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digital_davem

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Everything posted by digital_davem

  1. Physics is often very subtle and takes considerable skill to think about correctly. The lay person, without the requisite training, having an amateur stab at it, can sometimes get in an awful muddle and come up with seemingly incomprehensible paradoxes that are actually perfectly satisfactorily understood by experts. This is the normal state of affairs and popular science writers are accustomed to dealing with muddled enquiries from enthusiastic, but untrained readers ( one, I remember saying he keeps a list of the top 100 most common blunders made by amateurs who believe they have dispproved Einstein and simply responds to the regular letters he receives my returning the list with the appropriate numbered error ticked). The infamous scientific "crank" is someone with an obsessive and deep seated belief in some pseudo-science idea they have dreamed up that makes no sense to an expert. Professional scientists,if they were inclined to sacrifice the time to do so, could falsify these ideas without difficulty but they often have a very attractive allure to some lay people, particularly those with some kind of need to be different. The Internet is obviously a fruitful channel for expressing these ideas for people who in the past would have no recourse other than vanity publishing. Speaking of which, I have a wonderful self published tome in my possession by someone called Michael Pinder who declares himself the President of the Decimal Time Society. It starts off quite creditably and is well argued but before long, a simple idea (that we should decimialise time units rather than sticking with the familar base 60 seconds and minutes) morphs into a philosophical treatise into how the switch to decimal units would solve not only economic problems, but all the social ills you could imagine. And by the end of the book, even the text is no longer your familar fixed with set of letters but devolves into blocks of letters of all sorts of strange shapes and structures and the prose converts into rambling poetry. I'm sure there must be some intention behind this design but for something presumably intended to be persuasive to the makes of public policy, it resembles quite strongly the work of (at best) an amusing eccesntric or (at worst) a lunatic. Physics attracts many people and ideas of similar standing - presumably people drawn by the consideration of the infinite. Or something like that. Real physics is hard enough without the distraction of well meaning but silly psuedo-science.
  2. Planets get their rotation from their original formation and will retain it forever unless something interferes. In the case of moons that show the same face to their planets (tidally locked) they still rotate but their rate of rotation ("Day") has been slowed by tidal effects so that it matches the rate of their orbit ("Year") so they show the same face. They are still rotating though. I have no idea why you think their rotation has anything to do with holding them together. If anything, rotation would threaten to disrupt if fast enough (Saturn for example is significantly flattened at the poles because of its fast rotation). ps @Bomberbaz The Moon rotates just fine (if slowly) as does Mercury: Rotation period: Moon: 27.3 days Mercury: 88 days The slowest rotational period in our solar system is Venus: 243 days (which is longer than its year)
  3. The important thing is that we work on understanding the formation of the solar system. Pluto and the other KBOs have an important role to play way beyond what they are called. The weirdest factoid of all for me is that the current favoured planetary formation model (the acretion model) appears to be impossible as, while it is certainly possible to explain how dust particles combine to form pebbles, there is no known mechanism by which metre sized rocks colliding at 40,000 mph can acrete into a planetesimal...
  4. There are some useful group distinctions to make, I think. For example, Mercury, Venus, Earth, Mars are all small rocky bodies, Jupiter, Saturn are basically clouds of hydrogen and helium, uranus and neptune largely gas but with a higher proportion of ices. Of the moons, only Luna and Io are rocky, the others are very much less dense and icy. KBOs also tend to be icy and small. These bulk compositional differences and smilarities likely tells us much about the origin of these worlds -eg icy moons and KBOs are unlikely to have formed close in to sun as the volatiles would have burned off. Pluto appears to be a KBO type world with much in common with other KBOs. If this turns out to be the case and the mechanism of formation of KBOs is eventually worked out and is confirmed to be different from gas giants and terrestrial worlds, we would only confuse matters to insist on calling it a planet for nothing other than historical reasons. The IAU has tried to draw up a set of rules that may or may not make sense but there is more than arbritrariness behind it. The furore over Pluto's demotion is largely nothing to do with science anyway. A few vested interests (New Horizons, anyone...) and lots of people who learned the names of nine planets at school and are clinging to them out of nostalgia. KBOs (including Pluto) are fascinating and as a class of bodies deserve to regarded as every bit as important as the planets and these primordial bodies have lots to tell us.
