Kstars bugs I can work on

Sun Sep 3 09:51:25 UTC 2017

So I continued investigating this, and here are a couple of observations.

1. If I set location to Greenwich, then all heliocentric ecliptic
coordinates become valid! So there is a time component to this (Julian
days?) that offsets the values.
2. Even if heliocentric ecliptic coordinates are correct, the geocentric
ecliptic coordinates are wrong. Why? Because Earth ecliptic longitude and
latitude are inaccurate.

EDIT: As I am writing this, I found line 107 of KSNumbers with a note on
this. We seem to be using a constant for ecliptic longitude of Earth
perihelion. It's set as 102.94719

I used JPL Horizons system to calculate current value for Sep. 4th, 2017
and it is 104.8089842092676

Earth orbital elements MUST be updated periodically then. The Earth
ecliptic coordinate reported by Horizons is:

Long: 341.4178043
Lat: 0.0004911

While in KStars, it is:

Long: 341.6696035955447
Lat: -5.294750917241062e-5

Once I manually correct Earth's ecliptic coordinates, the asteroid location
is pretty accurate. More investigation is required.

Regards,
Jasem

On Sat, Sep 2, 2017 at 5:43 PM, Jasem Mutlaq <mutlaqja at ikarustech.com>
wrote:

> Hi Robert,
>
> Oh!! I am working on this bug now. I'm not getting anywhere with it so
> far. I use JPL Horizons system to check the orbital parameters:
> https://ssd.jpl.nasa.gov/horizons.cgi
>
> I am calculating all orbital elements and comparing it with JPL values
> starting from Mean Anamoly, then True Anamoly..etc. Here are JPL values
> from Horizon:
>
> JPL Heliocentric Orbital Elements
>
> $$SOE
> 2457998.500000000 = A.D. 2017-Sep-02 00:00:00.0000 TDB
>  EC= 4.232744439134506E-01 QR= 1.020269859137170E+00 IN= 2.215206298911301E+01
>  OM= 3.360953610775869E+02 W = 2.784196493952410E+01 Tp=  2458020.936332046986
>  N = 4.188758125005247E-01 MA= 3.506019631843183E+02 TA= 3.348867725600903E+02
>  A = 1.769073432535834E+00 AD= 2.517877005934499E+00 PR= 8.594432747284709E+02
> 2457999.500000000 = A.D. 2017-Sep-03 00:00:00.0000 TDB
>  EC= 4.232901835419896E-01 QR= 1.020263438440515E+00 IN= 2.215145437416221E+01
>  OM= 3.360952684752951E+02 W = 2.784456004960867E+01 Tp=  2458020.938336936291
>  N = 4.188626190102440E-01 MA= 3.510202820436723E+02 TA= 3.359645930024024E+02
>  A = 1.769110580961994E+00 AD= 2.517957723483473E+00 PR= 8.594703457918157E+02
> $$EOE
>
> JPL Heliocentric Ephemeris
>
> **********************************************************************************************************************************************************
>  Date__(UT)__HR:MN     R.A.__(a-apparent)__DEC hEcl-Lon hEcl-Lat               r        rdot            delta      deldot    ObsEcLon    ObsEcLat Tru_Anom
> **********************************************************************************************************************************************************
> $$SOE
>  2017-Sep-02 00:00     22 56 46.97 +08 13 17.0 338.6177   1.0264  1.049795367593  -4.4410821 1.04979536759279  -4.4410821 338.6176978   1.0264441 334.8811
>  2017-Sep-03 00:00     23 00 48.31 +08 38 34.4 339.6187   1.4332  1.047281909825  -4.2622642 1.04728190982466  -4.2622642 339.6187413   1.4332183 335.9589
> $$EOE
>
> JPL Vector Data (Rectangular Heliocentric Coordinates):
>
> $$SOE
> 2457998.500000000 = A.D. 2017-Sep-02 00:00:00.0000 TDB
>  X = 9.774013251109912E-01 Y =-3.825877896251375E-01 Z = 1.884479352236287E-02
>  VX= 4.155441472803211E-03 VY= 1.801646315290931E-02 VZ= 7.391156829632851E-03
>  LT= 6.063034210721955E-03 RG= 1.049781831306806E+00 RR=-2.564399485651484E-03
> 2457999.500000000 = A.D. 2017-Sep-03 00:00:00.0000 TDB
>  X = 9.814311564582442E-01 Y =-3.645229326093622E-01 Z = 2.623313001987751E-02
>  VX= 3.903753134260795E-03 VY= 1.811258715727221E-02 VZ= 7.385185521988751E-03
>  LT= 6.048521037259282E-03 RG= 1.047268953218673E+00 RR=-2.461117456681675E-03
> $$EOE
>
>
> They precess all values while we don't precess anything in asteroid class.
> In comets we precess OM, so I added that back into asteroid class to
> precess OM (Longitude of the Ascending Node). Here is KStars values for Sep
> 2nd 00:00:00:
>
> EC = 0.4233003617604261
> W = 27.84698664318219
> MA = 350.5485275538136
> E = 343.7697842874328 (Not shown in JPL above, the Eccentric Anamoly)
> TA = -25.252507942167078 = 334.747492057832922
> IN = 22.1507826948212
> A = 1.769132449016887
> OM = 336.095126120893 (After I precessed it, it's not in code yet)
> r = 1.0510131460163505
>
> You can see we have some differences in the true anamoly and by extension
> sun distance. There are small differences in other elements, but these two
> stand out leading to inaccurate heliocentric ecliptic coordinates and
> eventually to wrong geccentric J2000/JNow coords. At first glance it
> appears that the eccentric anamoly value might be inaccurate, but we use
> the same iterative algorithm we already use in the comets class. Comets can
> also be inaccurate but not as bad as this case.
>
> I think it might be a good idea to add another backend for this, we could
> be utilizing JPL Development Ephemeris (e.g. 406+) for solar system
> calculations. Another option is to switch to MPC for data source, but I'm
> not sure what difference will this make.
>
> Regards,
> Jasem
>
>
> On Sat, Sep 2, 2017 at 3:45 PM, robert <robert at navsoft.plus.com> wrote:
>
>> Great - I'm starting with *Bug 384276*
>> <https://bugs.kde.org/show_bug.cgi?id=384276> - [kstars 2.8.2] Wrong
>> placement of asteroid Florence
>>
>> R
>>
>> On 02/09/17 13:05, Jasem Mutlaq wrote:
>>
>> Hi Robert,
>>
>> You can start by submitting patches to me, and then later on we'll create
>> you an account on the system to handle it directly. So yeah clone KStars,
>> then when you have a fix, run git diff and send me a patch.
>>
>> Thanks for the help!!
>>
>> Regards,
>> Jasem
>>
>>
>> On Sat, Sep 2, 2017 at 2:38 PM, robert <robert at navsoft.plus.com> wrote:
>>
>>> Hi Jasem,
>>>
>>> I've had a look. Reminds me of when I worked for a living;  but very
>>> happy to help.
>>>
>>> 1. I guess I need, at least, permission to assign myself the bugs that I
>>> am working on.
>>>
>>> 2. Is the source at "git clone git://anongit.kde.org/kstars"?
>>>
>>> 3. How should I submit proposed mods? Published KDE procedures?
>>>
>>> Robert
>>>
>>
>

-- 
Best Regards,
Jasem Mutlaq
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