Re: The last saturn of the season


"Daniele Gasparri" <danielegasparri@xxxxxxxx> wrote in message
news:qfz6e.766343$b5.34300389@xxxxxxxxxxxxxxx
>
>
> 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
>


.

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