  5. As fascinating as Pluto undoubtedly is, I suggest reading what Mike Brown has to say on the subject, rather than just the IAU. Essentially, Pluto is (the largest known) member of a fascinating family of objects that share similar characteristics and which are distinct from both the gas/ice giant worlds and the inner terrestrial planets in their properties (and likely, formation). These Kuiper belt objects are worthy of study in their own right and Pluto is right up there as a stereotypical member (as is Charon). There are already a bunch of discovered similar worlds starting with Eris that are equally entitled to be called planets if Pluto is to be regarded as a planet. Potentially there are hundreds waiting to be found. It is historical accident that Pluto was the first discovered and its only claim to be a planet. Pluto and the other KBOs have a story to tell that will reveal more about the structure and origin of our solar system. Let's not obsfuscate that important journey with childish emotional stamp collecting squabbles over Pluto's status and get on with finding out what KBOs have to tell us about how we got here...
  6. Fascinating to see these pics and sketches. What I see is a bit like the OP shot: but the four little stars in the middle are much smaller and closer together - really close together with hardly any space between them but they don't look like round blobs like above, instead tiny pinprick points, small and sharp. I don't see any of that cloudy stuff extending beyond the stars. Basically, I see a collection of stars, one of which is that group of 4 stars very close together and a small faint fuzziness around the collection. No structure or shape or clouds. Didn't even imagine that was visible at the eyepiece. Olly's picture is amazing. I looked at Jupiter again last night, a bit rubbish, if I'm honest, just a yellow disc with no detail. I think there was some kind of haze in the way because the moon was wearing a great big fuzzy halo. Clearly there is much more to see under darker skies. I was beginning to wonder what all the fuss was about with stargazing, just a few points of light, nothing to really see, a bit boring after a while. Obviously, I need to get up to our summer house near Galloway, London is not a great observing site... 3" classic refractor (f16.4). p.s. there is still something about seeing the Galeilean moons strung out in a line...
  7. Roy I see your sig now shows the re-worked scope. Time to give it a name, like Neil English does with his!
  8. Poor old Moon really took a pounding. The early days of our solar system were not a nice place to be... (interestingly, in my 1974 edition of the Observers book of Astromomy, SPM speculates on the origin of the cratering. The betting at that time was that it was primarily volcanic. Did we not know about the bombardment events of the eartly solar systems in those days? Presumably not. Evidence that science does move forward quickly, even if it isn't always obvious. There are a few more anachronistic sentences in that book. Who was it who used to say "We just don't know..." - was it James Burke?).
  9. Earlier. I was tracking the view using ocular plugin and I waited up until it was clearly visible in the sim at the limb (maybe about 1.30am ish) but couldn't see it at the eyepiece. It sits over the house in my north facing garden, probably doesn't help. Couldn't stay up any longer... Saw Io peak out from behind though
  10. Just saw a Porta on offer on Ebay for half the price of a Skytee and including legs in "as new" condition. Couldn't resist. The mount works brilliantly. It's much bigger in the flesh that it looks in pictures. The legs are large surveyor style but designed primarily for low weight and portability and are made from extremely thin aluminium box section that isn't particularly strong. The result is it bounces around a bit more than my manfrotto/pier arrangement. But there are clearly things that can be done. For example, not extending the middle bit and keeping it low and moving my home made pier over from the manfrotto to provide the height, sand as you suggest, and perhaps as each leg is made of three parts, extra clamping. People also remove the legs and replace them with wooden ones. Or get a different 2" leg tripod at some point. Couldn't fault the head itself though, it works great, transforms the viewing experience because it points where I want it to go and no clamps needed. Amazingly even though the saddle is vixen dovetail and my tube rings are bolted to an arca-swiss plate, the arca-swiss attaches just fine, despite being the wrong size and shape! I no longer need the heath robinson arca clamp connected to manfrotto plate arrangement either which removes two potential weak points.
