Planetary imaging - improvement tips please!

[Mr niall]

Hey all

I’ve been having fun imaging Jupiter and Saturn recently, but I’ve got to the point where my image quality seems to have hit a plateau. 
 

I’ve included my most recent Jupiter and Saturn for reference - I think the biggest things I would like to improve are;

1) Sharpness (although I am aware atmospheric conditions may play a part)

2) They seem “thin” - as in… lacking in depth, it feels like they go mottoes or pixelated very quickly when processing (if you see what I mean)

I haven’t managed to get a really defined Cassini division yet and that’s my next target.

Equipment - Skymax 127 on AZ GTI

Svbony 305pro (Sony imx290 2.9um pixels) shot at F12.5

Sharpcap for capture - around 25m/s 50% gain for Jupiter and around 70% for Saturn. Colourspace is RGB24 (tried raw8 and raw12 but seems really pixelated). 3000 frames, 640x480.

Processed using Autostakkert and Registax, best 20% kept.

[vlaiv]

14 minutes ago, Mr niall said:

Equipment - Skymax 127 on AZ GTI

Svbony 305pro (Sony imx290 2.9um pixels) shot at F12.5

This part is fine

14 minutes ago, Mr niall said:

Sharpcap for capture - around 25m/s 50% gain for Jupiter and around 70% for Saturn. Colourspace is RGB24 (tried raw8 and raw12 but seems really pixelated). 3000 frames, 640x480.

This part - I'm not really sure.

What does 25m/s mean? If you mean that you used 25ms exposures - than that is definitively not fine. You want your exposures to be around 5-6ms. Don't look at histogram values - don't try to get them to certain percentage of maximum. That is not important. Important bit is freezing the seeing and you can only do that with short exposures.

Gain needs to be set as to minimize the read noise. Do you have any graphs - Gain vs read noise or similar for this camera? If not - then use high gain settings like 90% or so. Usually read noise goes down when you up the gain.

Use Raw8 color space and save movie as ser, and then later select RGGB debayer in AS!3.

3000 frames is very low frame count - you want something like x10 or more. Try to get high FPS if you can (USB 3.0 connection, SSD, and fast capture mode / turbo USB - what ever you have available in SharpCap). 640x480 ROI is good - you can even go smaller if that will help with FPS

Image for 4 minutes or so.

Stack only 5-10% of the best frames.

[Mr niall]

On 05/10/2021 at 21:15, vlaiv said:

This part is fine

This part - I'm not really sure.

What does 25m/s mean? If you mean that you used 25ms exposures - than that is definitively not fine. You want your exposures to be around 5-6ms. Don't look at histogram values - don't try to get them to certain percentage of maximum. That is not important. Important bit is freezing the seeing and you can only do that with short exposures.

Gain needs to be set as to minimize the read noise. Do you have any graphs - Gain vs read noise or similar for this camera? If not - then use high gain settings like 90% or so. Usually read noise goes down when you up the gain.

Use Raw8 color space and save movie as ser, and then later select RGGB debayer in AS!3.

3000 frames is very low frame count - you want something like x10 or more. Try to get high FPS if you can (USB 3.0 connection, SSD, and fast capture mode / turbo USB - what ever you have available in SharpCap). 640x480 ROI is good - you can even go smaller if that will help with FPS

Image for 4 minutes or so.

Stack only 5-10% of the best frames.

Thanks Vlaiv that’s a great help,

the only reference I can find for gain:read noise is 1:15.37.

