LtE in CMO #276
From Christophe PELLIER
® . . . . . . . . Date:
Subject: Re: RE:About the tilted blue filter
Dear Masatsugu,
here is the result of an experience I made on July 22 (I did not had time to
send it to you before). Under very good transparency I had decided to take a
second blue image with the filter tilted, just after having secured a
"classical" blue image ; so the conditions
are exactly the same. As seen here the tilted blue still shows the dark
markings; so on my side at least this method won't give the expected results. I
am more and more looking for a darker blue filter.
This morning the transparency was
very excellent (the seeing very poor) and I have even been able to see the dark
markings through the blue filter in visual. I was wondering if the transparency
of the atmosphere on Earth could also play a role in the G ghost in B ?
Best wishes,
® . . . . . . . .Date:
Subject: Mars July 23 and July 28 2003
Hello everyone
; I'm sending my latest images with a bit of delay due to my few days
out of town. On july 23 the
seeing was fairly good. On july
28, after days of rain, the transparency was excellent but the seeing very
poor. Moreover, a quick return of the rain that night didn't allowed me to take
more than two images. On these images you can see my first results with an
IR-pass filter.
http://astrosurf.com/pellier/2003-07-23-CPI
http://astrosurf.com/pellier/2003-07-28-CPI
Best regards,
® . . . . . . . .Date:
Subject: Re: RE:Mars July 23 and 28 2003
Dear Masatsugu,
I'm glad to read that you think
the RGB method is preferable. This is also my opinion. The LRGB (that is
usually an RRVB image now) will almost always erase the delicate atmospheric
features. This is something that I have deeply understood now. So it appears
that the yellowish haze noticed by Maurice was real. This just the kind of
feature that is extremely delicate to reproduce! But this is very, very
interesting. Yes, I should try to see those things in visual - the eye could
still be used to verify what the CCD shows, or doesn't show. Almost an
upside-down world... On the past weeks however I tried to witness visually the
morning and evening mist that you were talking about, but I failed to detect
it. My small instrument can give good images in CCD, but fails a bit short in
visual for critical observations. I will keep looking at the eyepiece, of
course, this is also merely espectacular. I now
realize that the last time I had good seeing on Mars was in 1997, and the
planet was very small then, so it's like if I was discovering Mars.
If you have time to do so, I
would like you also to explain me why the presence of white hazes makes the
dark markings more visible in blue... I don't see why right now.
Best wishes,
-----Message d'origine-----
De
: Masatsugu
MINAMI <VZV03210@nifty.ne.jp>
Date
: mardi 29 juillet 2003
Objet : RE:Mars
July 23 and 28 2003
>Dear Christophe,
>
>I should like first of all to praise your
images on 23 July just received. It
>is a wise way to choose RGB (instead of LRGB)
at this important hazy period,
>and these show well the vast expansion of
yellowish/white haze all over the
>surface.
Among a lot of easy ToUcammunists, you and Maurice
are normal or
>superb.
Your images well reproduce details while at the same time depict the
>present yellow hazed
situation well. I have looked forward long to this kind of
images.
>
>As to the tilting blue filter, I am now
inquiring of Dr OKANO. If you decline
>the filter by 20 degrees, you may move about
by 30nm, and so G ghost may
>disappear if the interference was well
performed, but as you say your
>comparison looks to bring no merit. Is it
beyond ToUcam, is it a true
>interference filter and so on?, but I cannot judge at present.
>
>However as I see your 23 July work, the B
image has to show vaguely the dark
>markings in this season because the whitish
haze is covering the surface (false
>blue clearing). At
this moment of the Martian season, you will not be able to
>kill the dark markings on B because the
whitish haze haunts outside. Usually
>whitish mist stay on the both sides but this
time airborne dust brings them
>deep toward the centre (near
>
>I like your 23 July images and I suppose they
are the best among a lot of work
>reached us recently. You were once a visual
observer, and so please try to
>watch by your naked eye the present status of
Mars, and then you will fine your
>images on 23 July are very real.
>
>More later,
>
>Send my regards to St Christophe,
>
>With best wishes,
>
>Masatsugu
>
® . . . . . . . .Date: Thu,
Subject: Re: RE:Re: RE:Mars
July 23 and 28 2003
Dear Masatsugu,
I hope that you have been
successful with the flares... I don't know if this could be caught from here in
the coming weeks.
