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5x rule? - Jupiter with 10, 14 and 16 in aperture

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#1 Jan_Fremerey

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Posted 20 January 2025 - 10:59 AM

A recent R-RGB re-evaluation of Jupiter data from 2012 December 12 taken with my 10" Newton and 5.2 µm ALccd5 camera at f/13 uncover image detail not seen on simultaneous 14" and 16" images by Christopher Go and Marco Guidi taken at the same time under "excellent" resp. "very good" seeing conditions.

 

 

ALPO-Eintrag.jpg

 

See in particular tiny double line above northern cloud band. I suspect too long focal adaptation and single frame exposure times in case of the larger telescopes.

 

CS Jan


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#2 vidrazor

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Posted 20 January 2025 - 11:11 AM

That appears to be over-sharpened, as you can see the boundary halation ringing artifacts of the sharpening process.



#3 andycknight

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Posted 20 January 2025 - 11:13 AM

What do you mean when you say 5x rule??

 

(Pixel size 5x smaller than focal ratio ??)

 

Confused because its 5.2um pixels @ F/13.

 

For 5.2um - I would be thinking F/20 (4x rule)

But I'm no expert so keen to know...

 

Nice image of Jupiter BTW - lots of detail smile.gif

 

Regards

 

Andy.



#4 Jan_Fremerey

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Posted 20 January 2025 - 11:24 AM

That appears to be over-sharpened, as you can see the boundary halation ringing artifacts of the sharpening process.

So you suspect the double line to be an artifact? The fact that a short section of the double line can be vaguely recognized on the 16” image speaks against this.



#5 Jan_Fremerey

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Posted 20 January 2025 - 11:41 AM

1. What do you mean when you say 5x rule??

2. Pixel size 5x smaller than focal ratio ??

3. For 5.2um - I would be thinking F/20 (4x rule)

4. Nice image of Jupiter BTW - lots of detail smile.gif

1. See Section 6.1 of this article.

2. Right.

3. I'm demonstrating that f/13 (2.5x) already works quite satisfying.

4. Thank you !

 

CS Jan


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#6 Borodog

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Posted 20 January 2025 - 11:53 AM

By R-RGB do you mean that you have used the red channel as a luminance layer, as in L-RGB processing as R-RGB?

 

If you really want to compare your image to Chris Go's, for example, put them on the same image scale. It's possible for a 10" under-sampled image in excellent seeing to equal (or exceed) an image from a larger aperture captured under lesser seeing, but to judge that you would want to compare the images at the same scale. 



#7 Borodog

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Posted 20 January 2025 - 12:01 PM

At Chris's image scale (click the thumbnail):

 

Comparison.jpg


Edited by Borodog, 20 January 2025 - 12:02 PM.


#8 Borodog

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Posted 20 January 2025 - 12:02 PM

At the OP's:

 

Comparison2.png


Edited by Borodog, 20 January 2025 - 12:03 PM.


#9 Jan_Fremerey

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Posted 20 January 2025 - 12:02 PM

1. By R-RGB do you mean that you have used the red channel as a luminance layer, as in L-RGB processing as R-RGB?

2. If you really want to compare your image to Chris Go's, for example, put them on the same image scale.

1. Yes.

2. I don't like blown-up images when they do not uncover additional image detail. I rather refer to clearly perceivable image detail.
 



#10 Jan_Fremerey

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Posted 20 January 2025 - 12:11 PM

At Chris's image scale

There is no addtional image detail on the enlarged image as compared to the original version. So its sort of "empty" enlargement.



#11 Borodog

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Posted 20 January 2025 - 12:21 PM

1. Yes.

2. I don't like blown-up images when they do not uncover additional image detail. I rather refer to clearly perceivable image detail.
 

 

You can just as easily reduce the larger image to the scale of the smaller one, as I've done above.

 

It is certainly the case that your high contrast processing has made certain details easier to see than Chris's processing. For example, certain details in the polar regions. Unlike many others I don't have anything in particular against high contrast planetary images and indeed I quite like them. I'm not a fan of using the red channel as a luminance channel, but it's all personal taste.

 

The difference between 2.5X sampling and 5X sampling is indeed relatively small, and can be wiped out entirely by seeing. But in exceptional seeing, there is no way I would trade 5X sampling for 2.5X sampling, and would indeed prefer up to 7X sampling, and there is no chance I would trade a 14" or 16" aperture for a 10" aperture.


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#12 Borodog

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Posted 20 January 2025 - 12:24 PM

There is no addtional image detail on the enlarged image as compared to the original version. So its sort of "empty" enlargement.

 

Indeed. But at that image scale gradations are visible in Chris's image that are not visible in yours, although perhaps some of that is an artifact of using the red channel as a luminance channel, which makes some kinds of detail more easily seen but wipes out other kinds. 


