From
David
M MOORE
© . . . . . . . . . . Subject: Mars - 24 April, 2003
All: First useable (probably
debatable!) Mars images this apparition. Was concerned the ToUCam may not be a good camera choice for a small Mars. It
is hard to adjust the image and not get a hot spot in Red. Focus does not
appear to be the same in all colors, as the Blue light images tend to be more
blurry. Hopefully, this is only a product of the seeing. After viewing Maurice Valimberti's images of Mars with the ToUCam,
I am hopeful this is the case. Awesome images for only 7.8" from down
under! See
http://elvis.rowan.edu/marswatch/images/2003-04.html
Does anyone have Maurice's
email address?
I hope to image soon with my HX-5 as
well. Am putting the finishing tweaks of
collimation on my 14" cass.
Thanks
(
© . . . . . . . . . .Date: Thu,
From:
"David M Moore" <davidpaulamoore@msn.com>
To: <vzv03210@nifty.com>
Subject:
Re: RE:Mars -
Masatsugu: Good hearing from you again. The issue of using the webcam
strictly for RGB purposes is probably not a good idea, hence the reason I want
to use my HX-5. The filtering over each pixel is probably not as stringent as
our RGB filters with IR blocker. Most assuredly, without the use of an IR
blocker, the Blue images are being tainted. I will experiment with an IR
blocker in the morning, seeing permitting. Perhaps the results will be better.
On second thought, that should prevent the Red images from being so hot and may
cut back on the distortion in Blue. Good idea Masatsugu! It will mean longer
exposures however, or more gain. Always a trade off!!
Of course, if my images are
worthy, please use them on your CMO website as you see fit.
Thanks for Maurice's email address.
© .
. . . . . . . . .Date: Thu,
From: Tim Parker <timothy.j.parker@jpl.nasa.gov>
Subject: Re: Mars -
Dave:
Have you tried splitting the RGB channels and re-registering them to compensate
for atmospheric refraction? I've done
this before with the 3com camera, and it works - to a point. The success will be limited because most
color ccds (the
Toucam, tou?) have cmy and green pixels (with green being by far the most abundant), where red AND blue are derived from the cyan and magenta filters
(so you can't really split them effectively). It would be interesting
to know whether any of the webcams use RGB on-chip
filter ccds.
But Apogee tried them without success (and Terry Platt says he experimented with the RGB color version of
the HX5's ccd, and found it too insensitive for low
light), so I guess I doubt this. Also, Mars is mostly red, and since the red
will always have some of the smear from refraction of the magenta filter across
the red-blue range, this might be part of the problem as well.
Wouldn't it be nice if there were a grayscale
version of the Toucam that you could use a filter
wheel with? (I guess you could "make" one by taking the IR block
filter out of the camera, using the one in your filter wheel instead, and
running the camera in "grayscale" mode).
planetary regards,
Tim PARKER (NASA)
© . . . . . . . . . .Date: Thu,
From:
"David M Moore" <davidpaulamoore@msn.com>
To:
"Tim Parker" <timothy.j.parker@jpl.nasa.gov>
Subject:
Re: Mars -
Tim: Thanks for your reply.
I have tried splitting the images and reopening them in Astroart,
messing with the histogram and restacking them.. I
have not yet tried to realign them in the manner you describe however. I will
try it next time.
Yes, I was just discussing the merits of
using the ToUcam for Mars with Masatsugu, and his
concerns regarding Blue images. I told him much the same as you have just
described. The chips do not use RGB pe se, but we
split them like it does. Not using an IR blocker, may well be part of the
problem too. I will try using a IR blocker in the
morning and see if this does not improve the Blue images and possibly stop the
hotspot in Red. Also, I doubt the filters over each pixel are very strict on
their exact wavelength preferences. There is some wavelength bleed over from
one filter to the next. I feel the webcams do a fine
job of extracting data in color for monitoring of overall changes and of course
the esthetics. For exacting purposes of studying Mars in specific wavelengths,
they no doubt fall short. This has been
a concern of mine.
Thanks
Dave MOORE (