SOHO Lasco C2 Question

So....quick question for anyone that has the answer....how quickly will an object move across Lasco C2 field of view? It seems most move out of it every frame. Just wondering as there is a sequence of 2 days where 4 objects move in unison across the field of vision of the camera and I have never seen anything take 2 days to move from the field of vision. Can anyone explain?

I can't post the actual movie of it I don't think, but if you do a search on SOHO site under data/archived movies for 2015-09-20 to 2015-09-22 and step through it, they start at the very first frame, one is just above and to the left of the sun and one is near the bottom left just above the time stamp. As those go through the field of vision, there is another that follows about middle of the screen left of the sun and a bit fainter, then a final one appears near bottom left as the first two are about to leave the right side of the screen.

Wondering if those are planets or just REALLY slow moving objects.

Link to search: SOHO search

Based on their current positions, I'm going with Venus, Mars, Jupiter, and Mercury respectfully.

That's the only objects I can think of that would move that slowly across the field of view.

originally posted by: wshadow1
Based on their current positions, I'm going with Venus, Mars, Jupiter, and Mercury respectfully.

That's the only objects I can think of that would move that slowly across the field of view.

I thought they might be planets, but I thought they showed up a LOT brighter in the field of view, and these still took over 2 days to cross.....

a reply to: Vasa Croe

There are ways to simulate the SOHO's field of view using various planetarium software. I think ngchunter can do this, so looking forward to his analysis.

SOHO spacecraft "sits" in the L1 point, which is directly on the line between Earth and the Sun. Therefore, if I understand correctly, SOHO's view of the Sun and space around it is basically from the same angle as an observer's on Earth.

I have looked in Stellarium for what happens around the Sun on those dates. The planets Mercury and Jupiter are the closest to the Sun right now, but they are too far away to be seen in those LASCO C2 frames, and they move much slower.

One of my guesses is that those are stars, and the perceived motion is simply due to SOHO orbiting the Sun.

You are much more likely to spot planets in the LASCO C3 frames, as they are more wide-angle. In fact, if you run a LASCO C3 movie for 20-22 Sept, you'll see the background stars slowly move in the same direction as the points of light you posted about.

Verdict - those are stars.

P.S. I think I can even identify the four stars that you mention:
* Moving across the top of the Sun is Beta Virginis (β Vir), traditionally named Zavijava or Alaraph.
* Moving below the Sun is Upsilon Leonis (υ Leo).
* The faint star moving through the middle is IQ Vir, also known by a bunch of catalogue names like HIP 58002.
* Appearing from the left near the end of the movie is Eta Virginis (η Vir), traditionally named Zaniah.

Gotta love Stellarium!

originally posted by: wildespace
a reply to: Vasa Croe

There are ways to simulate the SOHO's field of view using various planetarium software. I think ngchunter can do this, so looking forward to his analysis.

SOHO spacecraft "sits" in the L1 point, which is directly on the line between Earth and the Sun. Therefore, if I understand correctly, SOHO's view of the Sun and space around it is basically from the same angle as an observer's on Earth.

I have looked in Stellarium for what happens around the Sun on those dates. The planets Mercury and Jupiter are the closest to the Sun right now, but they are too far away to be seen in those LASCO C2 frames, and they move much slower.

One of my guesses is that those are stars, and the perceived motion is simply due to SOHO orbiting the Sun.

You are much more likely to spot planets in the LASCO C3 frames, as they are more wide-angle. In fact, if you run a LASCO C3 movie for 20-22 Sept, you'll see the background stars slowly move in the same direction as the points of light you posted about.

Verdict - those are stars.

P.S. I think I can even identify the four stars that you mention:
* Moving across the top of the Sun is Beta Virginis (β Vir), traditionally named Zavijava or Alaraph.
* Moving below the Sun is Upsilon Leonis (υ Leo).
* The faint star moving through the middle is IQ Vir, also known by a bunch of catalogue names like HIP 58002.
* Appearing from the left near the end of the movie is Eta Virginis (η Vir), traditionally named Zaniah.

Gotta love Stellarium!

Thanks for the excellent information AND for taking the time to actually plug in the dates and see what I was asking about....that is a rare quality on ATS these days...

Much appreciated!