LtE in CMO #281

FromChristophe PELLIER


. . . . . . .Date: Mon, 13 Oct 2003 21:35:40 +0200

Subject: Re: RE:CMO news ?


Dear Masatsugu, first congratulations for your 840+ drawings. I hope that you will exceed the thousand ! On my side I don't really hope to reach one hundred of images sets (that would mean 100 nights of observations, and the weather still has a bad look). Thanks very much for sending me some of your drawings, they depict very well how the dust was going on in early july. I'm quite desperate not to have witnessed any dust so far, except just a little bit in the first july observations !


Thank you for allowing me to use your sentences. Many thanks also for your article about the blue layer, it really teaches me many things. I feel quite uneasy with the idea of blue clearing and I never make such comments on my images. As you points out there are many factors that can explain that we see the dark markings in blue. On my side the question I would have is, where is the pertinent wavelength point where we should say that the atmosphere in blue is more clear than the day or the month before !


Now about the spots :


1) The dark spot near Hellas. Are you thinking of a possible pre-storm phenomenon? I have checked more images and it seems that it has been permanent. On Tan's image of 2001 the dust storm in and near Hellas was already much active so it could have been one of those darkened details by dust removal. And the problem with the images of july 31- august 1st is that the spot different in G than in R in the second RGB serie appears the same in both color in the third RGB serie.


2) The white spot on the september 16th images. This spot is real: I have seen an image taken by another french observer on same night where it is also visible. My logical reasonment was that a white spot in a color image visible in every color, especially in red, should be a frost deposit. It is situated near 100W, 46N, very close to Alba Patera, but I see no crater that could for example explain it.


It sounds extraordinary to me to detect such a thing but there have been many unexpecting details detected this year it seems. I think that there is also "something" on my september 15th images near the same place.


I'm happy to know that the few images made with the W47 has been appreciated a little because it's rather ungrateful to use such an absorbing filter !


Would you be kind enough to explain me what were Okano's comments about SP-4, SP-6 and W47 ? I would be very, very interesting to know his analysis. I did not received the SP-4, which seem to be unknown at the Fuji French homepage, but however I can use the W47 or another deep blue filter bought from Schuler. It's sad that the CCDs are so insensitive to short wavelengths.


About the dust veil: I strongly hope that my images will show the obscured evening limb, if the sky ever clear on the following weeks. I have been, however, recently wondering about this veil, if it was still there or not. Of all the color images I have made, it seems that only two show it with certainty (23 july and the second RGB of august 11th). It's one of the most difficult detail to reproduce. My interrogation came because if I'm not mistaken, there are more white clouds now on the planet than in july-august. If true, can't this be a proof of a dust settling ? Without any dust cloud to stir it again since the end of july, it can't stay in the atmosphere for ever... The blue images of november-december 2001 seemed to show also an increase in white clouds while the obscuration was ending.


Best wishes


PS About the enfant terrible, your french culture looks very wide... Did you mean something particular !!


. . . . . . .Date: Mon, 13 Oct 2003 21:41:39 +0200

Subject: Mars October 11 2003


Hi all, for the last clear night the seeing was again very poor.

The morning Hellas is still yellowish.




. . . . . . .Date: Sun, 19 Oct 2003 14:29:52 +0200

Subject: Mars, october 17 2003


Hi all, some images taken under correct conditions, better than my previous two sets of this month but still not satisfying ! The IR images have been realized by stacking the W47 with the RG610. It sounds unusual but actually it works... Also an attempt of making a true LRGB image.




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

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