Comparison between G band and K-line filters
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Comparison between G band and K-line filters
Dear All,
Here is a comparison between a G band filter (430 nm FWHM 2 nm) and a K-line filter (396 nm FWHM 10 nm). The seeing conditions were about the same for both images. The processing is exactly the same.
On the overall, the K-line and the G band images look about the same. The contrasts of the solar granulation and of the facular regions are similar.
The main difference is the slightly lower resolution of the K-line image due to the shorter wavelength (seeing gets worse with shorter wavelength).
With the 150 mm aperture, the result with a 430 nm FWHM 10nm is similar to the result with the 430 nm FWHM 2 nm. This is not the case with larger apertures. The smaller FWHM increases the contrast of intergranular bright spots.
In optimal seeing conditions, the K-line filter takes the lead thanks to the slighly larger resolution due to shorter wavelength (= reduced diffraction).
All in all, this makes the G-band filter an interesting alternative to the K-line filter.
Best regards
Here is a comparison between a G band filter (430 nm FWHM 2 nm) and a K-line filter (396 nm FWHM 10 nm). The seeing conditions were about the same for both images. The processing is exactly the same.
On the overall, the K-line and the G band images look about the same. The contrasts of the solar granulation and of the facular regions are similar.
The main difference is the slightly lower resolution of the K-line image due to the shorter wavelength (seeing gets worse with shorter wavelength).
With the 150 mm aperture, the result with a 430 nm FWHM 10nm is similar to the result with the 430 nm FWHM 2 nm. This is not the case with larger apertures. The smaller FWHM increases the contrast of intergranular bright spots.
In optimal seeing conditions, the K-line filter takes the lead thanks to the slighly larger resolution due to shorter wavelength (= reduced diffraction).
All in all, this makes the G-band filter an interesting alternative to the K-line filter.
Best regards
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Re: Comparison between G band and K-line filters
Great images, Christian. I take it that the G-band is picking up both calcium and iron lines, or is it just calcium in the 2nm bandpass?
David
David
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Re: Comparison between G band and K-line filters
Well done, Christian! Very illustrative for imagers.
Have you inaged this group in a Ca II K line?
Valery
Have you inaged this group in a Ca II K line?
Valery
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Re: Comparison between G band and K-line filters
And, one question, Christian, if I may.
How do you process the images that near limb ares are same clean and detailed as the ares far from the limb.
I believe we all have the largest problems processing the near limb areas.
Thanks,
Valery
How do you process the images that near limb ares are same clean and detailed as the ares far from the limb.
I believe we all have the largest problems processing the near limb areas.
Thanks,
Valery
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Re: Comparison between G band and K-line filters
These are great
I agree with Valery, how do you get your limb shots so good
Is that a Baader K line filter? or a Lunt CaK filter?
Alexandra
I agree with Valery, how do you get your limb shots so good
Is that a Baader K line filter? or a Lunt CaK filter?
Alexandra
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Re: Comparison between G band and K-line filters
Outstanding comparison images Christian, well done, very informative
Pedro Re'
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Re: Comparison between G band and K-line filters
Superb comparison Christian
Brian
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Cambray, ON Canada
Photos: https://www.flickr.com/photos/185395281@N08/albums
10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
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Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
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Re: Comparison between G band and K-line filters
Good, well processed images ....
There's no calcium around 430nm....
I do think the K line filter brings out a bit more detail in the outlying plage areas
There's no calcium around 430nm....
I do think the K line filter brings out a bit more detail in the outlying plage areas
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Re: Comparison between G band and K-line filters
Good comparison thanks!
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Re: Comparison between G band and K-line filters
Thanks to all !
David : the G band is one of the lines named by Fraunhaufer. It is a group of CH lines with a FWHM of about 1 nm. The Ca II lines are farther to the near UV.
Valery : I did not taken any Ca K image of this group. In fact, I was comparing the Baader K-line, the Edmund Optic 430 nm FWHM 10nm, and the Andover 430 nm FWHM 2 nm.
BTW, the images were very pleasing visually with the G band filter, with a nice blue color and a lot of contrast in the granulation. The continuum gave less contrast. as for the K-line, It was far too blue for me.
As for the processing, there is nothing special. I just apply an unsharp mask filter over the whole image (k= 8, sigma = 1.4 pixel).
Alexandra : yes, this is the Baader K-line filter.
Ken : yes, there is a bit of more detail and contrast in the plage area with the K line. BTW, I really enjoyed your book. It is very well done !
David : the G band is one of the lines named by Fraunhaufer. It is a group of CH lines with a FWHM of about 1 nm. The Ca II lines are farther to the near UV.
Valery : I did not taken any Ca K image of this group. In fact, I was comparing the Baader K-line, the Edmund Optic 430 nm FWHM 10nm, and the Andover 430 nm FWHM 2 nm.
BTW, the images were very pleasing visually with the G band filter, with a nice blue color and a lot of contrast in the granulation. The continuum gave less contrast. as for the K-line, It was far too blue for me.
As for the processing, there is nothing special. I just apply an unsharp mask filter over the whole image (k= 8, sigma = 1.4 pixel).
Alexandra : yes, this is the Baader K-line filter.
Ken : yes, there is a bit of more detail and contrast in the plage area with the K line. BTW, I really enjoyed your book. It is very well done !
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
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Re: Comparison between G band and K-line filters
Hi Christian,
Thanks for sharing your findings. An eye opener for me.
Alfred
Thanks for sharing your findings. An eye opener for me.
Alfred