The last saturn of the season

Hi to all!Here there is my last saturn image:
http://www.marcofazzoli.com/danieleg...urn_050322.htm
Perhaps this is the last one cause the bad weather and the approach of
the planet to the Sun, but I think this is also my best Saturn image
ever taken.
I used my C 9,25+barlow apo 2X (f30) and my philips vesta pro scan.
Mean of 1700 frames at 15 fps.
I hope you like it!
Clear skies

Daniele Gasparri
Perugia (Italy)
www.marcofazzoli.com/danielegasparri

Fantastic!

"Daniele Gasparri" wrote in message
news
Hi to all!Here there is my last saturn image:
http://www.marcofazzoli.com/danieleg...urn_050322.htm
Perhaps this is the last one cause the bad weather and the approach of
the planet to the Sun, but I think this is also my best Saturn image
ever taken.
I used my C 9,25+barlow apo 2X (f30) and my philips vesta pro scan.
Mean of 1700 frames at 15 fps.
I hope you like it!
Clear skies

Daniele Gasparri
Perugia (Italy)
www.marcofazzoli.com/danielegasparri


I don't want to degrade from the image, as it is certainly very good, but
lots of artifacts are present. Anything captured beyond 5 fps with a
standard webcam produces artifacts. I can certainly understand the motive
though as 5 fps doesn't do for Saturn in many areas but even 10 fps is
better than 15. With Saturn, artifacts often appear in the rings themselves
once the image is sharpened and this image is no exception.

Sorry- I didn't mean to cause the rain to fall here- but overprocessing and
improper image acquisition has become commonplace since digital imaging has
taken the forefront.

On a positive note, there are now some cameras capable of capturing at
faster frame rates without producing artifacts but I have yet to see any of
these more expensive cameras offer better light grasp than a b&w webcam.
Unfortunately, this translates to having to use much higher gain, which
undermines the no artifact capability. You can only push current CCDs so
far.

Jason Washburn

On Mon, 11 Apr 2005 17:35:52 GMT, "Jason Washburn"
wrote:

I don't want to degrade from the image, as it is certainly very good, but
lots of artifacts are present.

Huh? What artifacts? This is one of the best amateur images of Saturn
I've ever seen. It is simply stunning.

*All* the detail in the image looks real to me when I compare
Daniele's photo to the visible image in the follow HST pic:

http://imgsrc.hubblesite.org/hu/db/2.../large_web.jpg

---
Michael McCulloch

"Michael McCulloch" wrote in message
news
On Mon, 11 Apr 2005 17:35:52 GMT, "Jason Washburn"
wrote:

I don't want to degrade from the image, as it is certainly very good, but
lots of artifacts are present.

Huh? What artifacts? This is one of the best amateur images of Saturn
I've ever seen. It is simply stunning.

*All* the detail in the image looks real to me when I compare
Daniele's photo to the visible image in the follow HST pic:

http://imgsrc.hubblesite.org/hu/db/2.../large_web.jpg

Well, to be honest, that is the current debate: whether or not many of the
digital images being produced today, especially from webcams, are producing
real images or images mixed with artifacts. One reason artifacts are
present in this image is because it is a well known fact that anything
beyond 5 fps with a standard webcam produces them. I don't know the website
address offhand, but a google search for "K3CCD Tools" will bring up Peter
K's site where he thoroughly tested webcam speeds several years ago and did
show that artifacts were present beyond 5 fps. I myself used to notice the
artifacts at 15 fps when I tried to image Jupiter several times- and such
images required processing to remove the artifacts.

With Daniele's image, there may be many details that match up with the
Hubble shot, but there are too many ring divisions and unnatural
brightnesses present- a common problem when processing Saturn. There should
not be, for example, a very bright inner ring at the front of the wider
ring, nor should it look like there's more than one Encke minima and to me
it does.

Now, let me reemphasize that I'm not saying I don't like the image- I do-
but I think there's a fine line between what's really there and what's being
artifically created through processing.

