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Mars 4 february 2010

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#1 Jef De Wit

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Posted 05 February 2010 - 05:16 AM

Yesterday I looked with some members of my local astroclub at Mars. There were two 12 cm refractors (one APO and one semi-APO) in the company. I allways thaught that these telescopes were excellent for planetwork because they have no obstruction. But the view in my 12" won the competition!

It was the first time I looked for a second time the same region of Mars. Compared with an observation of the 1st of january Hellas was very difficult to see. One month ago it was very bright.
This time I also noticed almost no limb haze. There was only I brighter region at the northwest of Mars (or was it Mare Acidalium rolling in?).
Mare Serpentis and Sinus Sabeus looked like a half-ring on the southwest. Beautiful sight!
Another strange thing is the position of Syrtis Major. I see it in the eyepiece far south (it doesn't cross the "middle" of Mars). In simmulations of Mars it comes far more north.

All comments are wellcome!

4/2/2010, 21.00 UT, CM=300°, 12" dobson @ x300, apodizing mask

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#2 Uwe Pilz

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Posted 05 February 2010 - 06:37 AM

It is important really to sketch what we see. The visual impresion of a planet may be differ serios from photographs.

My sketch one day ago an with a similar CM shows Syrtis maior in a position comparable to your sketch. The "half ring" of the mare serpentis I saw far less contrasty. Interesting.

#3 Kris.

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Posted 05 February 2010 - 07:50 AM

good sketch Jef. about the position of Syrtis Major: i think it may have something to do with us, telescopic observers, being limited to seeing only the major outlines of the northern tip of S.M. when you look at some photo's the tip becomes less and less 'pointy' and 'bent' the more detailed the photo becomes (aperture, resolution, good seeing and good processing techniques?) so there's more to see in pictures than (most) sketches, which could be why on photos S.M. may seem to extend further North...

take a look at this nice image from pete lawrence in the solar system forum: link notice how the B&W version seems to show a shorter S.M. than the colour version. perhaps because it masks finer detail around the area. the colour version shows the bended hook at the tip of S.M. embedded in more, finer detail, which i can't resolve with my eyes & scope, so my sketches of this region, as well as other people's sketches, show the tip with a hook.

this is just an idea of mine though.

how's your colour technique developing btw?

#4 Jef De Wit

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Posted 05 February 2010 - 09:48 AM

@ Uwe
I agree, it is very important that you sketch what you see, but I like allways - when the sketch is finished - to put a planetariumprogram or a photo next to the sketch.
I looked at your sketch from the 3th and you saw Hellas really bright. Strange.
About the half ring: our brains look for structure. So maybe once you think you saw a structure, you will see it again and pay attention to it and sketch it maybe to expressive.

@ Kris
Thanks for the theory. About the colour. My previous sketch I started with yellow all over the planet (except the polecap). Then added orange (except on the cap and the yellow-regions) and in the last step brown. For this sketch I didn't worked with layers and set every region directly in his own colour. I don't know what works best for me... still experimenting.

#5 frank5817

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Posted 05 February 2010 - 11:27 AM

Jef,

This is an excellent sketch. I agree with both Uwe and Kris.
There are those times when the atmosphere cooperates and you can see an amazing amount of detail, but those times don't occur but rarely. :bow: :rainbow:

Frank :)

#6 niteskystargazer

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Posted 05 February 2010 - 12:27 PM

Jef,

:waytogo:, nice sketch :).

:thanx:,

Tom

#7 Jef De Wit

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Posted 05 February 2010 - 01:14 PM

Tom, Frank, thanks for the kind words.

#8 mathteacher

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Posted 05 February 2010 - 02:25 PM

I like your color sketch! I wish we had some clear skies right now. Congratulations on beating the apos.

#9 Tommy5

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Posted 05 February 2010 - 05:59 PM

very nice Mars sketch, with the north hemisphere of Mars facing us, Syrtis Major can be foreshadowed into a similar position as your sketch, thanks for posting.

#10 Special Ed

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Posted 06 February 2010 - 10:40 AM

Jef,

Well done observational sketch--it's important to sketch what you see how you see it. You noticed changes from your last observation--that's why Mars is such a great target. Clouds, ice, dust all moving and changing.

Tommy's right about the effect of foreshortening. We are currently seeing much more of the Martian northern hemisphere than the southern hemisphere. The Martian equator doesn't go through the apparent "middle" of the disk--it arcs farther to the south.

#11 Jef De Wit

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Posted 07 February 2010 - 05:20 AM

Teacher, Tommy and Michael :thanx:

#12 rerun

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Posted 07 February 2010 - 06:53 AM

Hallo Jef,

you used the some clear sky on February 4th,like I do.Great sketch of Mars with some more details,that I could see with my small scope.Thank you for sharing with us all.

CS

Markus

#13 Jef De Wit

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Posted 07 February 2010 - 08:02 AM

I made a version with labeling. It' a good excercice for knowing better Mars. I hope it's correct!

I don't know what's the name of the dark zone surrounding the polecap. I thaught it was Utopia, but the labeling of Carlos on other sketches here on CN put it more south.

Randnevel is Dutch for limbhaze.

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#14 dweller25

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Posted 07 February 2010 - 08:50 AM

Jef, great drawing, did you ever try a #21 orange filter ??

#15 Jef De Wit

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Posted 07 February 2010 - 02:44 PM

No, I have no colourfilters. I have ordered a set of 4 filters from Orion in an astroshop some 3 weeks ago. I think they will arrive when the Mars-party is over :bawling:

I once used a redfilter from someone else. It gave a little better contrast in my scope. But if you look at Mars later on without redfilter, the planet looks WHITE! And it takes some time for the eyes to come back to normal colours.

What are your experience with the orange filter?






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