LtE in CMO #276

From Christophe PELLIER


. . . . . . . . Date: Tue, 29 Jul 2003 01:20:05 -0000

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: Tue, 29 July 2003 14:55:14 -0000

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.


Best regards,


. . . . . . . .Date: Wed, 30 Jul 2003 00:32:51 -0000

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 <>

Date : mardi 29 juillet 2003 13:53

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 noon) and as well as to the whole disk.


>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,





. . . . . . . .Date: Thu, 31 July 2003 12:56:10 -0000

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: Sat, 2 Aug 2003 00:13:45 +0200

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: Mon, 4 Aug 2003 20:53:37 +0200

From: "Christophe Pellier" <>

To: "Kunihiko OKANO" <>

Cc: <>

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 Fuji filter in conjunction with a B interference filter, the transmission curves of the SP4 and SP6 look already quite good? If it is to block the IR, then an IRB filter would be fine. Please tell me.


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" <>

To: "Christophe Pellier" <>

Cc: <>

Sent: Friday, August 01, 2003 5:40 PM

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 Tokyo is still in

> 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 FUJI's filters are widely available in Japan, but I don't know the

> availability in France. If you could test this idea, I would like to send you

> 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 Tokyo (:>).


> Sincerely

> Kunihiko OKANO


. . . . . . . .Date: Mon, 4 Aug 2003 21:27:39 +0200

Subject: Re: FW:Mars - August 03, 2003


Dear Masatsugu: thanks for forwarding me images. I see that the haze is becoming important. I wonder where it will lead the planet...



. . . . . . . .Date: Tue, 5 Aug 2003 01:23:33 +0200

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: Tue, 5 Aug 2003 20:51:33 +0200

From: "Christophe Pellier" <>

To: "Kunihiko OKANO" <>

Cc: <>

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, 7 Aug 2003 13:24:08 +0200

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.



. . . . . . . .Date: Fri, 8 Aug 2003 21:13:43 +0200

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: Sat, 9 Aug 2003 23:12:40 +0200

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: Sat, 9 Aug 2003 23:28:28 +0200

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.


Regards and stable skies


Christophe PELLIER (Bruz, Ille-et-Vilaine, France)

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