Celestia plug-in: Ephemerides
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Author:  fenerit [ Sun, 04-01-15, 16:21 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Ephemerides 3.4
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- fix a bug (mine, not of Marco Klunder) within the rise/set routine; minor fixes throughout the routine;
- fix the lacking decimal degrees option for the Earth Rotation Angle;
- fix some wrong parts in comments (a big one within the FCN module, the variable is/was right);

- removed Saturn's magnitude variation ought to the ring's aspect;
- pad signs and zeroes for decimal/sexagesimal degrees outputs; add one decimal float to seconds;
- conformed Sun's north pole PA like the others (CCW, east to celestial north pole's direction);
- due to the print option, the ERA/GSTs will be paused (pause key) also in systemtime mode;
- columned the subpoints because too lengths in sexagesimal mode;
- moved "home" button on the left of the caption bar;
- minor gauges;

- ecliptic, galactic and supergalactic coordinates;
- print on file of the complete object's ephemeris; time span one month step 1 day in tabulated form;
- the ICRF/ITRF quantities does switches in time their units from arcseconds to degrees, for millennia range;

The print button drops down other two buttons; the first from top will print the object's ephemeris in tabulated form, the second will erase the file's content or will format a new empty file either. The print-out files will be named: "ephem_[name-of-the-object].txt". For exoplanets type the [name-of-the-object] will be replaced by [name-of-the-star_name-of-the-exoplanet], in order to avoid the names' overlapping, with the consequence of either erasing the wrong file or appending data about different objects. The default folder in which the files will be placed is: "/extra/ephemerides/print/". This path is customizable within the "ephem.cfg.lua" file. The operation of printing is set in append mode; this mean that it is possible to collect one of more instances of the object's ephemeris within the same file. The simulation times allowed to print are between the 4000 B.C and the 4000 A.D.
The output tables span from the HH:MM:SS of the paused time (peer-user) to the HH:MM:SS one month after, step one-day. The output tables lists also the phase angles and the apparent diameters (of the planets), albeit not present on the Ephemerides' HUD and are on the main Celestia's HUD instead. As it is, the output file is set in English; even though it will show some text in the "locale" language because it will partially borrowed unchanged from the langs. Who wish to translate completely the output file in another language than english, my suggestion is of using the different object's outputs as templates to format on them the headers with respect to the length of words and then copy/paste the text within the "ephemPrint.lua" module at the right places. I do not have planned for near future the insertion of the translateable lines within the lang files, sorry.
Linux and MAC users should change the path conformingly to the proper OS configurations.

- the print on file feature aided me in seeking the overlooked fact that the Saturn's magnitude was unrealistic due to the formula for the ring's aspect; I do not why it doesn't work correctly (maybe a naive error that I'm unable to reckon), hence I've remove it.
- galactic and supergalactic coordinates are displayed for the Sun, stars and DSOs only; for solar system objects they are replaced by the ecliptic coordinates; this short down the menu length a bit;
- printed out values will always be in decimal format;
- the displacement on the left of the "home" button avoids the annoying issue of re-calibrating the observer's position whether pressed since it was along with the others. The spacing between the caption-bar and the first icon on the right is customizable within "ephemCfg.lua"; value in pixels > 0 for longer or < 0 for shorter languages than English. Default = 0. This setting does not change the spacing between the icons.
- Albeit millennia are taken into account to follow the Celestia's simulation, bear in mind however that for some ICRF/ITRF quantities their declared accuracy is very for a range of half a century and not of millennia.
- some text lines within the printed table are abruptly stolen from the JPL HORIZONS site. Hope that guys do not propulse a rocket straight on my head since I'm busy to change the now exaust tube triods of my stereo power amplifier, and without sound I'm a dead man anyhow.
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Print table on now defunct OpenSUSE 12.3 x64 (Kate)

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Author:  fenerit [ Sun, 15-03-15, 14:22 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides


