Observing Saturn

 
Digital airbrush painting of Saturn from an observation made on
06OCT2001 04h:00m to 05h:00m UTC Seeing I-II Conditions:T5 Moon
10.25-inch f/10.6 Spec x457 6mm Zeiss Abbe Orthoscopic

DRAWING SATURN

The tilt of Saturn's ring system varies over a range of 0 to 28 degrees in a period of 7 to 8 years (one quarter of Saturn's synodic period). Drawing the ring system by hand calls for the draughting and cutting of a stencil. However drawing the outline in a CAD package is much more straightforward. Once the outline has been prepared it can be exported as either a vector or bitmap into a graphics package and used for preparation of a template painting.

I have drawn outlines for tilt angles at one degree intervals, and also included the approximate equatorial limit of the NEB & SEB as a guide.

DIMENSIONED GENERIC SATURN TEMPLATE.pdf

Choose your template

 1_deg TEMPLATE

  5_deg TEMPLATE

 9_deg TEMPLATE

  13_deg TEMPLATE

 17_deg TEMPLATE

 21_deg TEMPLATE

 25_deg TEMPLATE

  2_deg TEMPLATE

  6_deg TEMPLATE

  10_deg TEMPLATE

  14_deg TEMPLATE

 18_deg TEMPLATE

 22_deg TEMPLATE

 26_deg TEMPLATE

  3_deg TEMPLATE

  7_deg TEMPLATE

  11_deg TEMPLATE

 15_deg TEMPLATE

 19_deg TEMPLATE

 23_deg TEMPLATE

 27_deg TEMPLATE

  4_deg TEMPLATE

  8_deg TEMPLATE

  12_deg TEMPLATE

 16_deg TEMPLATE

 20_deg TEMPLATE

 24_deg TEMPLATE

 28_deg TEMPLATE

Trimming ellipses in most CAD packages is awkward. It isn't actually necessary to do so, because once the file is exported into the graphics application the portion of the ellipses that are hidden can be erased.

The technique I adopt, because only one or two templates are needed for each apparition, is to prepare a generic airbrush painting, without shadows. The saved paint template can then be used as the basis for an actual observation, globe, ring and shadow details being added, modified &c to suit. The observed sharpness of the image can also be manipulated by using a smoothing deconvolution, until a close match is obtained.

I normally export the vector file as a bitmapped Mac pict @ 1200dpi, and prepare the painting template as a 600dpi 16bit depth tiff. The resulting file size for a 4inch major axis to ring A, and a 5" x 3".25 background, is about 40Mb. The completed painting can be printed onto gloss card. I use QuickTime for the colour conversions. Another suitable colour control programme is Pantone.

The file can be converted to 24bit @ 72dpi and compressed by a factor of 100 and saved as a jpeg suitable for e-mailing. The resulting file size compressed is then about 30kB, expanding on opening to 3Mb.

You do not need an especially powerful PC to do this type of work. I use an old 7300-166 PowerMac with 160Mb DIMMRAM; CADintosh v4.1.2; Graphic Converter v 4.0 and Microfrontier Enhance v 4.0. Although producing the airbrush paint template is tedious and time consuming, it is not difficult. You will find it a great deal easier however if you have a graphics tablet and either a cordless wand or a cursor.

The dimensioned drawing shows the relative radii of the rings compared to the globe's equatorial radius. The minor axis of the globe is given for B values at 7 degree intervals. The minor axis of the rings can be found by multiplying their respective major axes by the sine of the tilt angle.

For other planet oultines download Winoutln.exe

Top of Page



AFTER ALL THESE YEARS WHY DON'T THE BAA HAVE USEFUL SATURN TEMPLATES


Back to Home Page