Jason

---
Michael McCulloch

Michael McCulloch wrote:
Huh? What artifacts? This is one of the best amateur images of Saturn
I've ever seen. It is simply stunning.

*All* the detail in the image looks real to me when I compare
Daniele's photo to the visible image in the follow HST pic:

http://imgsrc.hubblesite.org/hu/db/2.../large_web.jpg

I disagree. I think Jason is right.

There are two basic types of artifacts that I see in Daniele's image.
The first is some uncleaned background differences--maybe it's a two
or three-part mosaic. This is entirely unobjectionable.

More serious are what I see to be overprocessing artifacts. There
are two telltale signs: one is a spurious ring outside the A ring (I
absolutely guarantee that is *not* the F ring), and the other is the
presence of symmetric intensity fluctuations within each boundary of
the A and B rings.

I think this is the result of somewhat overzealous unsharp masking.
Suppose you have this input intensity profile:

***************
*
*
*
***************

The PST of the instrument, as well as atmospheric turbulence, will
cause this profile to be recorded as

***********
***
*
***
***********

Ideally, you'd like to recover the original through processing, but
because some information is lost, that's not possible. If you don't
process enough, you will still have a sloped profile, but you can
also process too much. This gives you a profile something like this:

*** *******
* ***
*
*** *
******* ***

That's what I see in Daniele's image--good though it may be. Note
the modest peak in brightness at the center of the A ring in his
image--that is just where the ring is actually dimmer within the Encke
minimum. Then, too, his image shows a dimming at the edge of the A
ring, which you might think is the Encke division, about 80 percent of
the way out, but note that his image has a similar dimming about 20
percent of the way out as well, where the A ring is actually brighter.

That's not to say that Daniele hasn't captured a good image; he has.
But there *are* visual artifacts. Is Maurizio di Sciullo well enough
to image? I seem to recall he struck a good balance between recovering
contrast and avoiding artifacts.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Jason Washburn wrote:



Hi Jason and thank you for the comment!
Yes, I saw that with the webcams especially with high framerate it's
very easy to produce artifacts and with a strong processing they become
visibles and irritating. Indeed find an appropriate processing for my
saturn was very difficult. I though to have deleted (or better, hidden!)
the main artifacts.
Well, to be honest, that is the current debate: whether or not many of the
digital images being produced today, especially from webcams, are producing
real images or images mixed with artifacts. One reason artifacts are
present in this image is because it is a well known fact that anything
beyond 5 fps with a standard webcam produces them. I don't know the website
address offhand, but a google search for "K3CCD Tools" will bring up Peter
K's site where he thoroughly tested webcam speeds several years ago and did
show that artifacts were present beyond 5 fps. I myself used to notice the
artifacts at 15 fps when I tried to image Jupiter several times- and such
images required processing to remove the artifacts.
This is very interesting.I see that webcam are very delicate and
especially in my city I have to screen it from the external noise and
connect it to the earth, otherwise the image is very very noisy and full
of artifacts.
I'm thinking to change my webcamsbut the prices are very high!I saw the
results obtained with Lumenera Lu075 (see www.astromeccanica.it for
astronomical use and http://www.lumenera.com/ for better description of
the camera). This CCD is without any doubt better than webcams but I
need more information about its astronomical use.

With Daniele's image, there may be many details that match up with the
Hubble shot, but there are too many ring divisions and unnatural
brightnesses present- a common problem when processing Saturn. There should
not be, for example, a very bright inner ring at the front of the wider
ring, nor should it look like there's more than one Encke minima and to me
it does.

I don't know if they are artifacts (maybe yes!)..this is difficult to
say. I have more images taken the same evening and all show these
divisions, but this is not enough to exclude that they are not artifact.
This problem is common in many images like Damian Peach.
I think find solution for this problem will be very difficult!

Now, let me reemphasize that I'm not saying I don't like the image- I do-
but I think there's a fine line between what's really there and what's being
artifically created through processing.

