ollypenrice

If the mods will excuse me, flat balls are inherently odd. I'm an intruding literary type in this conversation so my starting point with your students would be, 'What does bang mean?' I suspect that after three minutes' discussion the conclusion might be, 'Very little.' Any student arguing that it meant, 'Expansion from a single notional point' would be on a hiding to nothing. At this point 🤣 I'd feel in a strrong position to introduce the idea that 'Bang' was not a bad term to describe an event as yet incomprehensible but, within the limits of our present comprehension, real. Olly

The metre requires us to hear, 'Lex200,' no? Olly

I'm sure it is used by professional cosmologists. It was coined by one, after all, and I've heard several use it. Of course it's nothing more than a handy label and it does carry some baggage, as you say. I still think it carries about as little as any term can be expected to. Language itself carries quite a lot, unfortunately. The fact that we have a subject-verb-object structure so deeply embedded can try to lead us astray. We say 'It is raining,' for instance. But what is? Immediately there is a ghost in the room. Why don't we just say, 'Raining.' It's perfectly reasonable for verbs denoting the actions of sentient creatures to have subjects but there is always that lurking anthropomorphism when actions are performed by non-sentient beings. (As in that statement, for instance! 🤣) Olly

I agree. That's why I think the term Big Bang has endured. It can name what we're talking about without predisposing us to think in any particular way, including a way which involves taking a fallacious extrinsic view. (Those writing about Darwinism encounter the extreme difficulty of doing so without using terms which contradict the very points that they are trying to make. It can be hard to avoid implications of design or purpose in describing evolutionary processes. Similarly I think the debate over human and artificial intelligence is rendered almost impossible by the anthropomorphic terms in which computers are discussed. We are told that computers have 'memory,' that they search and retrieve, that they select and so on. If we use these terms then we are starting off the discussion with an innate bias. Olly

An interesting link: thanks. However, since it's about flat earth models it doesn't concern itself with spherical ones. The oldest recorded terrestrial globe dates from 150 BC and the oldest surviving one dates from 1492, predating Magellan's first circumnavigation by some thirty years. The replacement of the flat earth model with the spherical one was piecemeal and, indeed, is ongoing since there are plenty of odballs who deny the spherical Earth. It's an historical curiosity that the term 'Big Bang' was coined by a non-believer, steady state theorist Fred Hoyle and, quite possibly, was coined off the cuff. I think Andrew has pointed us in the direction of understanding why such an unscientific, even facetious, term has taken irrevocable hold. Being the loosest kind of metaphor imaginable it carries no baggage of preconceptions. It is an empty noise, if you like, and so a perfect label for something not conceivable in normal terms. It won't lead you astray because, as a term, it doesn't lead anybody anywhere. I suspect that's why it has stuck. Olly

Stockhausen's gearchange. Olly

Who thought the earth was flat and when did they think it? Do you know? Does anyone? This isn't science, it's history. Given that, in the past, communication over large distances was difficult, many communities did not write down their beliefs and that history is a long time, there will have been many beliefs and many changes in belief, few of them recorded. The throwaway notion that 'we used to think the earth was flat' is a careless assumption and demonstrably false. People had seen the earth's curved shadow cast upon the moon during an eclipse. They had seen receding masts set below the horizon. They had seen the constellations change when you traveled north or south but not when you traveled east or west. More subtly, in a way, Polynesian navigators managed to pass between islands using a knowledge which still eludes modern comprehension. So, with respect, when you say, 'The human race is just making up what it thinks happened because that's what we do.....' that is, in fact, exactly what you are doing. You are making up history. All the great European navigators - Magellan, Columbus and the rest, knew that the earth was (roughly) spherical. No educated person needed proof of this by the time a circumnavigation did prove it. Olly

What do people think of the various hologram/simulation hypotheses? Personally I find them predictable and fatuous. They're predictable because they are just what you'd expect bright people who play too many video games to come up with. They're fatuous because they are not falsifiable in principle, because they throw us into an infinite regression (who made those who made the simulation?) and because they are utterly anthropomorphic. I would far rather spend my time thinking about the implications of what fragments of reality we see being selected and edited into a narrative by the ways in which we see them. Olly

That makes sense. With an alignment device you could also frame the two pictures independently to overlap exactly where you wanted to - but be aware that this would be time consuming in reality. It looks simple enough but precise control of alignment is a fiddle even with the Cassady T-GAD. Olly

Do you actually need to have the two scopes perfectly aligned? If so, why? Olly

Yes, we're in blend-land with these techniques! Left a bit, right a bit... Ten minutes later it's, What was I thinking??? 🤣lly

Deleted - I misread a post.