  11. Got my first extended look at Jupiter from the back garden. Saw Io pop out from behind Jupiter. Cool! Couldn't make out the spot, though. Don't know if it was just inexperience. I have a new (used) mount: Vixen Porta II. It's amazing compared to my 3 way camera head: friction locked (no clamps), so you just push it. Very smooth! And love the slow motion. Not so impressed with the supplied tripod. It looks big and impressive but it is so light weight it is wobblier than my Manfrotto legs. Going to have to improve it or maybe swap head over to the manfrotto. Perhaps still have a set of EQ6 legs in my future.
  12. Hi I have just received a Porta II mount to replace my camera tripod. My telescope is currently mounted using an arca-swiss camera mounting bar/clamp which I need to replace with a Vixen/Synta style dovetail. There are many, many variations available online at all sorts of (often ridiculously expensive) prices. There are some cheap one too like the skywatcher ones. I've not seen one of these before so I'm wondering how they attach to the tube rings. I'm using Canon lens tripod rings with mounting feet like this rather than traditional tube rings, so the dovetail will have to bolt to each foot using 1/4" whitworth standard camera tripod bolts. Obviously the dovetail will need holes in and I'll need suitable bolts. Where to start...
  13. I don't think an individual's personal and private views really matter if they stay behind closed doors. The issue of bigotry comes to a head when a person acts on those views. If SPM actively disriminated against people who were members of groups he didn't like (or encouraged others to discriminate), that is what matters and when it becomes actual bigotry. I presume it is a matter of record what he said and did in his political activities so the facts will speak for themselves. There are plenty of stories that suggest there is something in the charge. Establishing the actual facts from the myths (and slanders) is always the problem, of course.
  14. I read an obituary of Patrick Moore in the New Statesman that was not so complimentary. Whilst acknowledging his greatness as a broadcaster and as an evangelist for astronomy and his personal kindness, it seems SPM had a bit of unsuspected darkside. Often excused owing to his age, old fashionedness and quirkiness it seems there was more than a hint of the bigot in his makeup. It makes rather less comfortable reading that most "SPM, the legend" pieces. It would be interesting if more about this un-publicised side of his character comes out in future biographies. If true, it won't diminish what he achieved in my view, but it may take a little of the shine off my liefe-long hero-worship. http://www.newstatesman.com/martin-robbins/2012/12/sir-patrick-moore-great-and-bad-man
  15. The owner of Skylight telescopes invited me to buy one a few days ago. Might be worth contacting him.
  16. Caltech news has a good readable write up from Mike Brown and co. In that they say they assume it would be a mini-Neptune and the back of envelope estimates are based on that.
  17. Well, possibly - but not yet demonstrated convincingly. One of the interesting things about the current leading theory of planetary formation (the acretion theory) is that no one has yet made it work. How do metre size boulders that hit each other at huge velocities stick together to build planetismals? No one knows, all the models display destructive behaviour at those object sizes, not acretion. It's an ongoing mystery (and area of research). There's an accessible and interesting introduction to the question in this book: http://www.amazon.co.uk/Exoplanets-Alien-Solar-Systems-Yaqoob/dp/0974168920/ref=sr_1_1?s=books&ie=UTF8&qid=1453130217&sr=1-1&keywords=exoplanets+and+alien+solar+systems
  18. That That's interesting - do you have links or any more info?
  19. Done! I taped a small artist's paintbrush to a chain of wooden cooking skewers. Very bendy! I mixed the blackboard paint with flour to give it more texture then painted it on all the baffles and the tube walls in between. Not so easy to paint with a bendy 3 foot long paintbrush but I got there is the end. I also painted the focuser (baffles, inside tube and any external surfaces and edges that looked like they could reflect any light anywhere. Looking down the tube from either end reveals it is now very dark in there. No idea whether it will make the slightest difference, opinion's around the web differ widely, but can't do any harm.
