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Jupiter with Io and its shadow transit, while Ganymede looks on

Technical card

Resolution: 3098x2065

Date:May 14, 2019

Time: 18:59

Frames: 40000

FPS: 53.00000

Focal length: 775

CMI: 323.60

CMII: 330.80

CMIII: 293.90

Seeing: 3

Transparency: 8

Locations: Home property, Wattle Flat, NSW, Australia

Data source: Backyard


I continued my imaging run of the 14th to capture the shadow transit of Io. Although the seeing had deteriorated somewhat, the resultant image was of reasonably good quality.
Managing the shadow is quite difficult when imaging with monochrome RGB, because the shadow obviously moves from red to green to blue. As a result across the WinJUPOS integration it is seen as a black/ grey smear. I made 9 RGB runs in total. I also integrated the central one, which had pretty much a perfect shadow, with a hint of red to one side and blue to the other....again because even over the 3 minutes of capture the shadow moved. I put the single RGB run image in a layer under the colour image from the 9 RGB run integration and using a layer mask I exposed the correct cloud colour and details underneath, thereby removing the smear. I also used a monochrome "green" image with a perfect shadow, again in a layer underneath, to clean up the shadow and mitigate the red and blue leading and trailing edges. The shadow being black allowed me to use this technique.



Niall MacNeill
License: None (All rights reserved)


Jupiter with Io and its shadow transit, while Ganymede looks on, 


            Niall MacNeill