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Saturn in mid-March 2009

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#1 frank5817

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Posted 15 March 2009 - 02:02 AM

Saturn in mid-March 2009

With the rings nearly edge-on but opening just slightly, I felt it was time to record another sketch of the ringed giant. To begin the sketch I used a white Conte' crayon and compass to draw a circle on black paper. I then used a mechanical drawing tool called a French curve to convert the circle into an ellipse after plotting a few points to create an equatorial bulge. When the shape looked alright for the bulging globe, I sketched the rings and then the globe while looking through a 4 mm orthoscopic eyepiece (magnification 362 x).
I observed Saturn for 40 minutes before beginning the sketch which took about 50 minutes to complete. I made note of the positions of the moons I could see and added Tethys (10.3) and Rhea (9.9) to the west of the planet and Dione (10.6) to the east. Titan was well beyond the planet to the west and Iapetus was visible above the planet to the south. Both of these moons were beyond the boundaries of the sketching area. The planets equatorial zone and the north and south temperate zones were bright and distinct. The darker regions over the remainder of the disk were less distinct through the polarizing filter I was using.
Although the transparency was only average at 3/5, the seeing however was exceptional at Pickering 8.5. The stars were rock steady for long intervals.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper, 6”x 16”, and white and black Conte’pastel pencils and Conte' crayons. The globe of Saturn is about 2.5” inches in diameter. Brightness was slightly decreased (-3) and contrast increased (+3) after capturing the sketch using a digital camera.

Telescope: 10 inch f/5.7 Dobsonian and 4mm eyepiece 362x, single polarizing filter
Date: 3-15-2009 4:20 – 5:10 UT
Temperature: 0°C (32°F)
clear, calm
Seeing: Pickering 8.5


Frank McCabe :)

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#2 markseibold

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Posted 15 March 2009 - 05:42 AM

Frank

Beautiful sketch. :bow: :bow: :bow:
I too purchased a set of French curve drafting templates recently but have never figured exactly how to employ them for Saturn’s planetary bulge or the rings. Can you describe how you plotted the drawing points to utilize the French curve?

Thanks again for posting,

Mark

#3 CarlosEH

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Posted 15 March 2009 - 07:59 AM

Frank,

An excellent observation and report of Saturn. I am glad that you enjoyed a nice view of the ringed planet and it's satellites. The use of the French Curves is a good way of reproducing the rings. Thank you for sharing it with us all.

Carlos

#4 frank5817

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Posted 15 March 2009 - 01:14 PM

Mark and Carlos,

Thank you both for your kind remarks.:thanx:
------
Mark,
I have attached 4 images of how I used the French curve tool. I made the sketch above on black paper but to demonstrate what I did it is easier to see on white paper.
First I found the center of the paper and drew an equatorial line and marked a center point. The circle here was made using a transparent cup (fig.I).
Second I plotted the new radius (or diameter)along the eq. line. The radius out to the equator is 5.25 percent larger than out to the pole. For this sketch that works out to 4mm larger on each side of the equator in this current drawing. Using the French curve I plotted points from the new equator back to the poles (fig.II & III). The ellipse shape is a little crude but as you know Conte' crayon erases easily (fig.IV). I did the rings free hand and that is very easy when they are nearly edge on and have a center line.
To help me with the rings, I did use the French curve like an eraser shield. I hope this makes sense to you.

Frank :)

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#5 Tommy5

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Posted 15 March 2009 - 02:19 PM

Great sketch of Saturn, brillant use of French curves, i usually use one of Sol's templates for saturn, i will have to make time, to observe and sketch saturn as the weather warms and the planet is well placed for evening viewing,.

#6 JayinUT

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Posted 15 March 2009 - 04:58 PM

Frank,

Excellent sketch and thanks for sharing how you used the French curves.

#7 frank5817

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Posted 15 March 2009 - 05:44 PM

Tommy5 and Jay,

Thank you both gentlemen, I was so impressed with the view I felt pushed into sketching Saturn.:thanx:
I would use Sol's template too but I didn't want to lose sketching time while I went looking for it. This was not a planned sketch. I did spend time trying to get a look at Hyperion which was out beyond Titan. I was unsuccessful but I don't understand why, I have seen it before in a similar position.
It has been several years since I got such a good look at Saturn - Very good seeing.

Frank :)

#8 rolandlinda3

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Posted 15 March 2009 - 06:41 PM

Very nice Frank and thanks for the helpful lesson also. Are you on a platform...at 320X, if you are not, you must be fast at chasing the planet through the sky! Roland

#9 frank5817

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Posted 15 March 2009 - 07:46 PM

Roland,

Thank you for the compliment. Yes, I always sketch using an equatorial platform for tracking. When Sam Johnson first announced that he was going to build cast aluminum equatorial platforms I signed up to buy one of the prototypes for $450. It works beautifully. It is easy to use and runs on DC AA batteries or on AC. I bought another for the local community college where I do monthly open viewing for the public once per month in good weather. The platform tracks very well for about 45 minutes and is easy to reset in seconds. I have heard they are no longer made which is too bad.

Frank :)

#10 markseibold

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Posted 16 March 2009 - 02:51 AM

Frank

Thanks again for posting your French Curve technique. I used Sol's template for earlier Saturn sketches due to ease of tracing it while I was fatigued at sketching. I'll remember your method now in case of a need in the future.
Thanks for posting the tutorial photos as I believe that these painstaking instructionals always serve to inspire new sketchers to understand that artists will sometimes employ many exerted efforts to achieve great sketching art.

Mark

#11 Tom Machtemes

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Posted 16 March 2009 - 10:31 AM

Frank,

Nice sketch of saturn. :cool:

We'll see it on March 27 :question:

:thanx:

Tom

#12 frank5817

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Posted 16 March 2009 - 10:50 AM

Mark and Tom,

Thank you.:thanx:
---
Mark,

I used the mechanical drawing tool to get the planet shape close to correct. I think just drawing a circle would work well enough and if you are being really precise Sol's templates are the way to go.
---

Tom,

Think clear skies for the next 11 days.

Frank :)






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