Filament ejects

After some puzzling early convolutions and a lengthly pause between +7m and +27, this filament rushed to a  height of 136Mm, a further 70Mm in 6 minutes, about 200km/s. This is a fairly typical ejection velocity, but solar escape velocity is over 600km/s. Having reached that height it rapidly fell back to its start point. After peak height it lost much of its earlier brightess - it was about 50% chromospheric brightness at peak height.

James Dunlop and early Australian Astronomy

"Jamie" Dunlop was the first to catalogue southern "deep sky" objects, ie stars clusters and nebulae - if we don't count Lacaille who mapped some with a tiny half inch telescope! Dunlop used a home-made 9 inch reflector. It's not hard to show he was a superb observer and draughtsman, and his catalogue of 600 southern objects mapped and described in seven months (in 1826) is an extraordinary feat! But why are half of these objects now "missing"?

ASNSW has honoured me with a invitation to deliver a talk: "Dunlop the Draughtsman",  in July, when this and other questions will be discussed. Tracking down "missing" Dunlop objects is an exciting project for amateur astronomers.

The image compares well-known southern galaxy N4945 with Dunlop's sketch of it from almost 200 years earlier - and 4945 is not a bright galaxy! Background image courtesy Johannes Schedler, Panther Observatory.

2012 Transit Of Venus

Transit of Venus: Sydney. Strong cold wings and heavy cloud confronted Sydney Transit watchers this morning, June 6. Add sudden squalls of rain and there was only one option: the old soviet-era 4" F10 Maksutov (MTO). On a rugged alt-az mount it is little affected by wind gusts.  This, plus a cross-hair e.p. giving magnification 80 managed to capture 25 or so transit chords across the sun - each locating Venus at various stages of the event. I'm hopeful that when these are plotted the rate of Venus' transit can be calculated, and contacts 1, 2, 3 and 4 found (here's hoping). Unlike the 2004 TOV the 2012 contacts were not well observed through the cloud and rain (Contact 4 not at all). For a devoted sunwatcher the sight of the big black orb on the sun's disc with the current rather wispy spots made for a breathtaking sight. Venus seemed much darker than even the strongest umbrae of AR's 11493 or 11494. Amazing day!

AR11476 Returns!

AR11476 Returns! A great sunspot group is the product of a much larger region of magnetic polarity - called by some :"activity nests". While sunspots arise only where emerging fields exceed ~1500 gauss and are fairly small, the whole region or "nest" can be huge, ten times larger than the spots. Here we see (SDO EUV 304A) the region that produced 11476 a month ago returning at the sun's NE limb. There are spots here, not seen as the nest saturates the SDO detector. White light will show them well. In the corona above the site there's lots to see: PFL are post flare loops above a sunspot and surges or filaments hover above. As well a large coronal hole has developed 30 deg west of the site (black arrows). Is it involved with the "nest" in any way? How long will the nest last - what will it produce during this transit?
"Activity Nest" is a useful term used by Schrijver and Zwaan in "Solar and Stellar Magnetic Activity" Cambridge Uni. 2008. P142~