I've decided to add a menu to display some peer-user options acting on variables in real/simulation time (one can see it on the objects' altitudes, refraction, etc. outputs). It will be not memorized on disk and the initial values will be those already set within the config file; but they can be changed when Celestia is running. At least, then, one can set the config. file with its suited values after all, and close to the seasonal average to be successively tuned up on-the-fly at prompt.
The observer altitude is made dynamical now; from zero to the tip of Mt. Everest range; outside this (e.a. in orbit), the "home" altitude is held as the default one on which the computations are done. The real time is then nested with the "true clock" real time - say, synchronizing ERA+GAST+nutation/precession armamentary with the Hour Angle in "classic" longitude mode - therefore one must be forced to switch the option for the simulation time (Time span), if need such config, otherwise the objects will not be "out-there-in-measures", being the time running by system clock. This is different from the previous version by the fact that it is not the ERA/sidereal's items alone which will run independently, but also the hour angle and derivatives: azimuth, altitude and topocentric (now restored conformingly) RA, DEC.
The print options have been moved within the options and its button has been replaced by a "solar energy" display: aka, a solar irradiance model for clear/cloudy sky, accounting for all optical parameters (included semplified Mie aerosol-scattering [Young]) calculated (theoretically) for all Earth's places. It include also the change in irradiance due to the solar eclipses. Unfortunately, although my roughly and fast tests are now at level of catching the moments of start/end of the eclipse, I must still to calculate the obscuration percent to stess definitely the irradiance and therefore all this will not be ready prior the incumbent North Europe solar eclipse of 20 March (BTW, the inspiration for all this). Another question is that the irradiance model is (relatively) simple to code following the papers, but I like to understand a tad more the underlying concepts, so I'm involved in lot of lectures, moreover giving it some formulas as acquired in formalism by remanding to other papers, and from these to another ones and so on.

ephem_opt.png [ 189.24 KiB | Viewed 5987 times ]

Propositions like "the transmittance of aerosol absorptance and scattering" must be either episodes for sit-coms or printed on T-shirts...

Author:  fenerit [ Tue, 17-03-15, 2:12 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides


The user's options menu like:

- Topocentric
- AzimuthModeNorth
- Sexagesimal

will be also memorized on disk when manipulated, so for each Celestia's load are retrieved the last ones set. Home altitude and coordinates are excluded for plains reasons.

Author:  fenerit [ Wed, 18-03-15, 4:04 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

This is a check for the eclipse of 20 March at London.
The values from above are respectively (Watt/m^2):
- the total solar radiation received under clear-sky conditions on horizontal plane at the surface (direct + diffuse);
- the extra-terrestrial solar radiation (normal incidence) on ni-th day of the year (Spencer, 1971), multiplied by (1 - eclipse magnitude).

start eclipse:
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at maximum:
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Author:  fenerit [ Thu, 19-03-15, 2:45 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Just to show one of the problems in which (alas!) I'm involved...
quote from:
B. E. Psiloglou and H. D. Kambezidis - Performance of the meteorological radiation model during the solar
eclipse of 29 March 2006
, pag 4:

During the Earth’s movement around the Sun, Iex varies by approximately ±3.5% of its value at the equinoxes. Iex may
be expressed on the ni-th day of the year as (Spencer, 1971):
Iex = Io * (1.00011 + 0.034221 cos(GAMMA) + 0.00128 * sin(GAMMA) + 0.000719 * cos(2*GAMMA) + 0.000077 * sin(2*GAMMA))

where Io is the solar constant, equal to 1366.1 W/m^2, and GAMMA (in rad) is the day angle, which is given by:
GAMMA = 2 pi * (ni - 1) / 365; ni ranges from 1 (1 January) to 365 (31 December); February is always assumed to
have 28 days.

Now, Iex is the extra-terrestrial solar irradiance and ni is retrived with same function the plugin use for the day of the year, and the result is shown in the screenshots above.
In real, accordingly with:

Robert Leslie Annear - A Comparison of Five Models for Estimating Clear-Sky Solar Radiation

seem that the above polynomial expression is drawn by Spencer 1971 to get the declination of the Sun - not its altitude by which must be multiplied the solar constant Io. That is:

Iex = Io * sin(altitude of sun) * (1AU / distance-earth-sun)^2 -- [the eccentricity correction]

This result does halves the screenshots' values!

Author:  fenerit [ Thu, 19-03-15, 4:06 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Well... solved.
The two are complementary. The "normal incidence" aka the intermediate passage along declination was multiplied by the the cosine of zenith angle; once this latter has been removed, the total irradiance's values matches (a bit less - 283,916 in the first and 54,784 in the second screendump respectively - with the more precise computation through altitude). The extraterrestrial solar irradiance has been framed in a range more conform: 477 in the first and 84,5 in the second screndump respectively. That huge value was my mumble about.

Author:  fenerit [ Thu, 09-04-15, 0:46 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Ephemerides 3.5

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ephem_3.5_2.png [ 84.93 KiB | Viewed 5844 times ]

- interface;
- restored topocentric;
- removed the daily insolation;
- dynamical observer altitude within landmass range;
- some optimizations;

- ICRF/ITRF-based computation (geocentric and topocentric) for all objects in real-time (synch. clock) options;
- LHA always ICRF/ITRF based, even in simulation;
- refraction for independent Sun altitude routine in topocentic (yes) and geocentric (not) mode;
- solar radiation model;
- customization parameters menu;

This time no poem in explications; just do take a look within the "ephemCfg.lua" file before to load Celestia. All remaining settings are customizables from within the plugin itself on the fly.

