Friday, January 20, 2017

Transit of Io in Jupiter

There are times when the atmosphere allows one to use high magnification and that´s when  one can get the best view of the planets. One of those times I looked at Jupiter, I got lucky that the seeing was good because I could not only see some of the gas giant´s surface details, but also one of it´s moons in transit: Io, the innermost of the four largest moons and also one of the lovers of Zeus (Jupiter).

Click on the image 
Io was having an encounter face to face with Jupiter (she does that all the time) and I could see her shadow just sticking out from the edge of one the two brownish bands of the planet. Since it was my first transit I decided it was an ocassion to sketch and also a way to show others how Jupiter can be seen through a 6” SCT scope.

Until now, I haven’t felt the need to use filters for planetary observation, but some weeks ago I discovered that fogging up of the eyepiece (with my own breath) dismished the planet’s brightness and helped some subtle details to stand out.

The original sketch does not show the true size of the planet, compared with the FOV, that theorically should be of 21 Arc minutes using the 9mm Celestron X-Cel eyepiece.

One of the reason I did not sketch a scale size planet is because it does look small despite the 166x of magnification but somehow one learns how to get details inside that little ball of light. This is definitely a learned skill that develops with more time looking through the eyepiece.

Later on, I decided to process the sketch and add some color trying to simulate the true view through the eyepiece. I felt happy with the results so  I decided to simulate the view in the eyepiece and for that purpose I used Stellarium to guide me in scale.  

Callisto, another of the largest four galilean moons was in the scene according Stellarium so I added it digitally to the sketch.  

I enlarged the previous images considerable to show more detail. Please click on the images to see their real size. With this, I hope I would cover some of the questions about planetary observation and magnification.

Clear skies,


Edited by Jennifer Steinberg (editor in chief).

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