ollypenrice

Not sure I agree with this. It is possible to envisage the existence of something without knowing what it is. 'I cannot imagine what made that noise outside.' Language allows us to hypothesize the unknown. You're the mathematician, but doesn't mathematics do the same? Are there not formal proofs of the unknowable nature of a term? Olly

Though I haven't read it, Fred Hoyle wrote a SciFi story about a sentient cloud, I think. Olly

Given that we have learned to use technology to probe regions inaccessible to our senses, would it not be possible, in principle, for beings to evolve so as to do so without the technology and perceive these regions directly? Our technology involves the use of the same atoms and molecules, the same energy sources (ultimately solar) and the same underlying physics. We know that we are surrounded by an assortment of what physics calls fields and can detect them technologically. It's a small step to think of detecting them directly - provided we stop thinking anthropomorphically. A step further: the quantum world remains, in many ways, closed to us. We have made remarkable discoveries about the way it will behave given different stimulii but we can't grasp it intellectually in the way we can a billiard table during a game, for instance. If we are still floundering around using metaphors like 'wave' and 'particle,' neither of which has consistent descriptive power, we don't understand it in the way that we understand the macro world. Yet we are made of quantum stuff. Odd! Does it have to be so? Might it not be possible to have an intelligence which, by some means, is not separated from the quantum world by this intellectual barrier? Precisely. I often think that moving onto land may have been a great driver of technology and that, in the water, intelligence might prosper to great sophistication without it. The sea has little fluctuation in temperature, at least locally. It removes the need to invent flight. 😃 It allows long distance communication (eg whales.) It allows for long distance travel. A lot of inventing has already gone out of the window! Olly

What happens if you stack just the subs from just one side of the meridian? What are the stars like? I would try this for both sides, ending up with two stacks, but maybe you've done this. On the physical side, the obvious source of variance between meridian sides would be sag in the focuser, which would invert relative to the sky. It there is a slight distortion which varies each side of the flip, then the software's calculation of the stellar centroids may be thrown out of kilter, prducing bad registration. If all the subs on one side stack nicely, and all the subs on the other side stack nicely (using a sigma routine) then I wouldn't hesitate to align them in Registar and average combine the two stacks. Olly

Depends on the length of your OTA. If you want to observe at the zenith, the EP needs to be at an accessible height above the ground and not ridiculously low. It the instrument is rear-end heavy it will sit further forward in the saddle plate and not be as low. If the EP becomes too high it's less of an issue because you can rotate the diagonal to have it coming out horizontally. Olly

I share your uncertainties. How would I recognize it? I might not, which has been behind my repeated urging of caution against anthropomorphic assumptions about intelligence. However, I use 'intelligent' to describe entities, real or hypothetical, who can react to sensory information with the capacity to distinguish themselves from that information. That reaction must include the ability to manipulate the information and to speculate about it. In short, an intelligent entity must be self aware. Now some will argue that the self is illusory but I've never been able to embrace this view. If I stick with this definition I can conceive of entities who might accumulate quite different sensory information to that which I collect and who might manipulate it in quite different ways, using quite different media. (By media I mean what we call language. It's beyond me to conceive of the manipulation of information without some kind of medium in which to do it. We do it using words or mathematics, though perhaps we also think 'pictorially' in some ways. Sometimes the medium of our speculation can be impossible to pin down and may be unknown to us. I'm thinking of that moment when, after struggling with some puzzle, you suddenly think 'Got it!' without knowing how you got it.) So I don't think the term is empty so much as open-ended. Olly

But this is a conversation about potentially unknown life, so a scale which tops out at what we know, or can do, is hardly adequate. I'm not judging our intelligence at all, in this context, since I have no idea what other intelligences might be like. That's why I don't say that I think we're good at understanding things. We are better, it seems, than bivalves but we have no idea what an upper limit might be. As always, though, I signal clearly that I see no reason to suppose that advanced intelligence will necessarily lead to advanced technology. Olly

But we would think that because we are judging our own level of understanding with... ahem... our own level of understanding. Olly

Lord Kelvin, I think you meant? Unless Bernard Levin had a promotion that passed me by! 🤣 It certainly makes a splendid cautionary tale, whoever said it. Will anyone ever make the same mistake again? Given that Heisenberg thought turbulence too difficult for god, maybe not. Olly

To be fair, it may only have been one of them! lly

The whole point of the scientific method (and many branches of philosophy) is to get some control over assumptions and be aware of when we are making them. The history of science is, in many ways, the history of the deconstruction of assumptions. If you give in to assumption you leave the world of science. However, if you imagine that entirely excluding assumption will ever be possible your science will probably be flawed. Since assumptions of some kind are inevitable, the best we can do is be aware of them and declare them as premises of our argument. Do you want to declare that, for you, intelligence means human-like intelligence intimately interwoven with technology? I think it would be fine to state this but not fine to assume it. Olly

You're dong it again! 'Our level of technology.' Who is defining this scale of levels? You are!!! And how are you defining it? By going back over the evoloution of our technology. To reflect upon aliens we must stop reflecting upon ourselves. Olly

Why is radio primitive? Because it came before television? Radio is not primitive, it is fundamental. There's a difference. Olly