I understand perfectly, and I thank you again.
Jason



Daniele Gasparri
Perugia (Italy)
www.marcofazzoli.com/danielegasparri

"Brian Tung" wrote in message
...
Michael McCulloch wrote:
Huh? What artifacts? This is one of the best amateur images of Saturn
I've ever seen. It is simply stunning.

*All* the detail in the image looks real to me when I compare
Daniele's photo to the visible image in the follow HST pic:


http://imgsrc.hubblesite.org/hu/db/2.../large_web.jpg

I disagree. I think Jason is right.

There are two basic types of artifacts that I see in Daniele's image.
The first is some uncleaned background differences--maybe it's a two
or three-part mosaic. This is entirely unobjectionable.

More serious are what I see to be overprocessing artifacts. There
are two telltale signs: one is a spurious ring outside the A ring (I
absolutely guarantee that is *not* the F ring), and the other is the
presence of symmetric intensity fluctuations within each boundary of
the A and B rings.

I think this is the result of somewhat overzealous unsharp masking.
Suppose you have this input intensity profile:

***************
*
*
*
***************

The PST of the instrument, as well as atmospheric turbulence, will
cause this profile to be recorded as

***********
***
*
***
***********

Ideally, you'd like to recover the original through processing, but
because some information is lost, that's not possible. If you don't
process enough, you will still have a sloped profile, but you can
also process too much. This gives you a profile something like this:

*** *******
* ***
*
*** *
******* ***

That's what I see in Daniele's image--good though it may be. Note
the modest peak in brightness at the center of the A ring in his
image--that is just where the ring is actually dimmer within the Encke
minimum. Then, too, his image shows a dimming at the edge of the A
ring, which you might think is the Encke division, about 80 percent of
the way out, but note that his image has a similar dimming about 20
percent of the way out as well, where the A ring is actually brighter.

That's not to say that Daniele hasn't captured a good image; he has.
But there *are* visual artifacts. Is Maurizio di Sciullo well enough
to image? I seem to recall he struck a good balance between recovering
contrast and avoiding artifacts.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Brian,

I think you beautifully illustrated a point I wanted to make earlier: that
the digital imaging process always involves some amount of loss, no matter
how good the CCD, conditions, circuitry, etc. Anytime a circuit is used to
convert from analog to digital or reverse, there is loss. Of course, it's
better to have a greater bit conversion, like a 16 bit CCD camera, but the
loss never eliminates- it is reduced only. A webcam is only 8 bit to start
with and the idea behind stacking is to minimize noise and increase depth
(and help replace the missing information), but oversharpening will bring
back out anything missing or artifically created.

I've often wondered why more folks haven't tried stacking film images. I
realize the process is a lot tougher, and there is in fact loss once the
film is scanned into digital, so maybe the tedious film idea isn't worth it.

I see that Meade has come out with a reasonable cost monochrome 16 bit CCD
camera, but then again the limitation here is speed at it's only capable of
5 fps maximum.

Ideally, the only ways around artifacts are using the camera at the proper
frame rate and having truly good seeing conditions, with the latter,
unfortunately, occurring rarely for many locales.

Jason

"Daniele Gasparri" wrote in message
...


Jason Washburn wrote:



Hi Jason and thank you for the comment!
Yes, I saw that with the webcams especially with high framerate it's
very easy to produce artifacts and with a strong processing they become
visibles and irritating. Indeed find an appropriate processing for my
saturn was very difficult. I though to have deleted (or better, hidden!)
the main artifacts.

Saturn is probably the toughest planet to properly process. It also lies at
the edge of the webcam's sensitivity, so noise can be a problem also.

