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Old 19-04-2019, 04:40 PM
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Merlin66 (Ken)
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AR 2738 19 April Ha wings and CaK

A few images....
The colorized CaK images show the shape of the major AR 2738 spot (and the following AR2739 group) BUT I'm not convinced that it shows the Wilson effect! It appears to me that the trailing penumbra (towards the sun's centre is actually wider than the section close to the edge - the opposite of the Wilson effect.
The next image in the Blue wing shows once again the extent of the spot - you decide: which penumbral section is wider?
The last image in the red wing shows the typical Ha filigree and magnetic swirls..Oh...and the local prom.

ED80/ SM60, PST Mod x2.5PM, ASI 174

(It's good to see the PST DS working well and suppressing the Photospheric sharp edge - just the blended spiculation)
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Last edited by Merlin66; 19-04-2019 at 05:02 PM.
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Old 19-04-2019, 11:36 PM
Saturnine (Jeff)
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Great images once again, has been fun following Ar 2738 on its journey around Sol.
I need to brush up on my solar terminologies but I presume that the Wilson Affect that you mention is caused by the cooler sunspots being depressed into the photosphere, so that when close to the limb the leading edge of the penumbra is tilted slightly more to our line of sight thus appearing wider. Assuming that the spot has a reasonably symmetrical shape.
It would seem that the spot is an oval shape now with the long axis pointing to our line of sight, which may explain why the trailing side of the penumbra looks wider.
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Old 20-04-2019, 08:19 AM
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Outcast (Carlton)
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Hi Ken,

Nice pics & outstanding details as always.

Dumb question but, can you explain blue & red wing please? Does this relate to etalon tuning & which end of the narrow Ha band one is viewing?

Cheers

Carlton
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Old 20-04-2019, 09:00 AM
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Merlin66 (Ken)
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Carlton,
The H alpha solar absorption line when you look at the profile, is like a deep valley with wider top section. The width of the line is >2A. Beyond the wider section we move from H alpha into the solar continuum.
Simplistically, if our H alpha filter has a bandwidth of <1A then we can position it at the deepest (central section) or out in the wider sections....
The wider top sections are the "wings" of the Ha line - the blue wing towards the blue, and red the opposite.

When we observe at the Ha core (6262.8 A CWL (central wavelength)) we are looking at a region of the Chromosphere around 1500 Km above the "White light" Photosphere. As we move our filter (tuning) out into the "wings" we start to see detail lower in the Chromosphere - 200 - 300 Km above the Photosphere.

Besides the possible Doppler shift (which changes the appearance of some of the filaments - which also requires working in the wings), the wings also allow us to better see and record things like Ellerman Bombs and flares.
Hope this helps.
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Old 20-04-2019, 09:47 AM
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Outcast (Carlton)
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Thanks Ken,

That pretty much is what I thought (though perhaps not in those terms), essentially we are looking at the HA band within the context of the the overall light spectrum; ie: blue to red, and then taking that into the subset of the HA bandwidth that we are viewing.

So, in terms of HA tuning via the etalon..., specifically in my case a pressure tuned unit, am I correct in assuming that with my tuner wound out (lower air pressure), I achieve longer wavelengths, relatively speaking & am thus at the blue wing whereas when wound in (higher air pressure) I achieve shorter wavelengths & am thus at the red wing? Somewhere in the central point of my pressure tuner will be the mid point of the HA band that I am observing.. does that sound correct in basic terms or, am I completely off track?

I am hopeful that by understanding how this tuning works, relative to the spectrum & combined with the information you provide in your posts, I can better understand the tuning of my scope & begin to better understand what features will show best at which tuning points & with time & experience, everything in between.

Cheers

Carlton

Quote:
Originally Posted by Merlin66 View Post
Carlton,
The H alpha solar absorption line when you look at the profile, is like a deep valley with wider top section. The width of the line is >2A. Beyond the wider section we move from H alpha into the solar continuum.
Simplistically, if our H alpha filter has a bandwidth of <1A then we can position it at the deepest (central section) or out in the wider sections....
The wider top sections are the "wings" of the Ha line - the blue wing towards the blue, and red the opposite.

When we observe at the Ha core (6262.8 A CWL (central wavelength)) we are looking at a region of the Chromosphere around 1500 Km above the "White light" Photosphere. As we move our filter (tuning) out into the "wings" we start to see detail lower in the Chromosphere - 200 - 300 Km above the Photosphere.

Besides the possible Doppler shift (which changes the appearance of some of the filaments - which also requires working in the wings), the wings also allow us to better see and record things like Ellerman Bombs and flares.
Hope this helps.
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Old 20-04-2019, 10:20 AM
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Merlin66 (Ken)
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Carlton,
Working in the core/ wings just takes some practise - to recognise the dominant features.

With a tilt etalon (External and PST) more tilt takes you towards the blue wing..
For the Lunt pressure system, higher pressure moves towards the red wing.
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