Odd transient spikes coming off the sun

[Astroman]

Keep in mind first that I grabbed numbers off the top of my head for the velocity of the prominence in question, and perhaps "logarithmic" is an incorrect term. That said, calculation the doppler shift of light is not a straightforward calculation. It depends on the frequency of the light being seen. H-alpha is easier to shift than, say X-rays. (I think I mentioned this before when talking about GRB's somewhere.) The main idea I was trying to illustrate is, if the velocity of the prominence is high enough, it will shift its frequency enough to "miss" the narrow window of your filter and you'll only see it if it drops in velocity enough to hit your window.

The entry angle bit is trickier to explain. The etalon filter works because it bounces light back and forth internally before passing the selected frequency. The frequency is selected by several factors including the distance between reflective surfaces and the angle at which the light enters. Since prominences are made up of ionized plasma floowing magnetic filed lines, the angle at which the plasma travels along the field line may prevent it entering the filter at the proper angle, thus being reflected away rather than passed through. So, if the magnetic filed line of this particular prominence was tilted more one way than the other, coupled with the velocity and doppler shift, it may have been visible in more frames.

[daz]

Hey, a lot of this makes sense to me - well, a good size chunk anyway!

Looks like some of this stuff is at last sinking in!!!