Well, to be honest, that is the current debate: whether or not many of
the
digital images being produced today, especially from webcams, are
producing
real images or images mixed with artifacts. One reason artifacts are
present in this image is because it is a well known fact that anything
beyond 5 fps with a standard webcam produces them. I don't know the
website
address offhand, but a google search for "K3CCD Tools" will bring up
Peter
K's site where he thoroughly tested webcam speeds several years ago and
did
show that artifacts were present beyond 5 fps. I myself used to notice
the
artifacts at 15 fps when I tried to image Jupiter several times- and
such
images required processing to remove the artifacts.
This is very interesting.I see that webcam are very delicate and
especially in my city I have to screen it from the external noise and
connect it to the earth, otherwise the image is very very noisy and full
of artifacts.
I'm thinking to change my webcamsbut the prices are very high!I saw the
results obtained with Lumenera Lu075 (see www.astromeccanica.it for
astronomical use and http://www.lumenera.com/ for better description of
the camera). This CCD is without any doubt better than webcams....

I wouldn't go that far. The CCD used in the Lumenera is actually not as
sensitive as a monochrome based webcam (a webcam modified to use a b&w
sensor). The only advantage that camera offers is speed, but the gain is
definitely not there. Many frames still have to be stacked to overcome
noise. A b&w Unibrain uses a b&w version of the Toucam CCD and can record
uncomprssed at higher frame rates, but this low cost camera has had some
problems- otherwise, it would be the ideal candidate.

but I
need more information about its astronomical use.

It uses the ICX424 sensor. To get that camera to the same focal length as a
webcam would require a magnification boost which means less gain available.
Once the focal lengths are equalized, the gain is less than a monochrome
webcam.

With Daniele's image, there may be many details that match up with the
Hubble shot, but there are too many ring divisions and unnatural
brightnesses present- a common problem when processing Saturn. There
should
not be, for example, a very bright inner ring at the front of the wider
ring, nor should it look like there's more than one Encke minima and to
me
it does.

I don't know if they are artifacts (maybe yes!)..this is difficult to
say. I have more images taken the same evening and all show these
divisions, but this is not enough to exclude that they are not artifact.
This problem is common in many images like Damian Peach.
I think find solution for this problem will be very difficult!

There really isn't a processing solution- only the best seeing can cure it.
Unfortunately, 9/10 seeing occurs rarely throughout most parts of the world.

Now, let me reemphasize that I'm not saying I don't like the image- I
do-
but I think there's a fine line between what's really there and what's
being
artifically created through processing.

I understand perfectly, and I thank you again.
Jason



Daniele Gasparri
Perugia (Italy)
www.marcofazzoli.com/danielegasparri

On Mon, 11 Apr 2005 18:20:00 +0000 (UTC), (Brian Tung)
wrote:

I disagree. I think Jason is right.

There are two basic types of artifacts that I see in Daniele's image.
The first is some uncleaned background differences--maybe it's a two
or three-part mosaic. This is entirely unobjectionable.

Ok, agree but that really is more of a function of your monitor's
brightness/gamma relative to Daniele's. I didn't notice that at all on
my monitor until I copied the image to Photoshop and then turned up
the brightness.

More serious are what I see to be overprocessing artifacts. There
are two telltale signs: one is a spurious ring outside the A ring (I
absolutely guarantee that is *not* the F ring),

Again, this was not visible on my monitor until I turned up the image
brightness. Obviously Daniele tuned this image for his monitor
settings -- totally defensible.

and the other is the
presence of symmetric intensity fluctuations within each boundary of
the A and B rings.

I'm not 100% convinced of this argument, and the effect is very
subtle. Many observers (i.e. visual) and pictures I've seen show the 3
concentric dark shadings in the B ring which do not show up in the
Hubble photo with nearly the same contrast.

Just for kicks I've put the following image up on my server
temporarily. The top image is Daniele's and the bottom is the Hubble
pic resized. (Note: this is only temporary for the sake of argument, I
have no intentions of stealing Daniele's work. I also realize the
black level is slightly different.)

http://gamesforone.com/pictures/compare.jpg

One thing I immediately notice is that the Encke division essentially
disappears from the Hubble photo at the same image scale. Does that
mean the Encke division is an artifact too?

Annotate the image I posted and show me what you believe are
artifacts. I'm seriously interested in this topic since I aspire to
take similar photos, and have done a few, and want to better train my
eye if you guys really have a valid argument.

---
Michael McCulloch