Despite the ghastly weather, this meeting was perhaps the richest yet in terms of visual treats.
Greg Priestley showed several 16 mm F/L F4.5 videos of the sky at the Hunter. The Magellanic clouds, milky way, coal sack and the rest of the emu, Pleiades, Hyades, Orion were all very easily spotted. Michael Samerski noticed that M31 could be just glimpsed. Brighter stars (Pointers, etc) could be seen reflected in the surface of the lake.
Mike Berthon-Jones showed Yoda's Walking Stick, and the Flea in the Pussycat's Ear (being in CrA and M20 respectively), and asked people what the difference was. Polite silence. Mike explained that in both shots we were looking at a Herbig Haro object - a bipolar jet from the exact moment when a star switched on nuclear fusion, and the escaping material was funneled out in two powerul streams because ions can't cross the magnetic field lines. That is incredibly important for getting rid of extra angular momentum, which gets squirted out as the ions spiral around the field lines. Without these bipolar jets, the star has too much angular momentum, and can't condense out of its' primordial disc without flying apart. The difference between Yoda and PussyCat is that the Walking Stick is illuminated by thermal radiation from the shock as the jets hit pre-existing material, whereas the Flea is lit from outside, fluorescing in the light of nearby type O stars. Herbig-Haro objects are to me utterly awesome because of what they signify - the moment when the star switches on. They are pretty rare, but here are two that we can all see and photograph. There are others in Orion and Carina.
Marc Aragnou produced a physically beautiful panorama of Flame to Horsehead, perhaps the nicest I've ever seen. It was a collage of many many different attempts, put together using RegiStar. Very fine effort. He also (under duress) gave an overview of his new HyperStar 3, discussing collimation issues and the correct use of a metre of 4x2 oregon, and showing one or two uncollimated first attempts which were already pretty awesome in terms of speed. Exposures of just 30 seconds produced wonders.
Mick McCulloch showed his Jupiter (best 300 frames from 1000, Crago main instrument, stacked with Registax 5 I think). It was awesome - NASA quality. To me this is just witchcraft. He also gave a guided tour of the all-sky survey plates in Grus, showing hundreds of things to photograph, within range of anywhere between a 4 inch and a Big Beast.
Geoff Smith showed 4 photos with his 4 inch (?) scope, including one very impressive globular. His helix needed more light, but was a good early effort.
Joe Cauchi showed his usual series of jaw-dropping take-that-you-blaggards shots with the 16 inch f/4.5 Newtonian. His Helix had several background galaxies visible THROUGH the helix nebulosity. His stars were so tight that you could distinguish between the hundreds of background stars, and hundreds of background Galaxies. I am very very jealous. He showed the Pavo spiral, and lots of other goodies.
Michael Samerski showed his M31 nucleus with his 8" SCT on the Modified BlancMange mount. It was very, very good. Again, it shows that even though it is very low in the sky, it's worth photographing, even at long focal length. Michael S also asked the group about whether it is better with a DSLR to shoot at 800 or 1600 ISO, if your goal is to get a less "stripy" image. Nobody had a clue, but everyone shouted out lots of advice. Dick argued for "the slower the better". I said I thought that worked if you were photographing very very bright objects, but might not apply to the extremely faint, when readout noise is the problem. Others said, "the faster the better".
This caused howls from some, who said it just increased the noise. I argued that the stripes were not shot noise, but readout noise, and thus the question was whether the ISO gain was applied before, at, or after the readout transistors. If the gain were applied BEFORE the readout transistors (assuming that is physically possible, eg by increasing electrons-per-photon quantum efficiency), then the higher the ISO the better. If it were applied AFTER, or in software, it should have no effect. If it were applied AT the readout stage, you'd need an electronic engineer to answer. Nobody knew.
Fred confirmed that the ISO rating is applied in hardware at some point, not in software to the final image, and said, "There's HUNDREDS of threads on this on Ice In Space". Much "hear, hear!" from the floor. "Well, what's the answer? What should we do?". Nobody knew. We eventually decided that (a) it was incredibly important, and (b) in lack of other knowledge, one would just have to try say 800, 1600, 3200, and see, but that my guess is that for faint objects, faster is better, because at very low ISO, you get no signal but just readout noise, and your galaxy looks like the Stars and Stripes. In Michael Samerski's case, the answer was really clear: 1600 worked MUCH MUCH better than 800, despite a shorter exposure. His NGC 253 at ISO 1600 was, in fact, quite good.
Mike Berthon-Jones ran through a few early morning galaxies - the Sculptor semi-dwarf, the beautiful pseudo-ringed 1808 and its Ugly Duckling clumpy 1792, and 11 hours of 1365. Between them Mike had marked some 280 background galaxies, giving credence to the idea that We are Not Alone. Also a shot of M4, which [Mike modestly claims] was nowhere near as impressive as Geoff's globular.
Many others contributed; the above summary does not do justice, but the details are slipping. My apologies for the dozens of omissions. We are all getting noticeably better at preparing and giving presentations, organizing material, working the projector, and keeping to time, and the quality of the images continues to amaze. Some have complained that Windows Media Player uses a very distracting white background. In Slide Show mode, this can be set to black, but not in the zoomable, pannable mode, which is absolutely necessary for exploring very large images. We will think on this. Some have also noticed that despite doubling the number of meetings, we are still having to rush, so that issues are not fully explored. Since almost all meetings are now pretty chokkers with good stuff, postponing stuff till next time won't really work, as next time is also going to be chokkers. Personally, I think having too much to show, and too much to talk about, is exactly the problem that other astro-imaging groups would die for. If people continue to rehearse their stuff on their laptop at home, we will get still faster and more organized, and more fun can be crammed into a shorter space. ON THE OTHER HAND, if anyone would like to volunteer to run a meeting or two, they are most welcome!
The 2 December meeting will be Show and Tell, followed by drinks and nibbles and yacking about the good old days when there were stars east of Broken Hill. No entry without something edible or drinkable. I'll bring some dips, crackers, and olives. I'm thinking Very Genteel and Legal rather than a Booze-Fest, as we're not set up to handle that. Everyone please bring SOMETHING (including mineral water, coke, OJ, etc), preferably of a non-spill, non-carpet-damaging variety.
Mike Berthon-Jones
ASNSW Astro-Imaging Section Leader.