They're the same stars but, yes, an artefact has crept in. I hadn't noticed, but it isn't present in the TIFF. Ideally I'd not replace the reduced stars, as I did here, but go back to the pure RGB stars and apply those. I'll have a trawl through the old data and see if I can make that work. Olly

My stepson Sasha, an IT professional, took about 10 seconds to get Starnet++ working in PI after I'd spent an eternity failing. (It' s a star removal routine.) I've now tried three ways of removing stars, my own simple one, Straton and Starnet. Starnet wins and is free and 'one click' to use. Narrowband imagers wanting to remove stars entirely will want a perfect result. I don't need that because some residual starry presence will be covered when I replace the stars with less stretched ones in my broadband images. Below is the 'Gamma Cass and Breaking Wave to Pacman' image Tom and I did a while ago. On the left the stars are as small as I could get them without using the 'remove and replace' method. On the right is the result of removing them with Starnet, giving the nebulosity one tiny extra push, and then replacing the left hand image's stars at partial opacity. Honest preferences: what's your feeling?

A resounding Yes to this. Although 'hiding it from the other half' is a kind of running joke on SGL, there was a touching and deeply disturbing post from a member who deeply regretted doing this because it damaged a precious relationship. Hobbies (not my favourite word) take us into worlds of specialized equipment made in small volumes, so an expensive world. We make our peace with this world as we each see fit. It's easy for me: I make a living with my kit, all of which has high residual value. And it's also easy because if I pop my clogs tonight I know that our 'regulars' and robotic clients will see Monique gets a fair deal out of what's left. I don't need to verify this beforehand, I know it. Olly

My golden astro rule is, 'If it ain't broke don't fix it,' so I actively dislike introducing new kit. Of course, this is partly because the kit I have is very good. What I really like doing is going out and using it in the knowledge that I understand it and that it will almost certainly work. This might seem surprising but I'm not really all that interested in kit. Above all I just want it to work. Anyway, by far the most important thing to have is a good sky. Olly

It might be worth saying that astrophotography has reached its present standard because people have been prepared to experiment and go against the received wisdom. But, sure, some initial pointers are helpful. Don't let this stop you from experimenting, though. I've been told plenty of times that I shouldn't be using 30 minute subs with a CCD camera. Still use 'em, though! Olly

Oh no! There's a famous historical novel (The Murdered House) set near to my place, in which the villains do away with a wealthy enemy by soaping the path round his ornamental pond on a winter Friday. They chose Friday because, in winter, his housekeeper always gave him pieds et paquets, an incredibly rich offal dish, that evening. To slip into cold water after such a meal would be - and was - fatal. Watch what you eat on imaging nights, Gina! 😮lly

In terms of the view the biggest difference, for me, would be in field of view. I find myself boxed in by long focal lengths, particularly when the aperture is modest. Olly

My concern as well. The eagle has vanished! I think the Swan, though, is the object most like its name at the EP, especially if you rotate the diagonal to get the water level. Olly

🤣 Hey, I do all this in PI nowadays, before fleeing to the sanity of Photoshop. But I used to do it pretty much as you descirbe. I make a point of not commenting on peoples's buts on SGL: I certainly don't want them commenting on mine! Olly

I was about to say something so similar as not to be worth the distinction. Olly

It's a big issue. Small stars give an image the 'big telescope' look. Olly

Good call, Ciaran. Thanks. I'd been playing around with the 'something odd' I could see in the background but hadn't twigged that it came from the blue channel. With the blue brought down the non-Ha dust has come up and there's a more natural interaction between the dust and the gas. I owe you a pint, Sir! Olly

No. In my case the top layer containing the stars is not added at full opacity in blend mode lighten. That's where the reduction comes from. The cores of the stars are their brightest parts so they are the first parts to appear in BM Lighten. At partial opacity they are the only parts to appear in the blended image, which is why they are smaller. Once flattened at the chosen opacity I might well paste this star-reduced new version over the original to check my judgement. If I've over done the reduction I can reduce the opacity of the reduced one over the original. I can also remove from the top layer any brighter stars which have been damaged by the reduction process. (A quick dab with the eraser takes care of it.) Olly Edit: I didn't do it this time but another bright idea might be to paste the RGB-only on top of the starless HaLRGB since the RGB stars will be smaller and have unadulterated colour, possibly more intense. Something to try next time!