21May - C11 HA/CAK Close-ups - Images added 23 May 20

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21May - C11 HA/CAK Close-ups - Images added 23 May 20

Post by yltansg » Thu May 21, 2020 2:25 pm

21May20. The sky was clouded out in the earlier part of the morning and focus was drifting throughout the session from 9am to 11 am local time.
The setup is shown below:

Image

I did both CAK and then HA imaging. The HA optical train has been optimised. I am building up my "database" for CAK imaging to find optimal configuration (in terms of mask and filter). The setup for the imaging sessions are:
ARIES D-ERF on C11 with Daystar HA Quark (with x0.8 reducer) for HA and Lunt CAK B21200 module + PST Yellow filter (with x2 barlow) for CAK imaging with a 220mm mask.

The object is the AR in the northern hemisphere. First the HA image:

Image

and the same AR in CAK:

Image

Please do a right-click to see the images in full resolution.

For both images, I only performed processing in ImPPG and added contrast and levels in photoshop. Both images can be further improved, if only I know how :)

Alfred
Last edited by yltansg on Sat May 23, 2020 11:40 am, edited 1 time in total.



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Re: 21May - C11 HA/CAK Close-ups

Post by Valery » Thu May 21, 2020 4:06 pm

Hi Alfred,

The H-a image is really good. Not perfect, but really good in such conditions.

BTW Can you, please, post a PNG 16 bit raw files of both images or send them to my e-mail?


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Re: 21May - C11 HA/CAK Close-ups

Post by p_zetner » Thu May 21, 2020 4:30 pm

Beautiful H alpha shot, Alfred.

The CaK shot is soft, though. Is there not a problem with spherochromatism in the SCT at 393nm?

All the best.
Peter



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Re: 21May - C11 HA/CAK Close-ups

Post by Valery » Thu May 21, 2020 4:44 pm

p_zetner wrote:
Thu May 21, 2020 4:30 pm
Beautiful H alpha shot, Alfred.

The CaK shot is soft, though. Is there not a problem with spherochromatism in the SCT at 393nm?

All the best.
Peter
Not with such an aperture stop. At 220mm this scope is diffraction limited. No gain in sharpness with a smaller aperture.
However I would advice to use Powermate 2.5x and not a simple Barlow lens which is poorly corrected at 393nm.

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Re: 21May - C11 HA/CAK Close-ups

Post by LTHB » Thu May 21, 2020 5:35 pm

Nice h-alpha shot with good resolution!

As for CaK: Another way to solve the barlow problem (although a bit more expensive than buying a Powermate) would be to change the camera to an ASI290, which has a pixel size almost exactly half of that of the ASI174 (and is less noisy) and drop the barlow/powermate.



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Re: 21May - C11 HA/CAK Close-ups

Post by DeepSolar64 » Thu May 21, 2020 5:44 pm

Very nice in both wavelengths.


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Re: 21May - C11 HA/CAK Close-ups

Post by krakatoa1883 » Thu May 21, 2020 5:58 pm

Great H-alpha detail, may be a little too dark, may I suggest a brighter version ?
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100522 2000H2i4crmklvl_bright.jpg
100522 2000H2i4crmklvl_bright.jpg (211.27 KiB) Viewed 324 times


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Re: 21May - C11 HA/CAK Close-ups

Post by marktownley » Thu May 21, 2020 7:41 pm

Nice results Alfred, was the Ha at full aperture or 220mm?


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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 3:27 am

Valery wrote:
Thu May 21, 2020 4:06 pm
Hi Alfred,

The H-a image is really good. Not perfect, but really good in such conditions.

BTW Can you, please, post a PNG 16 bit raw files of both images or send them to my e-mail?


Valery
Thanks Valery for your comments. I have sent you the raw files. I have also posted them here for others who may be interested to have a go at them and post their result here:

2000 frame-stack of 8-bit raw file for the HA image
Image

2800 frame-stack of 8-bit raw file for the CAK image:

Image

For the CAK image, I have attached a different file which has better Signal-to-Noise ratio compared to the one I posted earlier.

Unfortunately, the sky was clouded out this morning. Hope to catch some image this weekend.

Alfred
Last edited by yltansg on Fri May 22, 2020 8:38 am, edited 2 times in total.



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 3:29 am

Valery wrote:
Thu May 21, 2020 4:44 pm
p_zetner wrote:
Thu May 21, 2020 4:30 pm
Beautiful H alpha shot, Alfred.

The CaK shot is soft, though. Is there not a problem with spherochromatism in the SCT at 393nm?

All the best.
Peter
Not with such an aperture stop. At 220mm this scope is diffraction limited. No gain in sharpness with a smaller aperture.
However I would advice to use Powermate 2.5x and not a simple Barlow lens which is poorly corrected at 393nm.

Valery
It will be in the list of things that I would do differently when it is clear for imaging. Thanks.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 3:31 am

krakatoa1883 wrote:
Thu May 21, 2020 5:58 pm
Great H-alpha detail, may be a little too dark, may I suggest a brighter version ?
Hi Raf,

That is a great suggestion. Your brighter version looks much "clearer" Thanks.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 3:34 am

marktownley wrote:
Thu May 21, 2020 7:41 pm
Nice results Alfred, was the Ha at full aperture or 220mm?
Hi Mark,

The HA image was done at full aperture and the CAK images at 220mm, LUNT CAK module + PST yellow filter. I have made a number of CAK recordings and finding time to process them. Should find some more good CAK images.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by GreatAttractor » Fri May 22, 2020 6:43 am

Alfred,
I may be doing something wrong, but when trying to download, I'm getting 8-bit JPG images.


