Telescope Reviews: Great night with Jupiter + Europa/Ganymede Transit

It was humid, but given all the rain here in the SE in the past couple of weeks, finding a night that was clear seemed like Nirvana! I was looking at Jupiter in my NP-127 and noticed a moon on either side, not that interesting... but then suddenly noticed a little 'pimple' on one side as a moon (Callisto) just exited after transiting Jupiter. That prompted me to look at SN to see if anything else was going on and that's when I realized that a treat was in store.

First, about 40 minutes later, I could see Europa's shadow on the surface of Jupiter - a tiny, sharp black dot entering from the other side. After a while, during steady seeing I was also able to catch Europa itself just before it concluded its transit across Jupiter. It was a bit tougher because it was between the two main belts and so did not have as much contrast as would otherwise be the case.

At that point, the humidity was climbing fast - already at 88% and rising - and being a Sunday night, my observing friends had to leave around 11pm and we packed up everything. But the real treat was still ahead.

After they left, I took my 70mm ED Scope out with a 2.5T5 Nagler (168x) and 2-4mm Nagler (210x at 2mm) to look again at Jupiter and watch the wonderful transit of Europa across Ganymede. RH was already 91%, so I was expecting it to start fogging over shortly, but it stayed clear for the next hour.

First I was quite surprised to see that I could catch Europa's shadow in my 70mm scope - a nice tiny black dot - not bad considering that Europa (by my rough calculation is no more than around 0.9 arc seconds(). Not as easy as seeing it in the NP127, but neither did it take any averted imagination!

But the real treat was watching Europa head for that transit across Ganymede. I was able to see it elongated down to within 2 minutes of the central point of the transit which took place right around 11:40pm EST. At that moment, there was just one "moon" visible. The elongation started to reappear just 2 minutes after that - so it only took about 4 minutes for Europa to cross over Ganymede. As it was exiting, the instant the elongation stretched into 2 separate moons, I rushed back to see what SN was saying about the separation at that moment - listed it at 1.5 arc-seconds. It's the first time I've ever seen a moon transiting another moon like that. And even in the 70mm scope, the difference in size between Europa and the much larger Ganymede was very obvious. That little SV70mm ED Scope never fails to surprise me with the quality of its views.

By 12:30am, I looked out and there was not a star in the sky and the RH was about 94%. All in all a fine show by Jupiter this past Sunday night!

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