In search of sharp limbs...


    ISSUE: Would like to get Starry Night's opinion about to-the-second limb contact times for next June's transit of Venus. 

    PROBLEM. Edges of both the Sun and Venus need to be sharp for this, and while Keiron showed me a simple way to get Venus to sharpen up (maximize brightness on the dark side slider) I still can't get the sun to resolve as a sharp-edged disk. (No offense to the programmers--I do understand the need to categorize the sun as a planet in SN--but not with no way to disable limb darkening. Come on folks, a limb-darkened star is patently unnatural.)

    NOT REALLY A SOLUTION, BUT STILL. Here's my very jerry-rigged semi-solution. I'm running Mac OS 10.7.2 on a Mac Book Pro, and when I hit command-shift-4 to snap a selected-area screen shot of the limb-darkened sun I noticed that as you drag the screen shot capture box over the darkened edge, it sharpens up beautifully. This sharpening lasts only as long as the capture box is active however; The moment you release the mouse button to capture the screen shot the limb in the image reverts to darkened/fuzzy. (NOTE: this effect works when snapping screenshots of screenshots, so it is not caused by an interaction with the Starry Night program.)

    ACTUALLY, MORE OF A SOLUTION THAN I'D LIKE TO ADMIT: If you hold the mouse button down with the capture box active, the sharpened limb is maintained as time passes in Starry Night, so mission accomplished; I can get transit contact times to the second.

    REFINEMENTS. To avoid having a desktop peppered with worthless screen shot files, I now use the "Copy Screen Shot To Clipboard" command which is command-control-shift-4. Requires dexterity!

    I'll be looking for that "sun limb-darkening disabling" feature in some not-too-distant SN update!


    Steve Russillo

    High Point, NC