Comet C/2014 Q2 is not visible

[Nick Fedoseev]

After importing comet from MPC, it's position can be found with F3, but no actual object is shown.

Drawing is canceled in the following line :
 if (!orbit->objectDateValid(core->getJDay())) return; // don't draw at all if out of useful date range. This allows having hundreds of comet elements.
[comet.cpp, line 463]

Further investigations tell us that time_at_pericenter for this object has negative value.

The comet is added to the ssystem.ini as usual:

[c2014q2(lovejoy)]
orbit_SemiMajorAxis = 582.1349
orbit_ArgOfPericenter = 12.3952
orbit_Epoch = 2457000.5
slope_parameter = 8.4
orbit_AscendingNode = 94.9754
type = comet
orbit_MeanAnomaly = 359.9963
name = C/2014 Q2 (Lovejoy)
albedo = 0.04
orbit_MeanMotion = 7.02e-05
orbit_Eccentricity = 0.997783
tex_map = nomap.png
color = 1.0, 1.0, 1.0
absolute_magnitude = 4
orbit_Inclination = 80.3029
parent = Sun
lighting = false
coord_func = comet_orbit
radius = 5

There are two possible temporary solutions:
- add the following line:
   orbit_good=100000000000

- replace
type = comet
with
type = asteroid

[gzotti (georg-zotti)]

I cannot reproduce this in current trunk, comet is nicely rendered. What version do you use?

[Alexander Wolf (alexwolf)]

Nick, how exactly you added comet?

Georg, it maybe related to bug #1358230

[Nick Fedoseev (nick-ut2uz)]

In order to reproduce the bug, just append the above mentioned section to the ssystem ini and restart stellarium.

I did not check the exact position, but it appears where expected. The position does not change after replacing type=comet with type=asteroid.

The same is for 15P/Finley. Adding magic orbit_good=100000000000 manually lets comet be visible.

[15pfinlay]
name = 15P/Finlay
orbit_ArgOfPericenter = 347.5534
absolute_magnitude = 12
orbit_Eccentricity = 0.720184
orbit_MeanAnomaly = 357.2675
lighting = false
albedo = 0.04
slope_parameter = 4
orbit_Inclination = 6.799
orbit_Epoch = 2457000.5
color = 1.0, 1.0, 1.0
parent = Sun
orbit_SemiMajorAxis = 3.487658
radius = 5
type = comet
orbit_AscendingNode = 13.7777
coord_func = comet_orbit
tex_map = nomap.png
orbit_MeanMotion = 0.1513224

[Nick Fedoseev (nick-ut2uz)]

For those who can compile stellarium from sources, the bug easily cured by commenting out the above mentioned line 463 in comet.cpp. This is not a correct solution, another criteria shold be developed for this feature. I do not have enough knowledge at the moment to generate such criteria.

[Nick Fedoseev (nick-ut2uz)]

Forgot to say, both comets were added by ssystem editor plugin, with online MPC search. The program version is 0.13.2 RC1.

[gzotti (georg-zotti)]

I think Alexander is right. I imported the elements from MPC list import, not the online search. Comet element sets should NOT have orbit_MeanAnomaly or orbit_MeanMotion entries, these don't make much sense for most comets!

So this is a duplicate of the bug which Alexander mentioned above. Do NOT comment away the test in line 463, or you risk a massive slowdown if you have many element sets.

These would be the elements if imported via list import, and these work:

[c2014q2%28lovejoy%29]
orbit_Inclination=80.3027
slope_parameter=8.4
coord_func=comet_orbit
parent=Sun
orbit_ArgOfPericenter=12.3949
orbit_PericenterDistance=1.290357
lighting=false
radius=5
type=comet
dust_brightnessfactor=1.5
absolute_magnitude=4
name=C/2014 Q2 (Lovejoy)
orbit_Eccentricity=0.997796
orbit_good=267
orbit_TimeAtPericenter=2457052.56909722
albedo=0.1
orbit_AscendingNode=94.9755
color=1.0, 1.0, 1.0
dust_lengthfactor=0.4
dust_widthfactor=1.5
tex_map=nomap.png

