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The Admiral

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  1. Andromeda DSLR and focal reducer

    Don't expect it to be the "Bee's Knees", but at least you'll be able get an idea what 30s subs can do, with a 102mm at about f/5.6. Ian
  2. M42 au chocolat...

    That really is a startlingly deep image Olly. The sky abounds in detailed structures we rarely ever see. Thanks for that. Ian
  3. Andromeda DSLR and focal reducer

    It's in my album or click on the link in my post. I'm sure the info in my album is wrong, it certainly will be a lot more that just 10 subs! Well, before looking at the many factors which could improve your image, I'd suggest maximising the quality using existing data first. You could try uploading the stacked image to a file postbox and let others have a go with your data. What processing software do you use on your stacked data? You should use your RAW files in DSS if you are not already. Ian
  4. Andromeda DSLR and focal reducer

    Hi Craig, you should be able to get reasonable results with your 2min sub length. For us users of Alt-Az mounts we are constrained to rather shorter exposures. I use 30s on mine. I think I used roughly 150 subs on my M31. As others have said, it's the processing that can make or break an image. Ian
  5. shed size 6x6 or 7x5

    Diddy men! Sorry, I'll get me coat! Ian
  6. Googling Promethium, it seems that it and only one other element, Technetium, have isotopes which are all radioactive. In other words, they essentially are not found in nature; if they ever were created cosmically, they are long gone. They will require artificial production. Ian
  7. Sorry, how can replacing the focuser, which is a non-optical device, change the focal length of the 'scope? Surely, that will be determined by the mirrors, unless you are using a reducer. Do you mean the amount of back-focus available? Sorry, I only use a refractor, perhaps I'm missing something. Ian
  8. That's a nice strong, colourful image Neil, with the whole of the 'smokey ring' visible. If you take some more subs on this, perhaps some rather shorter ones so that you can get some definition in the core? Ian
  9. The "No EQ" DSO Challenge!

    Ah, in your signature, just realised that Ian
  10. The "No EQ" DSO Challenge!

    That's nice Shaun. I like the star colours and sharp stars. What equipment did you use for this please? Ian
  11. Indeed fission is the breaking apart of the fissile nucleus, but what happens is that in the high neutron flux some fissile nuclei can acquire neutrons and through a series of interactions and decays, the actinides can be built up. For example, Plutonium-239 is created when U-238 acquires a neutron to become U-239, which then decays to Np-239, which then decays to Pu-239. I think that the presence of elements with a mass greater than iron is a reflection of the material which formed the star, created from other stellar evolution processes. My point about there being fissile material on earth is that it is present in sufficient quantities, and will also be present in other stellar bodies too. The concentration of fissile elements in Przbylski's Star will have come about by the magnetic separation that apparently happens in this type of star, and crucial to my postulation is that this is the very process by which sufficient fissile material could be confined to give rise to a chain reaction. It always amazes me how so much information about other bodies can be garnered so remotely! Ian
  12. Sorry, this should have gone in the physics and space science category. Would a mod move it please? In a recent thread a question was posed about about the origins of the relatively short-lived transuranic elements found in Przbylski's (apparently pronounced 'sha-bil-ski') Star. Being short lived, they must be being continuously generated within the star. But how? In the article in 'Astronomy Now', the production of such elements was considered by Vladimir Dzuba as possibly being due to the decay of super-massive elements with masses way beyond what we can currently manufacture on earth. On earth, of course, these transuranic elements are produced as a by-product of a process of nuclear fission in a nuclear reactor. The fission process gives rise to a large neutron density within which the transuranic elements can build from the uranium fuel. Such a process can also occur naturally; there is evidence that some 2bn years ago, within the uranium-rich deposits in the Gabon, the same process took place for a million years or so! This fission chain reaction can also take place in a rather uncontrolled way, such as in nuclear weapons. Such 'critical events' occur over very short timescales and there is the potential for large amount of energy to be released over short periods of time. Musing on this, at this point I started to take leave of my senses and to speculate somewhat wildly . Apparently, one of the features of this star is that the star's associated magnetic field traps the various elemental species in layers in the star's atmosphere. I began to wonder whether it would be possible for a shell of fissile material to build, and for this to undergo a fission chain reaction. This could be a fairly sedate and continuous process, a bit like the nuclear reactor situation, building up the transuranics that we believe we can detect. On the other hand, I wonder if the fissile material could build to the point where a spontaneous chain reaction can take place, spreading throughout the shell and around the star in a flash. A nuclear explosion, if you will, engulfing the whole of the star's surface! That would yield a vast amount of energy over a short time, and, in turn, could also build the transuranics. Perhaps the cycle repeats itself every so often, to keep the short-lived transuranics in place. So the star is undergoing both fusion in its core, and fission in its outer layers. And then another wild thought crossed my mind. One of the features of such brief 'criticality' events is the production of a spike of gamma radiation. So, extrapolating to the stellar situation, I began to muse on whether the rapid chain reaction could be the origin of gamma-ray bursts! It would be interesting to know if spectra have been acquired from such bursts, and how they might compare with what would be got from a nuclear criticality event. Well, there's no harm in letting the imagination run wild! It also helps not being too well versed in stellar evolutionary processes . Mind you, Przbylski's Star is a bit of an enigma, so perhaps that's not important anyway. Ian
  13. FLO Banner

    It's not showing on my Android tablet in the default simple theme, but does in the other ones. I'm not aware I'm running any ad blocker. Ian
  14. I read that article too. A very interesting star, without doubt. My understanding is that they believe they have detected these transuranics, the actinides. They are radioactive and have relatively short half-lives, but even then we can be talking about tens of thousands of years. Still, this is miniscule compared with the life of the star, so there must be something continuously generating them. Now this can be done by building them up in a highly neutron rich environment, as we do on earth in nuclear reactors, or through the radioactive decay of even more massive nuclei. The problem is, as the more massive a nucleus becomes, so the shorter its half-life becomes. In other words, such more massive nuclei would disappear even faster than the transuranics. If you search for 'islands of stability', you'll find articles which discuss the prospect that some way beyond the nuclei we can currently create, there may exist even more massive nuclei which are much more stable, and whose half-lives become significantly longer. I don't think we are talking of totally stable nuclei here, but perhaps nuclei with, I don't know, half-lives of millions of years, or at least comparable with the age of the star. From what we are told of this star, it seems that the star's magnetic field is separating these elements in the star's atmosphere. So I wonder, given that these transuranics, and indeed Uranium itself, can be fissile, that in some of these 'shells' of elements fission reactions may be taking place, and creating the actinides in the same way as we do on earth. In which case we'd have a star undergoing both nuclear fusion and fission! Not in the realms of fantasy I would have thought Ian
  15. Overseas supplier dispute advice?

    Oh, that's a bit disappointing. I guess one needs to be a bit pragmatic now and move on, and accept that as long as it works OK, then try to forget the rattle. Altogether a totally unacceptable experience. It's no way to run a genuine business these days, apart from which it's too easy for them to lose credibility in our interconnected world. Fingers crossed! Ian