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

[yltansg]

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:



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:



and the same AR in CAK:



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

[Valery]

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

[p_zetner]

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

[Valery]

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

[LTHB]

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.

[DeepSolar64]

Very nice in both wavelengths.

[krakatoa1883]

Great H-alpha detail, may be a little too dark, may I suggest a brighter version ?

[marktownley]

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

[yltansg]

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


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

[yltansg]

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

[yltansg]

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

[yltansg]

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

[GreatAttractor]

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

[Montana]

The Halpha is really quite superb well done Alfred, this is miles better than I have ever achieved 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

[yltansg]

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:



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


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

[yltansg]

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

Alfred

[yltansg]

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

[marktownley]

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.

Mark

[yltansg]

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:



I hope I have looked at the right figure.

Alfred

[marktownley]

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?

[yltansg]

75%


70%


Image from stacking 500 frames:



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

Alfred

[marktownley]

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.

[yltansg]

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

[Montana]

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

[marktownley]

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.

[Carbon60]

This is certainly great information. Thanks for the discussion, guys.

Stu.

[yltansg]

Filip (GreatAttractor) processed another raw file, different from the image posted previously but taken on the same day 21 May (from stacking 500 frames) with ImPPG to produce this image (500frames - 70%, Q117)):
At 100% Q was 123



Subsequently, using the same ImPPG processing settings to process a 1000 frame, 1500 frame and 2500 frame image:

1000-frame stacking (63%, Q115)


1500-frame stacking (58%, Q114)


and finally 2500-frame stacking (52%, Q113)


All these images look about the same to me. There is no improvements in terms of details and also no significant blurring because of more frame stacking. Please give me your views. Next I will explore doing more stretching in ImPPG on the images with more frames to see if I can get more details out of them.

With Filip's permission I have attached his XML file for those who are keen to know.

Alfred

[krakatoa1883]

Alfred, can you share the raw ?

[yltansg]

Hi Raf,

Here they are:

092201 1000c1exp057.png (2.89 MiB) Viewed 839 times

092201 1500c1exp057.png (2.86 MiB) Viewed 839 times

[yltansg]

Here is the raw for the 500 frame-stack

092201 500c1exp057.png (2.97 MiB) Viewed 838 times

[solarGain]

Alfred, there is a lot going on here.
John

[dhkaiser]

h-alpha shot with good resolution!

[krakatoa1883]

Unfortunately I could not do anything better with your raws than GreatAttractor already did. However at that image scale I think you need a really excellent seeing to obtain good images. Why don't use a stronger reducer ?

[yltansg]

Thanks John and Dan for your kind words.

Krakatoa, Thanks for trying. For now, I don't think the solution is better image post processing.

I will be trying different configurations (with different CAK filters) to see what is the best I can get out of the C11 + ARIES D-ERF. Will post my findings.

Alfred