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Mars - 11th April 2012

dweller25

By dweller25
in Sketching

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dweller25

dweller25

Posted
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Well the clouds thinned down with clear gaps in between so I took my chances and set up the 8" Dobsonian to have a look at Mars.

Seeing was superb AII - very steady indeed and Mars although rapidly shrinking in size showed a lot of detail.

Because the seeing was so good I could get a sharp image even at high magnifications.

Then had a look at Saturn which is very low but before any detail could be seen the clouds rolled in ......

Mars made a great sight.

Skywatcher 8" F/6 Dobsonian at x343 plus Neodymium filter.

11th April 2012 at 2100UT, seeing AII

post-13701-133877761815_thumb.jpg

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durval

durval

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Hello,

Then had a look at Saturn which is very low but before any detail could be seen the clouds rolled in ......

[...] Skywatcher 8" F/6 Dobsonian at x343 plus Neodymium filter.

11th April 2012 at 2100UT, seeing AII

Congratulations! This is one great sketch, it shows a lot of detail and at the same time feels very pleasing and natural.

Just one question: is it in "normalized" orientation, ie, North is up and East is right?

Thanks in advance for the clarification,

--

Durval.

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durval

durval

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Hi,

Hello Durval, thanks for the kind comments.

Below is the same drawing labelled up as p (preceeding), f (following), n (north), s (south)

Hope that helps.

Thanks for the quick response! My main interest was to validate a rough sketch I did of Mars on the same day and approximately the same time as yours. My seeing was so much worse that the 3 dark features you recorded to the N of Mar's equator were jumbled together at my eyepiece and seemed more like a single, large, "foot-like" feature... the white N polar cap was also much more spread on the N "tip" of the sphere, instead of contained in a small area like on your sketch. And I used a larger dobsonian (a 10in f/5) than yours... This only goes to show that, when observing planets, seeing really rules... and in bad seeing, more aperture can indeed be detrimental...

Cheers,

--

Durval Menezes.

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durval

durval

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Hello David,

Please post your sketch......

Here it is: I took the time to redo it in GIMP as my hand-made sketch was so ugly it was unpostable (not that this one is much better, specially compared to yours).

On the other hand, it illustrates fairly well what I saw at the eyepiece, to wit:

(...)the 3 dark features you recorded to the N of Mar's equator were jumbled together at my eyepiece and seemed more like a single, large,"foot-like" feature... the white N polar cap was also much more spread on the N "tip" of the sphere, instead of contained in a small area like on your sketch.

Regarding the large differences in our observations, do you think it's all explainable by seeing? Or are planetary features always difficult to resolve visually, specially on a "small" (at the eyepiece) planet like Mars? Let's not forget Lowell's canals...

Cheers,

--

Durval

Obs: to complement the sketch, here are the observation details from my logbook:

Place: Niteroi, RJ, Brazil (approx. 22.9S 43.1W)

Moon: very low on the horizon, blocked by large obstruction to the E;

Wind: none

Humidity: relatively low (no condensation on mirrors or eyepieces);

Clouds: none

Equipment used: Combes 10" F/4.9 newtonian-dobsonian telescope, Eyepiece: TV Ethos SX 3.7mm.

post-36179-133877772517_thumb.jpg

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durval

durval

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Hi David,

Hello Durval,

Good observation.

Thanks! ;-)

The difference I think is because we live at different longitudes.

Really?!? This is completely anti-intuitive for me: I would have thought that (due to Mars distance from us being several orders of magnitude larger than any distance on Earth) the observer's position on Earth would have very little influence.

What was the UT of the time of observation ??

Time? Hummmrmrmr... possibly you meant "longitude" in the previous paragraph? In any case, UT was 22:20.

Cheers,

--

Durval.

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dweller25

dweller25

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Hello Durval,

I am pretty sure you observed at 22:20 local time and assuming a 4 hour time zone difference that would be 02:20UT 12th March.

If that is the case here is how Mars would have looked from your location....

post-13701-133877772801_thumb.jpg

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durval

durval

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Hi David,

Hello Durval,

I am pretty sure you observed at 22:20 local time and assuming a 4 hour time zone difference that would be 02:20UT 12th March.

You are correct, it was local time, but I'm in the GMT-3 timezone, so 22:20 Local Time (GMT-3 timezone) 11th March ==> 01:20UT 12th March.

Hello Durval,

If that is the case here is how Mars would have looked from your location....

Did you use a planetarium program to produce that image? Which one?

I just checked Stellarium (0.11.0, for the record) and it produced a very similar image (see below) to what I saw at the eyepiece when I used both ^V and ^H to match the vertical and horizontal axis inversion done by my newtonian telescope; without that "newtonian inversion", this image is also very similar to the one you just posted. The main difference is that the white icecap is in the WRONG pole in regards to the foot-like dark area orientation...

My best explanation for this incongruity is that I did not see the north polar cap (maybe due to the bad seeing), and mistook the lighter area in the south (just under the "sole" of the "foot") for a south polar cap... What do you think?

BTW, what's your location?

Cheers,

--

Durval.

post-36179-133877773097_thumb.jpg

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dweller25

dweller25

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Hello Durval, I am in the UK.

By coincidence when I viewed Mars last night it was showing the same face as you viewed on the 11th.

I can see your confusion - the southern polar region was just as white as the North polar cap !!

Hope that helps,

David.

PS - the large dark feature you saw is Syrtis Major

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durval

durval

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Hello David,

PS - the large dark feature you saw is Syrtis Major

I had previously searched for but could not find an online Mars map which could identify that feature, but with that info I managed to find that one:

http://toolserver.org/~geohack/geohack.php?pagename=Syrtis_Major_Planum&params=8.4_N_69.5_E_globe:mars_type:mountain

Thanks for the pointer!

Cheers,

--

Durval.

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durval

durval

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Hi David,

I can see your confusion - the southern polar region was just as white as the North polar cap !!

Oliveira, a colleague from NGC-51 (local astronomy group), reported seeing the two caps the night before last night (ie, May 11th)... according to another colleague (Sergio), just the North cap should have been visible and even it should have been tenuous, due to Mars being currently in "high summer"...

So, is it an illusion or not? For me, the fact that two very different observers are able to see the same thing unbecknowst to one another indicates that, contrary to the theory, the two caps are equally proeminent right now...

Cheers,

--

Durval.

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durval

durval

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Hi Dave,

Just to be clear....

The North polar cap can be seen.

The south polar cap cannot be seen BUT the southern polar region is very bright - almost white.

How do you know it's not the polar cap? Because it's not as white as it should?

I'm not doubting you, just curious...

Cheers,

--

Durval.

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