And this pinched from cloudy nights;

Gain Value e / ADU Read Noise (e) Full Well (e) Relative Gain Rel. Gain (db) Plage dynamique (arrêts)

1 53,51718504 15,41294929 13700,39937 1 0 8

1 53,49988682 15,4079674 13695,97103 1,000323332 0,002807972 8

1 53,2706365 15,34194331 13637,28294 1,004628226 0,040107519 8

1 53,24938755 15,33582362 13631,84321 1,005029119 0,043572895 8

2 26,30033128 7,574495409 6732,884808 2,034848325 6,170640859 8

3 18,00270287 5,184778427 4608,691935 2,972730563 9,463110964 8

3 17,99257615 5,181861932 4606,099495 2,974403698 9,467998248 8

5 10,687864 3,078104832 2736,093184 5,007285369 13,99204686 8

6 8,996134626 2,590886772 2303,010464 5,948908867 15,48874632 8

7 7,585126959 2,184516564 1941,792502 7,055542423 16,97060815 8

9 5,919660762 1,7048623 1515,433155 9,0405831 19,12392885 8

12 4,491903321 1,293668157 1149,92725 11,91414445 21,52125723 8

15 3,534253406 1,017864981 904,768872 15,14243007 23,60391153 8

19 2,786607465 0,80254295 713,3715112 19,20513948 25,66834931 8

25 2.087201755 0,601114105 534,3236493 25,6406382 28,17857661 8

29 1,840842201 0,530162554 471,2556033 29,07211983 29,269534 8

190 1,742364914 0,501801095 446,0454179 30,71525639 29,7470829 8

200 1,766410019 0,508726085 452,2009648 30,29714759 29,62803485 8

400 1,767016897 0,508900866 452,3563255 30,28674211 29,62505119 8

890 1,76654012 0,508763555 452,2342707 30,29491628 29,62739513 8

900 1,766020558 0,508613921 452,101263 30,30382902 29,62995014 8

To be honest I’m following a guide that’s a few years old now and then copying the workflow of someone who has used this camera and posted their results. I was struggling to get my head around the relationship between frame rate and gain, but I will definitely follow your advice and push the frame rate down to 5/6 ms.

I’ll go back to Raw 8 and use SER too.

I will report back!

Many thanks!

[vlaiv]

1 minute ago, Mr niall said:

To be honest I’m following a guide that’s a few years old now and then copying the workflow of someone who has used this camera and posted their results. I was struggling to get my head around the relationship between frame rate and gain, but I will definitely follow your advice and push the frame rate down to 5/6 ms.

You want this line:

190 1,742364914 0,501801095 446,0454179 30,71525639 29,7470829 8

This gives ~0.5e of read noise - lowest. It is gain of 190 or "relative gain" of 30.71 (whatever that means)

There is no relationship between gain and frame rate. You want lowest read noise and that is to some extent controlled by gain. Just simply select gain that provides lowest read noise.

Exposure length is related to frame rate in certain way.

You want your exposure length to be such that it freezes the seeing. That is in most cases around 5-6 ms. In very good seeing it can be as high as 10ms. You'll recognize such seeing as image being quite steady on preview - no jumping around or fast blurring of features.

Exposure length limits max fps that you can achieve and relationship is as follows 1000/exposure = max fps.

If you set you exposure to say 5ms - max FPS that is theoretically possible is 200FPS - you simply can't have more than that as there is only limited amount of time in one second .

Real FPS will also depend on your camera and computer USB connection and also how fast computer can save those frames. Choosing smaller ROI will help there.

[Mr niall]

On 05/10/2021 at 22:12, vlaiv said:

You want this line:

190 1,742364914 0,501801095 446,0454179 30,71525639 29,7470829 8

This gives ~0.5e of read noise - lowest. It is gain of 190 or "relative gain" of 30.71 (whatever that means)

There is no relationship between gain and frame rate. You want lowest read noise and that is to some extent controlled by gain. Just simply select gain that provides lowest read noise.

Exposure length is related to frame rate in certain way.

You want your exposure length to be such that it freezes the seeing. That is in most cases around 5-6 ms. In very good seeing it can be as high as 10ms. You'll recognize such seeing as image being quite steady on preview - no jumping around or fast blurring of features.

Exposure length limits max fps that you can achieve and relationship is as follows 1000/exposure = max fps.

If you set you exposure to say 5ms - max FPS that is theoretically possible is 200FPS - you simply can't have more than that as there is only limited amount of time in one second .

Real FPS will also depend on your camera and computer USB connection and also how fast computer can save those frames. Choosing smaller ROI will help there.

Amazing - thanks again