Hi all! Have you seen enough photos of the Blood-moon yet? Yes? Well now that you’re here, just admire how similar this one is to all the others you’ve seen. Except that maybe the bright part is near the bottom because this was taken from the southern hemisphere. Continue reading
It was a bit of a mixed bag on Monday night with the moon passing in front of Jupiter.
I first went out for look while twilight was just kicking in. The moon was at its highest point in the sky, almost due north and not very high. Jupiter was barely visible to the east (right) of the moon. As the sky darkened Jupiter shone more brightly, becoming easily visible beside our nearest neighbour, slowly closing in.
I recalled studying the diagram in this post where I said Jupiter would disappear behind the lower right hand side of the moon. I assumed the terminator (day-night line) would be vertical. Jupiter seemed to be lined up almost exactly with the centre of the moon’s terminator. Chalk it up to a small and difficult to read section of the diagram. And me not quite knowing what I was doing!
As the hour of action drew closer I noticed Jupiter was dropping in the sky relative to the moon. But if anyone was using what I wrote last week as a guide to finding Jupiter they should have had no trouble. It was so bright you couldn’t miss it, even when it came close to the moon’s night side. I was snapping pics every few minutes with my DSLR and its standard 55 mm lens. Here’s an animation I put together of frames spanning the 35 minutes leading up to occultation, plus a bit more.
Each frame is roughly 3 minutes apart except the last few where the moon darkens. These were taken about 15 and 20 minutes after Jupiter disappeared. The darkening was caused by smoke from a grass fire north of Melbourne hanging on the western horizon, effectively occulting the moon just as Jupiter was scheduled to emerge from behind the moon 40 minutes after the beginning of occultation.
So a beautifully clear 35 degree day that promised perfect conditions for viewing the occultation, ended in disappointment for those of us in the east who, instead of seeing the end of occultation with the re-emerging Jupiter, witnessed a Lunar occultation of a different kind: that of the moon completely obscured by grass fire smoke.
It’s a big week in astronomy. You’ve no doubt heard about the meteor lighting up the Russian sky earlier today. And in a few hours time a 50 metre wide asteroid will be closer to us that some of our geostationary satellites. It will be 4:30 AM here. I won’t be watching it because I can’t find my binoculars and it’s too dim and fast-moving to be easy to find with the naked eye. Never mind.
Anyway, the original purpose of this post was to talk about a disappearance. In January I noticed the moon passing suspiciously close to Jupiter in the sky and wondered when was the last time I paid any attention to lunar occultations – when the moon passes in front of a planet or a star or something interesting other than the sun (because that’s known as a solar eclipse and is orders of magnitude more spectacular).
As it turns out from Melbourne, Australia on the Monday 18th of February the moon will in fact pass in front of Jupiter, briefly winking it out of view for about 40 minutes or so. Check out this confusing diagram (or click it to get the original at the Astronomy Almanac Online!):
The diagram shows the shadow of the moon cast by Jupiter on the Earth at ten minute intervals from start of occultation in the Indian Ocean (marked by the tiny red shadow) to the end, about 3 hours later in Tasmania at the other red shadow.
Now, assuming I interpret this diagram correctly, Melbourne will be near the top of the Lunar shadow, so from here Jupiter will be seen to disappear behind the night side near the north end of the first quarter moon. Look at the bottom right of the moon when gazing up towards the moon in the north western sky from Victoria . This will be the most dramatic part visible. It will be much easier to see the bright planet vanish behind the unlit half of the moon’s disc than trying to watch it reappear in the glare of the moon’ day side.
In fact the flat side of those half-oval shapes is the moon-set line across the Earth so Tasmanians will see the moon set just as Jupiter emerges from behind it, about 70 minutes after it disappeared.
When can you see this you may ask? Well, from the above diagram it’s difficult to get an accurate estimate but working backwards from the last shadow in Tasmania at 13:13 UT (00:13 19 Feb) The shadow will be over Melbourne between 12:23 UT (23:23 AEDT) and just after local midnight. But I don’t guarantee anything in case I read the diagram incorrectly. The moon will be on its way down in the west so it is recommended to have a clear view of the western and north western horizon.
Hope the skies are clear on the night and enjoy seeing our humble little moon obscure the mightiest planet in our solar system. Adelaide and Perth will see it too, just earlier in the evening than Victoria.
Take that 2012 DA 14!