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Few errata corrige in text comment of the solar model that I've forgot of correcting:
- line 530: read "always topocentric", since no dat are displayed in geocentric mode;
- line 548: read: "on horizontal surface", not "normal incidence", being already multiplied by cos(theta);
- line 638: this is not strictly true, since there are also those measured for Boston; but I found that the same table was different in values amongst papers for some cloud type (typos?);
- line 714: read "the product" of alpha_s as the portion of "sky between the base cloud layer and the ground"

the local function within the solar module named: EPHEM_SOLAR_DAYNUMBER can be deleted.

Author:  fenerit [ Fri, 17-04-15, 20:42 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides


I discovered to have added twice the "equation of the equinoxes" into the GMST :wall: ; being the "equation of the origins" returned as "equinox solution" and not in its polynomial part only, which is the part to be added to the ERA to get the GMST IAU 2006 P03 solution and hence the other sidereal times. This has been fixed and will be part of the next update.
FYI, the next update will be VINTAGE ;)

Author:  fenerit [ Mon, 20-04-15, 1:45 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Ephemerides 3.6 (Vintage version)

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ephem_3.6_vintage_2.png [ 131.6 KiB | Viewed 5769 times ]

- "bug" in doubling the the "equation of equinoxes" from GMST -> GAST;
- Equation of Time's float digit oscillation (due to the nutation);
- pad zero to the seconds for the microarcseconds level quantities in sexagesimal format;
- some issues with the timescale;

- moved the solar model as sub-menu within the Earth's "phenomena" button (removed the icon from the main ones);

- IERS Bulletins C & D (UTC-TAI & DTU1) as sub-menu of the "home" button;

- As for June 31 the difference UTC-TAI will be -36 sec. and also the DUT1 will change, therefore I've add the relevant option to add those values on-the-fly without to deal with the Cfg file. The behaviour added to the DUT1 arrows button could seem weird, but it is the only way in which I was able to avoid the LUA overflow in the passage through zero for step +/- 0.1; such an overflow is not present for the UTC-TAI step +/- 1.0;

- such a kind of interface is due to the fact that I can't give credits to the icon's authors, have been them stored on disk in long time both from the net and from magazines' CD-ROMs, and I no longer remember anything about it. The new "look" could be either fine or ugly, but the icons are created by myself and hence credits no needs to be accomplished.

- A special thanks to Jeff Mack (Jeffrey Stuart MacKinnon) for its AstroClock with which I check the Earth's orientation quantities and sidereal times. 8)

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Author:  fenerit [ Wed, 22-04-15, 2:23 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides


- added aberration and nutation corrections (after) to the precessional routines. Note that corrections for ecliptic coordinates doesn't concerns the latitude being unchanged by nutation; therefore it can be considered as a "bug fix" within the module.

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Author:  fenerit [ Sun, 09-08-15, 11:54 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Seems that for 15 August 2015 will happen this.
In that case one should add to the end of "ephemOffs.lua" the following string:

-- new North Korea Standard Time
ephem_local_timezone_table[231] = "NKST" ephem_offset.NKST = 0.35417 -- North Korea Standard Time

Note that the label "NKST" is guessed, while the time is 9h-0.5 = 8.5/24 = 0.354166666 (rounded to 7, whether those guys does round it...).

Author:  fenerit [ Wed, 21-10-15, 1:46 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

For the vintage version. No comment... :°

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Author:  fenerit [ Fri, 01-01-16, 16:00 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Ephemerides 3.6 (Vintage version) Service Pack 1.0

- fix a missing boolean which occasionally caused the option menu showing at start;

- ADD:
- polar motion prediction based on IERS Bulletin A formulas;
- ecliptic coordinates for the Moon (missing from display);

Languages updated included.

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Author:  fenerit [ Sat, 02-01-16, 17:09 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Thanks to Marco Klunder, is available the complete Dutch language translation.

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Author:  fenerit [ Sat, 20-02-16, 12:46 GMT ]
Post subject:  Re: Celestia plug-in: Ephemerides

Ephemerides 3.6 (Vintage version) Service Pack 1.1

- fix for sexagesimal degree mode.
Pad the minus sign for degree's range [0.0 < d > -1.0] when the minute is < 60.0. This fix lot of latitudinal things for objects closest to the fundamental planes, expecially for alt-az coordinates were geocentric/airless and topocentric/refraction plays a consistent role.

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one file: ephem_coords.lua

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