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Mars on May 3rd

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#1 stanislas-jean

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Posted 04 May 2014 - 11:43 AM

A report for Mars done last 3rd May with the 100mm refractor and the cassegain 254mm for a confirmation.
At the best images were just average to poor.
Stunning color of the disk: yellowish.
Stanislas-Jean

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#2 SteelStar

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Posted 04 May 2014 - 05:12 PM

Very nice. Observed Mars the 2nd and 3rd of May as well. Syrtis Major was easily seen with my 6" refractor and 12" dob.

Great sketches

#3 Tommy5

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Posted 04 May 2014 - 07:30 PM

Very nice Mars sketch, good detail, thanks for sharing.

#4 CarlosEH

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Posted 05 May 2014 - 01:35 AM

Stanislas,

Thank you for your excellent observations of Mars. Am I to assume that your noting the disk to be yellowish that the atmosphere of Mars is very dusty? I know that there is a polar vortex at this time.

Regards,
Carlos

#5 stanislas-jean

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Posted 05 May 2014 - 03:44 AM

Thanks everybody for your witnesses.
Carlos, regarding the overall color of Mars disk, this was noted without comment about. This looked abnormal for me.
This was the reason of the use of the 254mm cassegrain for the confirmation.
However I note the brillance of the white clouds at limb also in yellow and at a lesser level in red color. Also this patch on Tharsis area in red color that I attribute to be fresh depositions on ground. Overall atmosphere dusty with a certain density, why not, but difficult to proove with the observations.
The polar vortex needs to be followed in lot of colors including the violet and NIR, from my opinion.
I donot see pure white clouds, but charged of dense dust.
Stanislas-Jean

#6 niteskystargazer

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Posted 06 May 2014 - 11:22 AM

Stanislas-Jean,

Very nice sketches of Mars on May 3rd :).

CS,KLU,

:thanx:,

Tom

#7 Ed D

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Posted 06 May 2014 - 08:50 PM

Stanislas, very good and informative sketches. I have also recently noticed something different about the hue and views of Mars, but I assumed it was my local observing conditions. Hmmm, I want to follow up on this one.

Stanislas, Carlos; thanks for the info.

Ed D

#8 Uwe Pilz

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Posted 06 May 2014 - 11:29 PM

The sketches gives a good im pression of how faint the features at Mars are. Thank you for sharing.

#9 stanislas-jean

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Posted 07 May 2014 - 12:58 AM

Thanks Tom, Ed and Uwe.
Regarding the overall color of the disk this appeared abnormal to me. I cannot get data in the mean time, weather on Paris area is stormy. When catching this color I was wandering if the W11 filter remained in the eyepiece holder, indeed not.
There are other singularities on the present opposition, like the presence of long terme limb white appearing clouds which are bright too in yellow. If you watch at the area on Tharsis and around, a patch appeares clear in red color like something had been changed on the ground. I attributed this with the presence of mist. Where is coming the dust? From the polar cap thawing which is surely a mixture of dusty snow-ice producing these mist by sublimation and in spite of the sublimimation processus that acts by definition as distilation.
Returning on this vortex event, it would be interresting to analyse in different color the reflectivity of the vortex, to see if this is dusty too.
Just a proposition.
Stanislas-Jean

#10 Ed D

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Posted 07 May 2014 - 07:59 PM

Stanislas, I had good conditions last night and was able to observe for a while with my C102 achromat. The color of the planet definitely looks different, being more of a yellow color than the pink or peach we have been observing. It also appears to me that the albedo features are slightly subdued and not quite as contrasty as I have been observing them. A dusty atmosphere could certainly be a factor.

I could not detect any significant difference between unfiltered and filtered views using my #8 light yellow. I believe this may be indicative of an atmosphere with a higher fine dust content. I tried the #82A light blue filter and it did not have the effect I was anticipating. The NPC and white southern hood/Hellas did not 'pop out' with the blue filter as they normally do. Again, this may be indicative of an atmosphere charged with fine dust. I believe the dusty veil would tend to diminish the contrast effects the #8 and #82A filters would normally have.

Provided that I correctly understood the weather patterns and processes Jeff Beish describes in his Mars handbook (and other resources I have read), it would seem to be consistent that the atmosphere would be currently charged with fine dust. Many of the most recent sketches and photos posted seem to support a currently dusty atmosphere, showing a very light yellowish veil over the planet regardless of scope type or aperture.

Ed D

#11 frank5817

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Posted 07 May 2014 - 08:29 PM

Stanislas,

Wonderful detailed sketches.

Frank :)

#12 stanislas-jean

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Posted 08 May 2014 - 04:33 AM

Thanks Ed and Frank.
I had a look on Mars yesterday evening with a window of 2 hours.
In first, looking at Mars with naked eyes, it appeared also yellowish and not the orange-red usual color.
I used the 254mm cassegrain for the report performed at 238x, more was not possible (the 312x too blurring with the seeing). The overall disk color was not usual and I confirm my observations of the 3rd with some adds, considering the observation in IL.
Generally, for all channel color observed, especially the red, the contrast levels are poor. Mare around Solis Lacus, Aonius, Sirenum were almost un-perceptible. Mare Boreum around the cap was not conspiscious. All the half tones features represented on the temperate area looked very low contrasted, Nikokeras and surroundings too, Elysium at the limb whitish with dark boundaries looked also low contrasted (seemed reinforced by the transition white dark boundaries, etc...
The best views were under the blue filter (relatively), and exceptionally poor in contrast under the red filter, the yellow at a lesser intensity.
Indeed the sketches seems to show hard contrasts, enhanced here for showing the difference between colors.
I remembered the vision of Syrtis Major during the great dust storm where it disappeared almost. I saw it in spite of in the 100mm refractor when its contrast was around 3% only. This was near a limit. Here on the 7th May, yesterday, we can attribute a level contrast of the features staying on the temperates zones to be say 5% more or less.
I we try to attribute a density of atmosphere attenuation, this could be minimum 50% (those features under clear atmosphere turn around 10% level). The tendency, stronger in red color surely.
Therefore in addition to the white hazze we see due to season occurences, there is an amount of dust with a non-negligeable density.
This is a fact.
Where is coming this dust:
- cap thawing speed very high, sothat dust are transported by the white hazze,
- deep white clouds at equator limbs crearing strong convections from the ground (we saw in yellow-red colors patches of bright ground area when white clouds disappeared).
Interresting to follow.
Yes Ed I confirm your observationnal points.
Thanks for your post.
Stanislas-Jean

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