  20. Hi Folks Given the wonderful equipment and software that is available to us today (compared to, say, 30 years ago), amateur astronomy is more sophisticated and in some ways much easier than it used to be. It is also much cheaper (although there is still a lot very high priced gear) thanks to Chinese industry and opened up to massively more people than it used to be. Obviously, when the telescope was invented it opened up whole new areas of investigation and thought to the likes of Galileo and chums. As telescopes and observing improved through the enlightenment period and into the 20th century, theory and observation worked hand in hand to develop current day astronomical and cosmological understanding of the origin and lifecycles of planets, stars, galaxies, the multitude of other astronomical objects, the nature of space, time, matter and energy and ultimately the origin and fate of the cosmos itself. Heady stuff and still a way to go yet in completing the understanding and coming up with that elusive theory of everything. But this is all the realm of professional astronomers and physicists; not the remit of the amateur stargazer. Looking at my old introductory astronomy books from the 1970s, it seems to be all about gaining a sense of wonder and introducing the ideas of science. But today the internet gives us easy access to the amazing photos from large telescopes, space telescopes and robotic probes vastly superior to anything you'll see through the eyepiece and a huge range of educational resources free of charge. Basically, you can educate yourself to quite an advanced level, you can explore the surface of mars, see close ups of the moons of Saturn even details of the geology of pluto without ever donning hat, scarves and gloves and venturing out to the back garden at midnight. So, what is the point of amateur stargazing in the 21st century? It's not going to advance our knowledge, it's not going to educate you on its own. Is it equipment lust, space tourism, gawping at the sky, is it an escape from the pressures of everyday life, or something else entirely? Share some insight about what motivates you and why star gazing is important today....
  21. The trouble with my telescope is you'd need a 3 foot long spray nozzle to reach the middle! I'm going to mix my blackboard paint 50:50 with flour (plain, I think) to create a flock-like 3d paint (some suggest crushed walnut shells) and apply it a dab at a time with a small brush attached to a thin stick. I imagine it will take a while! The big baffle near the objective and the smaller one at the eyepiece end and the interior of the focus tube should be reason straightforward but it's a long way to the centre sections with access through the baffle holes making it trickier. The two centre sections of the tube walls are a beautiful polished metal as well. In theory, the baffles should make this not matter but from my experience of using old unblackened camera lenses I'm suspicious of unpainted metal.
  22. Flocked the inside of the dew shield. Blackboard paint to be delivered tomorrow. Hope I don't make a mess of the internal painting - big gloopy blobs on the knife edges of the baffles probably a bad idea...
  23. UPDATE: I have flocked! I did the front section behind the objective to the first baffle and the section in front of the focuser up to the last baffle. It looks to me like this latter section was originally given some matte black paint in the factory but more a light dusting than a full coating. I have also flocked either end of the focuser draw tube up to the baffles inside the tube. That leaves the baffles and the two middle sections of the OTA between the centre baffles which seem to have been left with a remarkably polished chrome finish out of the factory (!), and the interior and baffles of the draw tube. I'm considering getting some blackboard paint for these. I read somewhere that it works better if mixed 50:50 with, er, flour. Plain or self raising, I wonder? It looks pretty tricky to get access but I'm thinking of something like a paintbrush taped to a cane or something. The flocking material (from Wilkinsons/Wilko) also serves double duty as new felt for the dew shield. Better that the electrical tape I've been using which made the dew shield very difficult to remove. I've also lined the edges of the Finnish Licorice tin lid I use as a lens cap. It's now easier to get on and off. No idea if any of this will make the slightest difference but it feels like I've done my duty Dave
  24. A clear night to my amazement. Don't like scaring the neigbours by sitting on my doorstep with a telescope, so need targets to be in the gap between my house and next door so I can set up discreetly in the side passage. And jupiter was just sitting above the rooftops at 1am for my first look. Four clear moons in a line, one a little below the others. Jupiter a yellow disc with hints of stripeyness that kept fading in and out of focus. Quite surprised at how small the field of view is and how quickly the planet runs away. Can also see the limitations of using a camera tripod and mount with a classic refractor. Even though the mods I made have made it taller and more stable and it only takes a few seconds to stabilise, the biggest irritation is aiming the thing. When I loosen the clamps, centre jupiter in the circle, tighten the clamps again, there is enough slop for the scope to move slightly - just enough to either go out of the frame or end up on the edge where it disappears very quickly. I have no idea whether something like a skytee or an AZ4 is precise enough to avoid this slight shift - it's very frustrating. Anyway, nice to see the king of the solar system for the first time. Wish it was 4x bigger and twice as contrasty though ;-) Prinz 660 3" inch classic 1250mm f16.4 with Antares 12.5mm plossl and Celestron x-cel LX 7mm ( 100x and 175x ).
  25. How about Pleiades? Plee-i-dees, pliar-dees, play-a-dees?
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