Kstars bugs I can work on

Sat Sep 2 14:43:25 UTC 2017

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
>>
>
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