Ganymede visible during transit?

[AndyWB]

I'm worried I'm asking a daft question, but I was out a bit earlier (around 2145) for a bit of a gander at the moon. I decided to look at Jupiter too, through the cloud. Conditions weren't great - the view was pretty mushy (temperate belts only just visible) - but I could only see 3 moons, and there was a darkish spot on the surface, occasionally visible in the middle, below the Southern Equatorial Belt. It wasn't the pinhole black colour of a shadow transit, so I was puzzled, and I checked JupiterMoons App. It showed Ganymede as currently transiting, and in the same location on the disk - middle, and a little south of the Southern Equatorial Belt.

Is that possible? To see Ganymede itself while it is transiting? In a 130mm scope? I didn't think it'd be visible.

[oldfruit]

Hi Andy, it is possible to see the Moons during transits. I and other members of our club have seen them on more than one occasion. The moons are usually easier to see when they are nearer to the edge of Jupiters disc due to the glare. We have watched the start of many transits, seen the moon easily in front of the planet but as time progresses it becomes increasingly difficult to follow.

This is not always the case as all observing sessions are reliant on seeing etc so some transits may be more visible than others.

[Stu]

It's certainly possible, and depends where exactly it transits I think. I've always struggled to see them, normally only picking then up at the start or finish of the transit where the darkening towards the limb allows the brightness of the moon to stand out. I guess it depends which moon too, and whether it is over a similarly coloured area of Jupiter or contrasting against the background.

Great fun to try and see though.

Cheers,

Stu

[AndyWB]

Thanks guys,

That's cool! I did not expect to be able to see a moon during transit against Jupiter's glare! I'm pretty chuffed about that!

[CSM]

Yes, Ganymede was in transit across the face of Jupiter and I did manage to capture it - see my blog on website. Not particularly good images because of the Moon.  Io should also have been there but I think it was behind Jupiter rather than in front.

[AndyWB]

Yup, that looks like it - though it's clearer in the photos.