Do you regard assumption as a a valid component of critical thinking? Note your own (perfectly correct) statement, History is full of people who knew that they knew. Wouldn't it be fair to say that 'knowing that you know' is a very good way to define assumption? Olly

Have you reflected upon how many anthropomorphic assumptions underlie these arguments? The chimpanzee question Would be a pointless comparison. Only if you consider humans to be more intelligent than chimpanzees. If you do consider this to be so, why do you do so? Beware, this may be a harder question than you suppose. Can you answer it without using an anthropomorphic definition of intelligence? if Aliens were more technologically advanced. This carries assumptions that technology is an expression of intelligence. It is an expression of our kind of intelligence, perhaps, but it might also be considered an expression of our kind of stupidity, since we use our technology to destroy our own environment. Either way, can you provide a non-anthropomorphic argument to suggest that intelligence leads to technology? Also, if some species were more technologically advanced, we have no idea if we are interesting enough to them to want to bother to communicate. Can you define 'interesting' without any reference at all to the human notion of 'interesting?' It is an adjective which defines a human response to something. There might be other responses to stimuli which do not involve the human emotion of being 'interested.' History is filled with people who knew they knew. It is indeed, but when we talk about alien intelligence, may we not be guilty of knowing that we know what intelligence is when, in reality, our only knowledge of intelligence is based on our intelligence? So do we not impose upon alien intelligence the need for that intelligence to resemble our own? Olly

When did you last hear from a chimpanzee? They have a 99% DNA agreement with us and live on the same planet. OK, this question is posed light-heartedly but, if we think about it seriously, it tells us an awful lot about why we might not have heard from aliens, even those within communicating distance. Olly Edit: my question can be pushed even harder now that I think about it. When did you last hear from a person from one of the hundred or so remaining uncontacted tribes? You didn't of course, and neither did I, or they wouldn't be uncontacted. But you see my point, I'm sure.

Stunning result. Both star removal tools work best on narrowband, which is not surprising, really, since NB stars are smaller with tighter edges and can, therefore, be spotted more easily by the software. Olly

But... since computer games are made by humans, for humans, are they not bound to recreate worlds which humans can understand? In which case our world is bound to resemble the computer game world. We wouldn't be able to play a computer game located in a world of physics entirely different from our own. It takes only a small step to move from the view that there is our world and the game world to our world is a game world. Small as it may be, I consider this a step too far. Olly

Instinct told me to do it early but experience hasn't borne this out. I've had excellent results by going over old 'finished' images and de-starring them. I find I can them stretch them still further, with advantage - and especially if I give them a dose of NoiseXterminator as well. I then recombine them following Ciaran's advice on here. (Photoshop, paste starless over starry, invert both, top layer active, change blend mode to divide, stamp down (CtrL/Shift/E), invert top layer, flatten and save as stars. Paste this on top of starless, blend mode screen, then simply de-stretch to taste using the mid point slider in Levels. If working on new data I compromise, de-starring after a partial stretch. I find StarX works 9 times out of 10 but sometimes throws up a fatally checkerboard background too visible to fix cosmetically. Olly

Star removal and replacement might take this to another level... It's well flattened and colour calibrated. Olly

Just waiting for anyone with experience of building a 700 panel deep sky mosaic to chip in. My own experience of 35 panels would be totally irrelevant! lly

Agreed, though the banding is purely horizontal and it seems as if the rig was providing natural dither, so I think it may be inherent to the camera. I think PI has a tool to remove Canon banding and there is also a tool in the Ps actions set Astronomy Tools from Pro-digital. Has this camera taken proven images before in your hands? Olly Ed's post crossed with mine and looks promising.

I was also going to suggest the rolling sentry box ^^ as an option. It doesn't need to be any higher than the top of the scope but mine was built to cover a large instrument. I made mine by welding up a steel chassis but the easy way is to source a sentry-box like shed from a garden store and mount it on a rolling wooden board. This board just needs a slot cut in it to let it roll half way round the pier. You can also have some extensions protruding from the pier just above the height of the 'floor board' to stop the shed from lifting. I went for rails rather than free-running wheels. Whatever you do, be sure you have bomb-proof anti-lift built in. If it can fly, it will fly. Olly

I have a very nice Altair Astro scope handle. Right now it is deployed on our observatory door but it has also carried telescopes. They are also potential DIY projects, this one being quickly attachable to an SCT too heavy to be moved by one person (with the possible exception of the renowned imager Strong Man Mike who has been photographed carrying an observatory...) Personally, I think handles are sensible and reassuring things. Olly

As vlaiv has ably demonstrated, the answer is 'no.' However, I'll offer an equivalent but alternative explanation, more verbal than mathematical. You are, essentially, asking, 'Doesn't F ratio over-ride aperture?' If you asked this of a daytime photographer they would probably say, 'How can it? F ratio is aperture.' In the shorthand of daytime photography, that's how F ratio or F stop is used. This isn't formally correct but it works because, in their context, the focal length is fixed. If they switch a lens from F5 to F10 they open the iris and increase the aperture. In their case, the only variable is aperture since focal length is fixed, so lowering the F ratio physically increases the aperture. That's why they use F ratio and aperture interchangeably. In astrophotography we have two variables, aperture and focal length, so F ratio is not pinned to just one of these values as it is with a camera lens. We, therefore, have to wary of the term F ratio since, out of context, it has little value. Olly