Artifacts in rendering of Mercury in the Sun

[Alexander Wolf]

Original report: http://www.astronomy.ru/forum/index.php/topic,21983.msg3523293.html#msg3523293

Translated version: I tried to simulate the Transit of Mercury on May 9 this year. You need make to strong zooming to see the Mercury's black dot. When he has small zoom level you can see white dot, if you increase zoom level more - gray dot, and only when the Sun will twice as wide of screen - black. The latest beta of Stellarium was used.

AW: I can reproduce the issue on series 0.13 and 0.14 also.

[gzotti (georg-zotti)]

This is the "halo" whis is necessary to see the planet when zoomed out. I already tried rendering it before the planet, but then you create a black dot with the 3d planet.
We could add another special case for "inner planet" (depends on observer`s planet of course) to not render halo if inside solar disk. Other idea?

[Tanmoy Saha (t4saha)]

Halo brightness = halo brightness *(1 - phase)

So when planet is in front of sun disk, its phase is 1 and halo brightness will be 0. So halo will not be visible.

[gzotti (georg-zotti)]

That's not as easy. it will then likely already be invisible when 15 degrees away from the sun. Rather a sharp test: "if angular distance < visible solar radius"...
The problem is almost invisible if the atmosphere is switched on and/or you zoom in far enough.

[Alexander Wolf (alexwolf)]

Just an important note: same problem with halo can be visible for moons, when they between planet and observer.

[Alexander Wolf (alexwolf)]

A fix has been committed as revision 8224 of the trunk branch of Stellarium's Bazaar repository at Launchpad: http://bazaar.launchpad.net/~stellarium/stellarium/trunk/revision/8224 and as revision 8052 of the 0.14 branch of Stellarium's Bazaar repository at Launchpad: http://bazaar.launchpad.net/~stellarium/stellarium/0.14/revision/8052