I keep getting this dotted pattern on my planetary images when i process them. Is it normal or am i doing something wrong?

[MKHACHFE]

Hello all you fine folk,

I have been doing some planetary AP this last year using my standard Orion XT8 and my ASI 120mm guide camera for regular AP.  I get decent enough results, especially considering Jupiter and Saturn are very low where i live and i have to image them over the roofs of other houses...so lots of atmospheric distortion.  I generally dont use a Barlow, although i have a x2 and 3x, mainly because its very difficult to get the target in sight (i use Sharpcap Pro) due to a multitude of issues ranging from stiction in my XT8 movement, inability to get RA finder aligned with my telescope view accurately enough...but i wont get into those now. 

I tend to capture 16bit mono SER files, generally at around 70fps. I usually end up with around 3000 usable frames that i put through PIPP, then Autostakkert, then either process in Registax or Astra Image (usually the former). 

Now, i know that i don't have as many frames as is recommended, but assuming that isn't the sole or main reason i get this type of pattern, is there anything else i'm doing wrong, or is this just par for the course with this type of planetary AP on this kind or setup?

I know that using a 3x Barlow is the ideal match for my XT8, using that calculation method i read about. Would there be a marked improvement in sharpness in my frames if i used it? Obviously the planet would be larger in size. 

 

I have attached an exaggerated image of my stack in Registax to show the pattern im talking about, and also what my original Autostakkert output looks like with no processing.  The 16bit Tif file is in the link below and i have inserted a 200% jpg version as well just for quick viewing

 

Thanks very much for reading this rambling mess and i hope everyone has a wonderful bank holiday weekend. 

 

Cheers

 23_30_45_pipp_test_lapl5_ap85.tif

Edited August 26, 2022 by MKHACHFE
added additional image and forgot to say thanks!

[Ags]

That is from over-sharpening I think, sharpening has the downside of sharpening the noise too.

[MKHACHFE]

4 minutes ago, Ags said:

That is from over-sharpening I think, sharpening has the downside of sharpening the noise too.

Oh yeah, sure, i know that, i was just really asking if there is anything i can do prior to processing to reduce this pattern. Would capturing more frames help (i know Jupiter has a three minute ish max length of capture due to its rotation, im not advanced enough to use WinJupos), or using my Barlows, or is just a matter of processing a little at a time, using low values then saving that, and editing again etc...

 

Thanks for the QUICK reply AGS!

[vlaiv]

18 minutes ago, MKHACHFE said:

The 16bit Tif file is in the link below and i have inserted a 200% jpg version as well just for quick viewing

I'm a bit confused with what you've written above and your data.

First, here is what can be teased out from that tif:

A bit noisy, but decent amount of detail.

But here is the problem. You say you use XT8 and ASI120 without any barlow.

That is 1200mm of focal length at 3.75um pixel size. Sampling rate is therefore ~0.645"/px

Jupiter is about 45-50 arc seconds in diameter at opposition (depends on year), but let's take 50".

With above sampling rate and 50" - max size of Jupiter in pixels that you can record is about 77px. I've measured diameter of Jupiter in your image above to be around 170px give or take.

My guess is that you drizzled your data x3 in AS!3. You already don't have good frame count to combat noise and you on top of that drizzled your data which severely reduces SNR and does not improve detail.

When you start denoising, and in particular applying deconvolution to such noisy over sampled data - you get bunch of ripples around noisy dots. That is what your large image represents.

Btw - look at how nice image looks at 50% size of that tiff:

I know it is small, but it is sharp and virtually noise free.

[MKHACHFE]

3 hours ago, vlaiv said:

I'm a bit confused with what you've written above and your data.

First, here is what can be teased out from that tif:

A bit noisy, but decent amount of detail.

But here is the problem. You say you use XT8 and ASI120 without any barlow.

That is 1200mm of focal length at 3.75um pixel size. Sampling rate is therefore ~0.645"/px

Jupiter is about 45-50 arc seconds in diameter at opposition (depends on year), but let's take 50".

With above sampling rate and 50" - max size of Jupiter in pixels that you can record is about 77px. I've measured diameter of Jupiter in your image above to be around 170px give or take.

My guess is that you drizzled your data x3 in AS!3. You already don't have good frame count to combat noise and you on top of that drizzled your data which severely reduces SNR and does not improve detail.

When you start denoising, and in particular applying deconvolution to such noisy over sampled data - you get bunch of ripples around noisy dots. That is what your large image represents.

Btw - look at how nice image looks at 50% size of that tiff:

I know it is small, but it is sharp and virtually noise free.

So, my suspicions were correct. Not using either of my Barlows has not helped. 

Yes, you are correct, i x3 drizzled i AS!3. 

OK...so my next tasks are to smooth my XT8 movement, properly align my finder to my eyepiece view and try again with my 2x and 3x barlows. 

 

Thanks for your advice and kind words on how it looks nice at 50% size.  Im not being sarcastic by the way, but that did make me chuckle because when i started doing 3d animation many, many moons ago, we would render at 640x480 or at most 800x600...everything was so easy to get away with at those resolutions 😁 But now! I have to render 4 and 8k which is BRUTAL with regards to details and mistakes. 😩

Everything looks good small. 

 

Cheers, have a great weekend mate

[vlaiv]

9 hours ago, MKHACHFE said:

OK...so my next tasks are to smooth my XT8 movement, properly align my finder to my eyepiece view and try again with my 2x and 3x barlows. 

You should aim for F/15, so x2.5 barlow would be ideal.

Barlow magnification changes as you change sensor to barlow element distance. This can help you get x2.5 from either of two barlows that you own. For x2 you need to increase sensor barlow distance and for x3 - you need to reduce it.

In any case - you can dial in x2.5 in daytime if you record distant object and do some measurements and calculations. Find object with feature that is easily measured for size in pixels - like tall building, church tower, bridge.

Shoot it without barlow and measure size in pixels. Now use barlow and adjust distance (using spacers, adjustable extension or pulling camera nose piece in/out of the barlow itself) and record/measure again until you get image that is x2.5 as large (x2.5 more pixels measured in feature).

That is your target setup.

[MKHACHFE]

16 hours ago, vlaiv said:

You should aim for F/15, so x2.5 barlow would be ideal.

Barlow magnification changes as you change sensor to barlow element distance. This can help you get x2.5 from either of two barlows that you own. For x2 you need to increase sensor barlow distance and for x3 - you need to reduce it.

In any case - you can dial in x2.5 in daytime if you record distant object and do some measurements and calculations. Find object with feature that is easily measured for size in pixels - like tall building, church tower, bridge.

Shoot it without barlow and measure size in pixels. Now use barlow and adjust distance (using spacers, adjustable extension or pulling camera nose piece in/out of the barlow itself) and record/measure again until you get image that is x2.5 as large (x2.5 more pixels measured in feature).

That is your target setup.

Thank you very much for the advice.

Cheers