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#13 Jan_Fremerey

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Posted 20 January 2025 - 12:35 PM

up to 7X sampling

We should be aware that 7x sampling requires about 8x longer shutter times and 8x less frames within a given time as compared to 2.5x.
 



#14 Jan_Fremerey

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Posted 20 January 2025 - 12:46 PM

using the red channel as a luminance channel, which makes some kinds of detail more easily seen but wipes out other kinds. 

I agree, but I think over all number of perceivable details will increase which are no artifacts.
 



#15 Winteria

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Posted 20 January 2025 - 12:58 PM

How about when you match the overblown processing?

 

post-346195-0-62729400-1737392501.jpg


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#16 Jan_Fremerey

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Posted 20 January 2025 - 02:13 PM

How about when you match the overblown processing?

Ok, thanks, that's in fact quite a convincing improvement of Christopher Go's version in view of image detail. For better comparison we may increase image contrast in my version, but on larger scale Go's version certainly shows clearer image detail.

 

PS1: Please note that Go's image was taken one Jupiter revolution later than mine, so there should be some difference in cloud formation.

PS2: I think image scales should differ in correspondence with respective telecope apertures for fair comparison, ie 10:14 in the present case.

PS3: Would be iteresting to see what happens to 14" image detail when shortening camera adaptation by 50% and increasing image rate by factor 4.
 


Edited by Jan_Fremerey, 20 January 2025 - 05:16 PM.


#17 RedLionNJ

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Posted 20 January 2025 - 06:19 PM

We should be aware that 7x sampling requires about 8x longer shutter times and 8x less frames within a given time as compared to 2.5x.
 

If the seeing is good enough to support sampling at 7x pixel size, it's also likely good enough to support up to 25 or 30ms exposure time.


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#18 vidrazor

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Posted 21 January 2025 - 02:00 AM

So you suspect the double line to be an artifact? The fact that a short section of the double line can be vaguely recognized on the 16” image speaks against this.

If that looks floats your boat, I'm cool with it, but it's clearly ringing artifacts from over-sharpening.
 


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#19 Jan_Fremerey

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Posted 21 January 2025 - 06:39 AM

it's clearly ringing artifacts from over-sharpening.

By processing Christopher Go's 14" image Winteria was able to make the double line visible, so it appears to be real, ie no ringing artifact.



#20 Jan_Fremerey

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Posted 21 January 2025 - 08:52 AM

PS2: I think image scales should differ in correspondence with respective telecope apertures for fair comparison, ie 10:14 in the present case.

post-419811-0-61791900-1737395416_thumb_dSinc130_Vergleich_1.4.png



#21 Mitchell Duke

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Posted 21 January 2025 - 08:58 AM

What line are you describing? Can you draw a reference point around it? The other thing is what is the point of this subject? Just a question not being rude.

#22 Jan_Fremerey

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Posted 21 January 2025 - 09:33 AM

1. What line are you describing? Can you draw a reference point around it?

2. The other thing is what is the point of this subject?

1. It's the double line just above the northern cloud band:

 

ALPO-Eintrag_Marke.png

 

2. It was to demonstrate image resolution of 10" telescope with focal-ratio-to-pixel-size at 2.5 rather than 5-7 as recommended by the "5x rule", and comparing with 14" and 16" reference images by Christopher Go and Marco Guidi taken at the same time under "excellent" resp. "very good" seeing conditions.



#23 Jan_Fremerey

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Posted 21 January 2025 - 12:45 PM

it's clearly ringing artifacts from over-sharpening.

If it were a ringing artifact on the northern band, a certain spacing should appear more pronounced on the southern band (see green box), which is obviously not the case:

 

ALPO-Eintrag_2Marken.png


Edited by Jan_Fremerey, 21 January 2025 - 12:57 PM.


#24 Mitchell Duke

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Posted 21 January 2025 - 02:11 PM

Its not a artifact for sure. However times have changed since these shots have been taken. The cameras and telescopes have evolved. I disagree about 2.5x being better than 5x. Look at some of the most recent shots. Also look at some of my shots from this year in good seeing. Im a firm believer that 5x is where resolution / details are well resolved.
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#25 Jan_Fremerey

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Posted 21 January 2025 - 02:54 PM

1. The cameras and telescopes have evolved.

2. I disagree about 2.5x being better than 5x.

3. Also look at some of my shots from this year in good seeing.

4. Im a firm believer that 5x is where resolution / details are well resolved.

1. In particular, camera speed has much improved, so frame rates can be increased allowing 4x more frames to grab within given time at 2.5x than at 5x.

2. I just say and demonstrate that 2.5x is sufficient for matching telescope resolution.

3. Just became aware of your August 2023 Jupiter animation: excellent shots and processing!

4. No doubt about that.
 




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