[15pfinlay]
type = comet
radius = 5
orbit_good = 176
absolute_magnitude = 12
dust_brightnessfactor = 1.5
name = 15P/Finlay
orbit_Inclination = 6.799
dust_lengthfactor = 0.4
coord_func = comet_orbit
orbit_ArgOfPericenter = 347.5531
orbit_PericenterDistance = 0.975903
albedo = 0.1
orbit_TimeAtPericenter = 2457018.55689815
dust_widthfactor = 1.5
lighting = false
orbit_AscendingNode = 13.7777
tex_map = nomap.png
color = 1.0, 1.0, 1.0
slope_parameter = 4
parent = Sun
orbit_Eccentricity = 0.720178

[Alexander Wolf (alexwolf)]

Georg, we can apply orbit_good parameter to calculations only for tails and coma - and calculate position for core of the comet in any time. Maybe you have a free time for look to both reports?

[Nick Fedoseev (nick-ut2uz)]

It's a pity that the bug report was just deleted

It is definitely NOT a duplicated bug as it describes not a position error,
but the bug of filtering, so actual object is not drawn at all. The
position is correct.

I understand the meaning of the line 463, but I prefer slow drawing instead
of no drawing at all.
But practically I played with hundreds of objects with no visible
performance degradation. Now I need just a few comets,
Especially C/2014 Q2 and 15P/Finlay, the brightest ones on the sky. But I
do not see them both due to the above mentioned line 463.

I and not the only person who meets that problem, so wrote about the
temporary solution.

The filtering rule definitely must be changed.

2014-12-25 12:19 GMT+02:00 gzotti <email address hidden>:

> *** This bug is a duplicate of bug 1358230 ***
> https://bugs.launchpad.net/bugs/1358230
>
> I think Alexander is right. I imported the elements from MPC list
> import, not the online search. Comet element sets should NOT have
> orbit_MeanAnomaly or orbit_MeanMotion entries, these don't make much
> sense for most comets!
>
> So this is a duplicate of the bug which Alexander mentioned above. Do
> NOT comment away the test in line 463, or you risk a massive slowdown if
> you have many element sets.
>
> These would be the elements if imported via list import, and these work:
>
>
> [c2014q2%28lovejoy%29]
> orbit_Inclination=80.3027
> slope_parameter=8.4
> coord_func=comet_orbit
> parent=Sun
> orbit_ArgOfPericenter=12.3949
> orbit_PericenterDistance=1.290357
> lighting=false
> radius=5
> type=comet
> dust_brightnessfactor=1.5
> absolute_magnitude=4
> name=C/2014 Q2 (Lovejoy)
> orbit_Eccentricity=0.997796
> orbit_good=267
> orbit_TimeAtPericenter=2457052.56909722
> albedo=0.1
> orbit_AscendingNode=94.9755
> color=1.0, 1.0, 1.0
> dust_lengthfactor=0.4
> dust_widthfactor=1.5
> tex_map=nomap.png
>
>
> [15pfinlay]
> type = comet
> radius = 5
> orbit_good = 176
> absolute_magnitude = 12
> dust_brightnessfactor = 1.5
> name = 15P/Finlay
> orbit_Inclination = 6.799
> dust_lengthfactor = 0.4
> coord_func = comet_orbit
> orbit_ArgOfPericenter = 347.5531
> orbit_PericenterDistance = 0.975903
> albedo = 0.1
> orbit_TimeAtPericenter = 2457018.55689815
> dust_widthfactor = 1.5
> lighting = false
> orbit_AscendingNode = 13.7777
> tex_map = nomap.png
> color = 1.0, 1.0, 1.0
> slope_parameter = 4
> parent = Sun
> orbit_Eccentricity = 0.720178
>
>
> ** This bug has been marked a duplicate of bug 1358230
> Wrong import of comet data by ssystem editor
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1405460
>
> Title:
> Comet C/2014 Q2 is not visible
>
> Status in Stellarium:
> Incomplete
>
> Bug description:
> After importing comet from MPC, it's position can be found with F3,
> but no actual object is shown.
>
> Drawing is canceled in the following line :
> if (!orbit->objectDateValid(core->getJDay())) return; // don't
> draw at all if out of useful date range. This allows having hundreds of
> comet elements.
> [comet.cpp, line 463]
>
> Further investigations tell us that time_at_pericenter for this obje...