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Re: 21May - C11 HA/CAK Close-ups

Post by Montana » Fri May 22, 2020 7:56 am

The Halpha is really quite superb :bow :hamster: well done Alfred, this is miles better than I have ever achieved :bow but please do not buy a 2.5x Powermate from TeleVue as you will be wasting your money, it has the most terrible reflection in the centre and does not work at all on a C11. It is however a great C11 collimation tool ;)

Alexandra



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 8:25 am

Dear Alexandra,

Thank you very much for your advice. Yes, I remembered your pain.

I am still working on the CAK capture. The images tend to be "cloudy" and not focused. Even with a 4000frame-stacking (such be good signal-to-noise ratio), the result is still poor, as you can see below:

Image

The quality curve of this video recording of this 7048 frames was good:
Image

The video recording was done at 88 FPS (avg.), Shutter=11.12ms and Gain=330 (82%) on FireCapture. I am looking into different aspects to see how to improve the image.

Comments and suggestions are greatly appreciated.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 8:30 am

LTHB wrote:
Thu May 21, 2020 5:35 pm
Nice h-alpha shot with good resolution!

As for CaK: Another way to solve the barlow problem (although a bit more expensive than buying a Powermate) would be to change the camera to an ASI290, which has a pixel size almost exactly half of that of the ASI174 (and is less noisy) and drop the barlow/powermate.
Thanks for the suggestion. The ASI290 is on my wish list :lol:

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 8:40 am

GreatAttractor wrote:
Fri May 22, 2020 6:43 am
Alfred,
I may be doing something wrong, but when trying to download, I'm getting 8-bit JPG images.
Dear Filip,

Thank you for alerting me that the files get converted into jpeg files. I have PMed you and attached the TIFF raw files. Please let me know on PM if they are delivered to you as attachments.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by marktownley » Fri May 22, 2020 9:25 am

Hi Alfred.

The screen grabs are useful. One question; in the image window in AS3 what is the quality value for the best single frame? It will tell you this when you have analysed the avi file but before you stack it. I opened the unprocessed image and it gives me a value of 27.1 which is very low.

I think your quality value of 4 is a mile off, depending on how much higher the best frame is than 27.1 I might go for a 5, but I think a 6 is more realistic . Don't forget imaging where the seeing is not supporting the aperture this has the effect of gaussian blur on the image so finer details are lost. The stacking software needs to look for larger features to stack than if the data was good to start. I always stack at the 75% value, so, with your 7k frames I would probably stack 250, but that may well not work as the gain was up at 82%

The cloudiness as others have noticed is spherical aberration inherent with a SCT system. Stopping down will reduce it but will not remove it. The more you stop down the more the strehl is reduced by the increasing ratio of secondary to primary ratio, and so contrast is lowered further. There will be a goldilocks zone with stopping down as Valery notes, however the seeing needs to support this. Remember, the image you got above at 295mm in Ha, you would have got the same sharpness at 178mm in Cak.

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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 9:42 am

marktownley wrote:
Fri May 22, 2020 9:25 am
Hi Alfred.

The screen grabs are useful. One question; in the image window in AS3 what is the quality value for the best single frame? It will tell you this when you have analysed the avi file but before you stack it. I opened the unprocessed image and it gives me a value of 27.1 which is very low.

Mark
Thanks Mark for taking time to look at it. the quality of the best single frame (Frame 3709), before stacking is Q 100%, as shown below:

Image

I hope I have looked at the right figure.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by marktownley » Fri May 22, 2020 9:49 am

So, the Q value of the best frame is 154.4, which is considerably better than the final image value of 27.1. You're stacking the fine detail away by using so many frames. If you click on where the green line crosses the 75% what is the quality value there?


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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 10:34 am

75%
Image

70%
Image

Image from stacking 500 frames:

Image

I have stacked 500frames, 1000frames, 1500 frames, 2000frames and 4000 frames. Interesting results....

Alfred
Last edited by yltansg on Fri May 22, 2020 10:55 am, edited 1 time in total.



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Re: 21May - C11 HA/CAK Close-ups

Post by marktownley » Fri May 22, 2020 10:39 am

Even at 70% the Q value is 145 which is considerably higher than the Q value of 27 with 4000 stacked frames.

If you reopen the stacked images in AS3 as an image file (you will have to change the drop down so it looks for 'image files' instead of 'all supported video files') it will give you a quality value for your stacked image.


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Re: 21May - C11 HA/CAK Close-ups

Post by yltansg » Fri May 22, 2020 10:57 am

marktownley wrote:
Fri May 22, 2020 10:39 am
Even at 70% the Q value is 145 which is considerably higher than the Q value of 27 with 4000 stacked frames.

If you reopen the stacked images in AS3 as an image file (you will have to change the drop down so it looks for 'image files' instead of 'all supported video files') it will give you a quality value for your stacked image.
Thanks Mark for the education.

Alfred



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Re: 21May - C11 HA/CAK Close-ups

Post by Montana » Fri May 22, 2020 11:42 am

This is very interesting, I had no idea about this :)
Alexandra



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Re: 21May - C11 HA/CAK Close-ups

Post by marktownley » Fri May 22, 2020 12:49 pm

After analysis and before stacking ctrl click anywhere on the green quality line will put what the % value to stack in the first of the 4 boxes.


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