Saturday, January 24, 2015

Jupiter Triple Transit

Last night was the publicized "triple transit" where the shadow of three Galilean moons were visible simultaneously on the surface of Jupiter. In this case, Io and Callisto crossed first and finally Europa. What a stroke of fortune that all of the recent rain and overcast skies cleared for the show ... today it is overcast once again. As usual, seeing was not very good at my site but did improve between first test shots at 23:00 and beginning of the triple at 00:28.

I created the image using a movie with about 2000 frames taken on 2015-01-24 at 00:38 CST. The movie was captured on a Canon 60Da using its handy VGA Movie Crop mode that gives a 1:1 pixel ratio image (no compression, no downsampling) at 60 fps. I connected the camera through a Televue 5x Barlow to a TMB-130ss refactor giving an effective focal length of 4550mm. Since the camera generated a MOV file, I extracted the individual frames to BMP images using IrfanView 4.36 and then imported them into RegiStax 6 for alignment, stacking, wavelet sharpening and color alignment. I imported this processed image into Photoshop CS6 and further tweaked the saturation, contrast, and brightness as well as adding labels. The moon and shadow positions shown were identified from a simulated view in SkyTools 3.

Given the quality of the raw movie frames, I am surprised that I was able to extract recognizable images of not only the shadows but also of the moons that caused them. The disk of Io was particularly challenging and shows up subtly as a yellower disk region. I was not able to see this disk in any single raw frame. The body of Callisto looks like another shadow as it is the darkest of the principal moons.

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