If Elisabeth Siegel always see
the dark markings through the W47 this could be because her eyes are quite
sensitive to red wavelengths. The difference in sensitivity of the human eye
may so decrease the reliability of the evaluation of the "blue
clearing" through the same filter? On my side as I told you already, in
visual in full day I see purple markings through the W47, a color that
disappear if I add an IR-blocking filter, still in visual; and with the webcam this filter almost acts as an IR-pass filter !
Thanks for your further
explanation about the visibility of the dark markings in blue. If I don't see
the mists in visual this could be again because my instrument is a bit small
for this - nonetheless Mars is getting big and I should try again. The only
thing I see is a bright whitish following limb. I didn't caught either the
obscuration of the surface due to the yellow haze, although I know some people
made the statement recently that they found the dark markings less contrasted
than before. I do not, but I have not enough experience as a visual observer to
really judge. Six years of drawings is good for Jupiter, but not for Mars, as
it's visible only once every two years and also because no less than two
apparitions (1999 and 2001) have been plagued by poor seeing (in 1999 the
planet was still high in the sky but the seeing here during spring evenings is
generally poor).
The sun is going to shine for a
long from today, so I expect to observe again from this night.
******
In the recent weeks, and thanks
also to the paper copies of CMO that you sent me, I have been reading and
re-reading the 2001 CMO notes. I'm slowly understanding
the global explanation of the dust event that you have made; and I really think
that this work is just outstanding and thrilling.
Thank you for that.
Best wishes,
® . . . . . . . .Date:
Subject: Mars july 31 and
august 1 : best Mars again
Hi everyone : last night the
conditions were very good, and the planet is now so big ! This is truly espectacular to watch at the eyepiece.
Masatsugu : I think that this time the images clearly show the evening and morning
mist (first two RGB images) : this must be apparently because I have changed a
bit the exposure of the G and B images (increased at 1/33 and 1/25 instead of
1/50 and 1/33). The third RGB, made with the "old" settings doesn't
really show the mist. It seems that there is also a vast but subtle white haze
in the northern hemisphere. This is supported by the images taken with the
color Toucam; one of those two has been taken through
a pale blue filter to enhance the white hazes and mists (just an experience). I
have managed to see the mists in visual thanks to that filter. Note at last
that in the second RGB image the preceding part of Mare Cimmerium looks quite
obscured at the martian
evening.
Novus Mons is seen as a brilliant
white point (also seen in visual). It's also obvious that the IR images have a
lower resolution than the R ones.
To the Mars Observers group: I have trouble to access to my homepage so I can't give you a link
(the images will be visible on some others web pages soon), but I have uploaded
it in the "new images" folder (named 2003-08-01-CPI)
Best wishes,
® . . . . . . . .Date:
From: "Christophe Pellier"
<chrispellier@infonie.fr>
To: "Kunihiko OKANO"
<okano-k@mobile.email.ne.jp>
Cc: <VZV03210@nifty.ne.jp>
Subject: Re: Mars and
filters
Dear Kunihiko
Okano,
many thanks for your answer ! Sorry for the delay in my answer, I was a bit
away those days.
I'm interested to test your idea.
The thing I don't understand is why you're thinking about using those
You can send me the filters if
you wish, but only if it is at low cost for you.
I will receive in the coming days
another B filter, from Baader - it won't be of the
highest quality and will require an IRB filter to be used, but its transmission
seems to cut more the G than the Astronomik I have (it could be very similar to the SP6).
About the detection of martian
clouds and mists, it seems to me now that the ToUcam may be able to show them.
On many recent images I have seen, sometimes average, the morning and evenings
mists, and sometimes a yellowish haze, are showing. On my lasts observing
nights a big morning mist was easily detectable already on the raw movie. I
don't know if it is because the mists have grown a bit or because we are more
and more able to observe the martian
morning.
Best regards,
----- Original
Message -----
From: "Kunihiko OKANO"
<okano-k@mobile.email.ne.jp>
To: "Christophe Pellier"
<chrispellier@infonie.fr>
Cc: <VZV03210@nifty.ne.jp>
Sent:
Subject: Re: Mars and filters
> Dear Christophe Pellier
>
> Thank you
for your mail. Your images of Mars are superb.
