Feats where only part of a planet/star is shown

[Arrogant_Schmuck]

Hello all, if there's a feat where something happens near Earth, the sun, etc and you're trying to use said planet/star to scale, but only part of it is shown, how can you calculate that?

I found this calc which has a similar situation, is that a reliable method of fixing this problem?

Thanks in advance

 

[DontTalkDT]

It as a usual way to do things, if you refer to the drawing a circle thing.

However, one should pay attention to perspective, cause things besides the star/planet could often also be closer to the viewer than the celestial object in question in which case the scaling won't work.

 

[Arrogant_Schmuck]

This is the feat I'm looking to use this method for

http://i.imgur.com/bh6aJiV.jpg

 

[DontTalkDT]

I think for that it would be fine.

 

[Arrogant_Schmuck]

Also, how can I get a value using the height of the explosion, if it's possible?