Solar Granulation

[pbyrne]

Hi all

I'm new to white light solar observing, with sunspot activity low at the moment, I would like to try for granulation.  Under what conditions is granulation visible?

My setup is 120mm Evostar with Lacerta Herschel wedge and Baader Solar Continuum filter.

Thanks

Paul

[Moonshane]

When seeing is good basically. Perhaps 100x magnification.

[John]

From what I understand (Stu knows a lot about this) seeing true granulation is actually quite difficult. There is a texture visible across the white light solar surface quite often visible but I'm not sure that this is actually granulation ?

Perhaps Stu will chip in soon and explain ?

[bish]

25 minutes ago, John said:

From what I understand (Stu knows a lot about this) seeing true granulation is actually quite difficult. There is a texture visible across the white light solar surface quite often visible but I'm not sure that this is actually granulation ?

Perhaps Stu will chip in soon and explain ?

I always thought it was granulation you could see mainly close to the limb.  Interested to see if this isn't actually the case.

[David Smith]

I use an Evostar 120, Lunt 1.25" wedge and Solar Continuum / single polarising filter. With decent seeing I can usually see granulation with my Revelation 15mm (~70x). I find patience is key, a quick glance will not show it but persevering and adjusting the brightness with the polariser will often bring out the detail.

1 minute ago, bish said:

I always thought it was granulation you could see mainly close to the limb.  Interested to see if this isn't actually the case.

That's faculae (bright areas).

[bish]

6 minutes ago, David Smith said:

I use an Evostar 120, Lunt 1.25" wedge and Solar Continuum / single polarising filter. With decent seeing I can usually see granulation with my Revelation 15mm (~70x). I find patience is key, a quick glance will not show it but persevering and adjusting the brightness with the polariser will often bring out the detail.

That's faculae (bright areas).

Ah yes I definitely see faculae, must be getting confused.

(As a Vikings fan it looks like I wont be teasing the Bears this season!)

[Stu]

Not sure about expert, perhaps just a cunning parrot who can repeat what he is told

On days of good seeing and at lowish power you can generally see a mottled effect over the surface of the sun, which to me is more pronounced towards the centre where you are effectively looking straight into the cells. Often refered to a granulation, this has been explained to me more as 'macro-granulation' and is I guess due to the variation in distribution density of the unseen granulation cells.

The cells themselves are very small, about 1 to 2 arc seconds across (The same as the separation between tight double stars for instance). To see these properly needs excellent seeing and high power. When things are good, I tend to use up to x200 or perhaps more and at this level you can actually see the individual cells. They do change gradually over a period of tens or minutes so even if the sun is blank they is sometimes some interest to be had.

Features like faculae which are the brighter thread-like structures tend to be seen nearer the limb as the limb darkening increases the contrast making them visible.

EDIT note that just as the double double can be seen at say x70 or less, with splits of around 2.3 ish arc seconds, but looks much more separated at higher power, so the granulation cells themselves open up more when viewed at higher power.

[bish]

Found this with a quick google search. This chap seems to be able to see some granulation with his set up.

https://www.skyandtelescope.com/observing/celestial-objects-to-watch/sun/sun-white-light-guide-nearest-star/

[Stu]

4 minutes ago, bish said:

Found this with a quick google search. This chap seems to be able to see some granulation with his set up.

https://www.skyandtelescope.com/observing/celestial-objects-to-watch/sun/sun-white-light-guide-nearest-star/

That's a great timelapse video, shows the kinds of motions that can be detected if you view for ten or fifteen minutes with excellent seeing.

[David Smith]

12 minutes ago, bish said:

Ah yes I definitely see faculae, must be getting confused.

(As a Vikings fan it looks like I wont be teasing the Bears this season!)

Makes a change for the Bears fan to have the upper hand!

[bish]

Just now, Stu said:

That's a great timelapse video, shows the kinds of motions that can be detected if you view for ten or fifteen minutes with excellent seeing.

Do you have any floaters Stu? I find they are really off putting white light viewing.

[bish]

Just now, David Smith said:

Makes a change for the Bears fan to have the upper hand!

You deserve  a break!

[Stu]

3 minutes ago, bish said:

Do you have any floaters Stu? I find they are really off putting white light viewing.

I do indeed, which is why I exclusively binoview when solar observing these days. It doesn't eliminate the floaters but does make them much more manageable even at high powers.

[bish]

15 minutes ago, Stu said:

I do indeed, which is why I exclusively binoview when solar observing these days. It doesn't eliminate the floaters but does make them much more manageable even at high powers.

That's useful to know. I have thought about binoviewers in the past (before my eyes were full of floaters). Think I may give them a try.