14-Feb-23 18:51 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
Gerry Schmitz12-Feb-23 7:00
mveGerry Schmitz12-Feb-23 7:00 
GeneralRe: any good introduction on Astronomical Ephemeris? Pin
Southmountain14-Feb-23 18:53
Southmountain14-Feb-23 18:53 
Generalworldle 386 Pin
jmaida11-Feb-23 15:15
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GeneralWordle 603 Pin
StarNamer@work11-Feb-23 14:54
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GeneralRe: Wordle 603 Pin
Amarnath S11-Feb-23 15:22
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GeneralRe: Wordle 603 Pin
Sandeep Mewara11-Feb-23 17:49
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GeneralRe: Wordle 603 Pin
OriginalGriff11-Feb-23 19:00
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GeneralRe: Wordle 603 - two for me Pin
pkfox11-Feb-23 21:21
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GeneralRe: Wordle 603 Pin
Cp-Coder12-Feb-23 2:26
Cp-Coder12-Feb-23 2:26 
GeneralRe: Wordle 603 Pin
Jeremy Falcon12-Feb-23 12:23
professionalJeremy Falcon12-Feb-23 12:23 
GeneralWordle 603 3/6 Pin
jmaida12-Feb-23 14:22
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GeneralHappy birthday... Pin
Ravi Bhavnani11-Feb-23 13:33
professionalRavi Bhavnani11-Feb-23 13:33 
GeneralRe: Happy birthday... Pin
dandy7212-Feb-23 4:24
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GeneralI dodged a bullet - the message that made my day Pin
honey the codewitch11-Feb-23 12:29
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GeneralRe: I dodged a bullet - the message that made my day Pin
Ron Anders11-Feb-23 14:44
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GeneralRe: I dodged a bullet - the message that made my day Pin
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