>
> The sensitivity
of CCD in the range of 400nm-450nm is very important to take
> images of clouds. If the sensitivity of CCD in this range is
low, the effect of
> tilting
may be insignificant. As you pointed out, the tilting of filters also
> results in the shift of IR leak band, therefore the IR
blocker is always
> required,
even if the B filter itself has IR block function.
>
> My latest idea
is to use a plastic filter with an interference B filter. I am
> planning
to use FUJI-film's Tri-Acetate filter SP-4 with the SBIG or IDAS B
> filter.
Unfortunately, I did not test this idea yet because
> the rainy season.
>
> I attached the
charts of band pass of SP-4 and SP-6. The transparency by SP-4
> +
interference B filter will attain 80% at the peak. The SP-4 may be the best
> for ST-7ME (high sensitivity in 400nm-450nm range), but the
SP-6 will be
>
recommended if the sensitivity in 400nm-450nm range is low, like my ST-5C
> camera.
>
> The
> availability in
> pieces (30mmx30mm) of SP-4 and 6 via air-mail. I am sure
that the condition of
> sky of your observatory is much better than
>
> Sincerely
> Kunihiko OKANO
® . . . . . . . .Date:
Subject: Re: FW:Mars -
Dear Masatsugu: thanks for
forwarding me images. I see that the haze is becoming important. I wonder where
it will lead the planet...
Regards
® . . . . . . . .Date:
Subject: Mars august 4 2003
Hi all :
here is the latest. Seeing was fair and the transparency almost poor: hard time
for the blue filter! The haze and mists are still visible nonetheless.
Best wishes
® . . . . . . . .Date:
From: "Christophe Pellier"
<chrispellier@infonie.fr>
To: "Kunihiko OKANO"
<okano-k@mobile.email.ne.jp>
Cc: <VZV03210@nifty.ne.jp>
Subject: Re: Mars and
filters
Thank you !
So effectively an IR blocking filter won't be enough.
Best regards
>
> This is
because the SP-4 has a second passband in the range
of 580nm-700nm, that
> is, the
SP-4 is Magenta filter. Transparency of any Blue plastic filters is
> usually low (<50%). This is the reason why I use the SP-4
+ interference blue .
>
> Sincerely
> Kunihiko OKANO
® . . . . . . . .Date: Thu,
Subject: Mars august 6 2003
Hi all :
on august 6 the seeing this time was fairly good, nonetheless the transparency
is still fair. The images still barely show the yellow-white haze (very faint).
Note also the Olympus Mons just visible on the first RGB serie.
http://astrosurf.com/pellier/2003-08-06-CPI
Regards
® . . . . . . . .Date:
Subject: Re: About
Green
Dear Masatsugu:
many thanks for having taken time to write to me your thoughts about the
green. I would add something, I think, that the G filter must be more efficient
at showing a dust haze (not dust clouds). If the martian atmosphere is dusty, the red filter might go
through this, while it will show better on the green image. This is something I
saw on Don Parker's images of the dust clouds in early july, and on my last images the yellow haze shows in
the green images. So that could be also a further argument against the R(G)B method. About the mists, those last days the
transparency was too poor to really see them but otherwise I'm at least able to
detect them with the help of a light blue filter (I saw the mists on august
1st).
Best wishes
® . . . . . . . .Date:
Subject: Re: RE:Re: About Green
Dear Masatsugu,
thank you for showing me Okano's last excellent shot. I would like also to
have a further explanation of his G image ! For the B
image the transparency of the sky is indeed very important. I have problems
here because of that, our last high pressure system has brought too much hot
and the sky has been dusty-like (same as Mars !) for
one week at least. I had to adopt different settings with the webcam, that
work OK nonetheless, the yellow haze is still there on the images. In visual
this situation makes martian
clouds very difficult to see.
I agree that the G image is more
important when there is dust to detect. Right now I'm convinced than any R(G)B image will totally fail to show the subtle dust haze.
I'm sending images from last
night with another e-mail.
Best wishes
® . . . . . . . .Date:
Subject: Mars august 9 2003
Hi all - my sky is very hazy but
the big diameter of the planet and some changes in the setting of the webcam still allow me to get some detailed images. The
seeing was fair, nonetheless it was that kind of very
small air turbulence that doesn't erase the details too much. Note that there
are still very faint orographics forming over
Tharsis.
http://astrosurf.com/pellier/2003-08-09-CPI
Regards and stable skies
Christophe PELLIER (Bruz,
