AR12671 and AR12672 from August 21 using EdgeHD11 WL

[LauraMS]

Hello,

it was a long time since my last posting because of holidays .. I did some imaging, but I'm somewhat stuck with data overflow ...

Anyway, here are some nice images from yesterday. There was a high cloud layer with low very transparency. In addition larger clouds witch made imaging - well - less pleasant. Anyway, I learned that this turned out to be excellent with regard to seeing because temperature (21°C) was well below normal temperatures at this time of the year with full sun (>28°C). This resulted in very good ground layer seeing, probably the best I ever had with my Edge 11. Only the jetstream was suboptimal (54.2m/s) but still, overall conditions weren't bad at all:

I had to rotate the camera to get it into the field of view considering the focal length used for imaging today (6975mm) using Televue 2.5x telecentric. Image scale with my Basler IMX174 camera (acA1920-155) was 0.17''/px. Imaging was done using Baader ASTF ND3.8, Airylab Seeing Monitor and GenikaAstro. Postprocessing using AS3 (1% stacked), IMPPG, XnView.

Full view (09:38 UT, Seeing min/ave/max = 0.47''/0.96''/1.40''), 12 bit acquisition for 20sec at 55fps using Baader 35nm Halpha filter with 18ms exposure time and gain 3800. This is a unusually long exposure time but it was needed to be able to work with low gain despite the high clouds. Nice side effect: 12 bit acquisition didn't come with a lower fps-value.

AR12671 2017-08-21 11-38-50 Halpha.jpg (212.85 KiB) Viewed 3469 times

Considering that the spot fills completely the full field of view of this scope/camera/barlow-configuration (whichis 240 x 150 Mm (Mega-meters)), and that it was almost at the center of the solar disk with now shortening due to perspective, this active region is huge ! For comparison: the circumference of the earth is 40 Mm and it's diameter 12.742 Mm. So from east to west, AR is more than six times around the earth at the equator ...

Detail view of the preceding spot of AR12671 using the SolarContinuum filter at 09:30 UT. Seeing was slightly better than before (min/ave/max = 0.29''/0.73''/1.25''), otherwise imaging parameters were the same :

AR12671 ps 2017-08-21 11-30-28 SolarContinuum.jpg (55.28 KiB) Viewed 3469 times

Because of the good seeing granulation was nicely visible in the raw video without any postprocessing (100 images of the original ser-file with no postprocessing but only adjustment of gamma and overall brightness can be found in the attachment of this post).

And here from the same acquisition some central spot detail:

AR12671 cs 2017-08-21-11-30-28 SolarContinuum.jpg (77.33 KiB) Viewed 3469 times

And finally, the follwing part of the spot from another acquistion at 09:31 UT (Seeing min/ave/max = 0.19''/0.45''/1.09''), otherwise imaging parameters were the same.

AR12671 fs 2017-08-21-11-31-22 SolarContinuum.jpg (76.75 KiB) Viewed 3469 times

Processing was a bit hard to better visualize the bright spots on the fibrills.

And then there was AR12672 which just appeared a day before at the eastern limb:

AR12672 2017-08-21 11-00-12 SolarContinuum.jpg (373.27 KiB) Viewed 3469 times

(09:00 UT, Seeing min/ave/max = 0.47''/0.98''/1.59'', 12 bit acquisition for 20sec at 50fps using SolarContinnum filter with 20ms exposure time and gain 7527). Camera was rotated by about 25°from previous imaging of AR12671)

Enjoy, Laura

[LauraMS]

Some more postprocessing making with the hope of extracting more detail from the 12 bit data:

Stacking 20% of 998 images:

AR12671 fs cs 2017-08-21-11-31-22 SolarContinuum p20-1.jpg (208.67 KiB) Viewed 3449 times

And here with more detail in the fibrils and light bridge at the expense of umbral detail:

AR12671 fs cs 2017-08-21-11-31-22 SolarContinuum p20-2.jpg (200.9 KiB) Viewed 3449 times

30% of the 998 images:

AR12671 fs cs 2017-08-21-11-31-22 SolarContinuum p30-1.jpg (239.73 KiB) Viewed 3449 times

And finally: 40% of 998 images:

AR12671 fs cs 2017-08-21-11-31-22 SolarContinuum p40-1.jpg (301.72 KiB) Viewed 3449 times

Btw., did you see the happy face spot

AR12671 fs cs 2017-08-21-11-31-22 SolarContinuum p30-1 HappyFace.jpg (572.48 KiB) Viewed 3449 times

Which one do you like best? I think stacking 30% appears to be a sweet "spot" in this case

Enjoy, Laura

[eroel]

Laura:
Super images, liked best the 3 last ones, but mostly the 40% one.
Regards,
Eric.

[bart1805]

Really, really beautiful!
Can you tell a bit more about the Gamma setting, did you use neutral?

[krakatoa1883]

Superb detail, I like very much these images, the 40% stack seems to me the best one.

Have you tried the K line filter by Baader ?

[LauraMS]

Thanks guys for your nice comments :-) Agreement seems to be 40% is best.

@bart: Yes, Bart, I did use neutral setting. The reason for doing so is the fact that gamma correction is performed after conversion of the electrical signal on the CCd chip by use of its analog digital converter (ADc). This means you loose information if you perform gamma correction during acquisition because it is done by software later. It may also be done within some cameras but still this would be done after ADC conversion. So you at least don't gain information.

@Raffaello: No, I didn't use the Baader K-Line filter. Mainly because it is hard to obtain good quality images at near UV wavelength. I am also wondering if a K-Line filter would be a good investment considering that a bit more expensive options (e.g. Quark K-Line) may give much better contrast. Do you have experience with it?

Best, Laura

[pedro]

Beautiful HR WL images Laura

[krakatoa1883]

@Raffaello: No, I didn't use the Baader K-Line filter. Mainly because it is hard to obtain good quality images at near UV wavelength. I am also wondering if a K-Line filter would be a good investment considering that a bit more expensive options (e.g. Quark K-Line) may give much better contrast. Do you have experience with it?

Yes, I like it very much as it significantly increases contrast on granulation and penumbrae. In this topic viewtopic.php?f=10&t=22564&p=207181#p207181 you can find a detailed comparison between Continuum and K filters. It requires a very fine seeing, however.

[Carbon60]

Super images, Laura. Lots of lovely details.

Stu.

[LauraMS]

Thanks for your kind comments, Pedro and Stu.

@Raffaello: thanks for hinting me at that thread. It's a bit lengthy. Which is good, but I will take my time to read it carefully ...

Best, Laura

[ffellah]

Fantastic images, Laura ! All of them....

Franco

[dvmak]

Great images, thanks for sharing!

[bart1805]

Thanks for your answer Laura! One more question. Did you choose to capture with Gain at 3800 because otherwise the exposure time would have been to long?

[LauraMS]

Thanks for encouraging me, Franco and Dmitri!

Bart, yes exposure time was quite long and I wanted to at least reduce it a bit. From experience I know that up tp about 4000 gain value not to much additional noise will be introduced. Usually I don't go much above that value.

Best, Laura

[bart1805]

Thanks again Laura! Very interesting to read what levels others use to capture.
And I learned from your post that I do have to compare 12 Bit to 8 Bit.
Happily waiting for your next beautiful images,
Bart.

[xn44]

[jp-brahic]

very nice shots Laura

JP

[LauraMS]

thanks, JP, xn44 and Bart