Granulation

[Littleguy80]

I'm still new to Solar observing and am only observing in white light. I've heard the term granulation which makes me think of lots of small points. I've been observing over lunch and what observe is more like subtle variations across the disc. Lighter and darker areas as opposed to fine points. I don't think is coming from poor seeing. Is this what's described as granulation? My Herschel wedge includes a continuum type filter which I've read makes the granulation more obvious.

[Stu]

12 minutes ago, Littleguy80 said:

I'm still new to Solar observing and am only observing in white light. I've heard the term granulation which makes me think of lots of small points. I've been observing over lunch and what observe is more like subtle variations across the disc. Lighter and darker areas as opposed to fine points. I don't think is coming from poor seeing. Is this what's described as granulation? My Herschel wedge includes a continuum type filter which I've read makes the granulation more obvious.

Neil, I think a more appropriate term for what you are seeing is Macro-granulation. I have Ken (Merlin66) to thank for understanding this more correctly. Basically you are seeing the variation in density of the granulation cells across the surface of the sun.

To properly see the cells themselves requires high power and excellent seeing. If i recall correctly they are around 1 to 2 arc seconds across, so powers of x100 and more help to open them up, similar to a close double star i guess.

I've occasionally had fabulous views at over x200 in the Tak with binoviewers where you can really see the individual cells, and actually see them change over relatively short periods as they don't last that long.

[Littleguy80]

Brilliant. Thank you for the explanation. That's exactly what I needed. I'll pop an ortho in see what I can pick up

[Davey-T]

As Stu said more visible at higher power, have a look at some WL close ups in the solar imaging section ( Freddies are good examples ) to see how it looks.

Dave

[Littleguy80]

17 minutes ago, Davey-T said:

As Stu said more visible at higher power, have a look at some WL close ups in the solar imaging section ( Freddies are good examples ) to see how it looks.

Dave

Thanks Dave. Found some good close ups from Freddie on AR's where you can see the granulation around the AR. Now for another look through the scope to see what I can see!

[Littleguy80]

I'm pretty confident that I'm seeing macro-granulation (thanks Stu/Ken for correcting my terminology!). I used my 6mm BGO with the Baader VIP. The VIP has an extra T2 extension tube added so I think the magnification was around 186x. I wasn't able to pick anything out that appeared as individual cells. Could be seeing, could be inexperience. Either way, at least I have a better idea of what I'm looking for now

[Piero]

Agree with Stu. 

And above 300x they start showing differences in morphology. With the Tak 100 DF the HR 2.4 really kicks, and when the seeing is excellent, also the barlowed 3.4mm.

[tico]

Hello,

What is the minimum aperture to see the solar granulation?
Thank you
Tico

[Stu]

1 minute ago, tico said:

Hello,

What is the minimum aperture to see the solar granulation?
Thank you
Tico

I can see it very clearly in a 100mm apo, but struggled with a 63mm Telementor on the same day. I could not get my 72mm to focus with the Herschel wedge, so couldn't check this but I suspect the answer is somewhere a little below 100mm.

You will likely see mottling on the surface in smaller scopes in good days, but actually reliably seeing granulation cells I would say 100mm in a decent apo or long focal length achro.

Others may disagree 😀😀.

[tico]

Thank you Stu for your kind response, you think, that a 100mm or 120mm achro, F5 or F6, the typical Synta models, short achromatic refractors, could allow to see the solar granulation or should they inexcusably be APO?

[Stu]

38 minutes ago, tico said:

Thank you Stu for your kind response, you think, that a 100mm or 120mm achro, F5 or F6, the typical Synta models, short achromatic refractors, could allow to see the solar granulation or should they inexcusably be APO?

Anything is possible Tico, but the problem with the fast achros is that they often suffer from spherical aberration which makes sharp, high powered views difficult to achieve. Chromatic aberration can be filtered out, but SA cannot be overcome easily.

It doesn't need to be an apo necessarily, I would suspect something like a good Tal 100RS or a 102mm f11 achro would do a similar job for alot less money.

[laudropb]

I have seen it using a Sky Watcher ST 102, so it does not need to be an Apo. As Stu has pointed out on a previous report on this subject it requires patience. Quite often the granulation comes into view only during periods of excellent seeing and you have to wait for these to occur. I have had some success with the old trick of gently tapping the tube creating a little movement as the eye often picks up more detail then.

Edited June 25, 2019 by laudropb

[tico]

For visual observation of Granulation is best the Baader film or the Wedge Hershell ?

Thanks

Tico.

[Paul73]

Definitely the wedge.

[Stu]

Yep, wedge for sure