From Christophe PELLIER
Subject: Reprocessed W47 Mars images
Hello to all
I have reprocessed
the three W47 images made at mid-september 2003 in a
new way that you could find interesting. While making some tests yesterday I
realized that the usual processing of my images, supposed to give fine details
but only average contrast, could be ill-suited for blue images and especially
the W47 shots. Here instead of using the third level of wavelet (Registax) I used the fourth one (up to 15). This gives only
gross details but a higher contrast ; what could be expected with blue images
of Mars (if not for RGB purposes) is not a highly detailed image but a highly
contrasted one, so in such a case this could be a good way of processing. The
images now seem to show much more white clouds. Note also that the signal to
noise ratio of the W47 images is now very good, unlike the previous versions.
This means that using such a filter, or any other shortwave solution, could be easier
than we thought, for Mars... On
Best regards
PS: a bit of technical data for these images:
B images : 10 fps, 1/25 sec., gain 50%. 3 mn AVI file and no selection.
W47 images : 5 fps, 1/25 sec., gain 50%. 4 mn AVI file and no selection.
With the
B&W webcam and 180 mm newtonian.
Cf: CPl’s images on 15
September 2003 and 16
September 2003.
® .
. . . . . .Date: Mon, 17 Nov 2003 11:47:13 +0100
From: "Paolo R. Lazzarotti"
To: Christophe Pellier
Subject: Re: Reprocessed W47 Mars images
Hello,
Chris!
Nice
to hear from you with a so interesting set of reprocessed images! The rule for
a correct processing is to work with the higher wavelet scale any time features
are low contrasted such as these ones.
A further specification.
Whenever you set 5, 10, 15 or 20 fps in your webcam and you select AUTOEXPOSURE
in the driver setting window, if light is low, the *real* exposure is,
respectively, 1/5, 1/10, 1/15 or 1/20 second. As soon you move the exposure bar
through the manual command, the integration is starting from 1/25 sec. as
displayed.
® . . . . . . .Date: Mon, 17 Nov 2003 19:04:26 +0100
Subject: Re: Reprocessed W47 Mars images
Hi Paolo, thanks for
the infos -
> A further specification. Whenever
you set 5, 10, 15 or 20 fps in your
> webcam
and you select AUTOEXPOSURE in the driver setting window, if
> light is
low, the *real* exposure is, respectively, 1/5, 1/10, 1/15 or
> 1/20 second.
> As soon you move the exposure bar
through the manual command, the
> integration
is starting from 1/25 sec. as displayed.
You are telling me
that if I set the exposition on AUTO, I can reach a longer exposure... 1/5 is
"much" longer than 1/25. Are you certain ? I
believed that a longer exposure than 1/25 could only be reached with some kind
of webcam modification... I do not really see a difference with some test I
have made, I still get a brighter image in manual (5 fps, 1/25 sec, 50 % gain),
than in auto (it seems that the gain is then put at
30%).
® .
. . . . . .Date: Tue, 18 Nov 2003 10:43:53 +0100
From: "Paolo R. Lazzarotti"
Subject: Re: Reprocessed W47 Mars images
Christophe Pellier
wrote:
>Hi Paolo, thanks for the infos -
>
>
>>A
further specification. Whenever you set 5, 10, 15 or 20 fps in your
>>webcam
and you select AUTOEXPOSURE in the driver setting window, if
>>light
is low, the *real* exposure is, respectively, 1/5, 1/10, 1/15 or
>>1/20
second.
>>As
soon you move the exposure bar through the manual command, the
>>integration
is starting from 1/25 sec. as displayed.
>>
>
>You
are telling me that if I set the exposition on AUTO, I can reach a
>longer
exposure... 1/5 is "much" longer than 1/25. Are you certain ?
>
Yes,
I am.
>
I
>believed
that a longer exposure than 1/25 could only be reached with some
>kind
of webcam modification...
>
No
HW modification is required; the long exposuring
drivers on the web make it "visible" to the users only. You can do
any exposition through any frame rate; here below the trick.
AUTO
mode ON - Select the exposition by the frame rate (the inverse is the
integration time in secs.) then, set the appropriate
gain level.
AUTO
mode OFF - now you can choose an eventually different frame rate -always equal
or lower than the previously one setted- and adjust
the gain, too.
NEVER
TOUCH THE EXPOSITION BAR ! ! !
On
this way, you'll be able to see an appreciable difference between 1/25 and 1/5!
This operation is valid with the Vesta and its
original driver, but I think the Toucam might do, too.
As soon you move the exposition bar in MANUAL mode, the integration highs up at
1/25 with no further chance to make it longer. You must repeat the above
commands.
>
I do not really see a difference with some
>test
I have made, I still get a brighter image in manual (5 fps, 1/25 sec,
>50
% gain), than in auto (it seems that the gain is then put at 30%).
>Christophe
>
Perhaps
you were not following the mentioned procedure! ;-)
Try
again!
® . . . . . . Date: Mon, 17 Nov 2003 19:06:43 +0100
Subject: Mars on november 16th 2003
Hi all, some images
taken last night under fairly good seeing.
http://astrosurf.com/pellier/2003-11-16-CPI
Best regards
Christophe PELLIER (Bruz,
