Green Baron

Paper by the thirsty guys: https://arxiv.org/abs/1703.10803 :-) Apparently submitted one day early ... Edit: oh, and i am late by more than a month , sorry @Spaceception, i didn't scroll high enough.

Usually i am the one pulling the brakes, but i actually find this a good idea to study the effects of interplanetary space on the human body in a long term stay. And a logical step. Though ten years from now seem sporty to build a habitat around the moon ? Concerning SpaceX i have my doubts that things will work out as envisioned. Next step fh, then the tourist mission, ... we'll see :-)

Nope. My intention was rather to point out that it is incredibly inefficient (and impossible with current technology) to mine anything in industrial quantities anywhere else than on earth. To get just a spoonful of anything from even the moon to earth is totally beyond any economic reasoning. Just take a look at the energy balance for getting there and back again (a CH2 molecule's tale). Even if hydrocarbons (for whatever application you might imagine) would run out it would make much more sense to find workarounds, other technologies like electricity for transportation, production of surrogates through bacteria (SciFi, i know :-)) or something that has yet to be invented. Right now "we" aren't even able to establish a colony on the moon, or in the deserts on earth or at the south pole. The few scientists/military men and women there had no chance if they weren't supplied from outside. Becoming sick at the south pole in winter is life threatening. Fully robotic and self sustaining plants don't even exist on earth because maintenance, replacement, use wear. The idea of mining other bodies is a play of the mind, a computer game. The enthusiasm might be awesome, but it's unrealistic. :-)

And that is why i hope that OP will join others who fly similar things, who have a a small airfield, know the regulations, can help with constructive things, and surely can help him with his "stove pipe" :-)) And i admire people who build and fly things in real world :-)

Piston engines don't, jet engines are likely to do. It's advisable to fly them on e registered model airfield and since many them are above 20kg they need some registration and maybe even a clearance anyway.

If you are below 20kg max tow and your rc controller stays within the limits of frequencies (list is publicly available) and transmission power (depending on frequency between 10 and 100mW me thinks) then you are legal. If you stick your nose over 500 feet above the ground you are about to make step towards jail if endangering other traffic. Interfering with air traffic or abusing frequencies are no legal peanuts as you might not know whom you disturb in the vicinity. So, if you didn't know before, now you do. Nothing personal :-), I only post this to avoid further legal limitations to all the serious rc model makers, which is the case after the incidents we had and still have. Edti: as you ask the internet, may i suggest to ask people from an rc model makers clubs who have an own little airfield and fly models with jet engines ? They might have solutions for your questions, including the technical ones, though most model engines are real turbines.

Maybe you find something to watch when searching for giant impact hypothesis. I have seen different ones simulations, the latest from just a few years ago when the impact angle was recalculated but i couldn't find it now. I think it was Science magazine ... The stable orbit thing comes quite automatically. The two cores of the bodies (they just had differentiated) united. Part of the mantle material was ejected into orbit and most of it just fell back. The rest gathered around the wobbling new mess err mass and did what it could do best: formed a disc on a low orbit with a few bigger lumps that served as condensation cores. It started on a quite low orbit, tidal forces let it slowly drift higher. Edit: Here you go, @vger not a cinema style motion picture but a nice visualisation.

Yes, i tried with paper (is has enough space :-))). Also i used a file to roughen the surface of the part that fits into (not the eyepieces of course). But since a am used to the 2,5 inch feather touch (FT) on the apo i don't tinker with that thing any more. The FT has three screws and they fix things without the slightest force, just thumb and index and a stretched away little finger. It is rather a problem to get things out when angled than to fix things.

Fully cardanic suspension is what your looking for i think. If you could visualize your idea ? 3 drives would have to rotate with the corresponding axises, i doubt that this can be realized irl. Real world gyros operate in 1 or 2 axis, so one needs several for 3 axis steering. Also they must be calibrated every now and then due to friction. Gimbal lock becomes a problem as soon as you have two degrees of freedom ...

It slides out when there is anything heavier than a small eyepiece, even when all screws are fastened. For example, i have 100° eyepieces but they are too heavy. So is the dslr camera. My other complaint is that it only has one screw to tighten the fitting. There is always a few degrees of play in the system. And it doesn't close very will, mirror and small eyepiece turn slowly but steadily towards the center of the earth. A reasonable focuser has 3 screws 120° apart like a star, so that nothing can wobble.

What's that fuzz about mining solar system bodies anyway ? What do they have that we don't have here ? There is no technology, no patience nor even the will to do so. We don't even know whether anything suitable is there in a form that can be "mined" at all. Hydrocarbons ? How many thousand thousand tons would you have to burn to get a single one back ? Yeah, they may run out, but we might use much less in the future when electric transportation slowly takes over (assuming political will here). It'll be easier to "mine" lumps of ore from the ocean floor. How much energy, effort and resources would it take to build, launch and maintain the necessary equipment ? Far out of range for any economy i can imagine. Its pure sci-fy, if at all.

This is one possibility when you have a huge mount compared to the weight you put on it. It looks like the guy uses less than half of the mounts capacity. I have the same refractor, but i can only use it as a guide scope because of the crappy focuser. Balance is the issue with this style of setup because it might be difficult to have a comparable weight on both rails. The vixen style foot of the ES ED80 is indeed a problem if you don't have a vixen style mount (proprietary stuff :-)). But you can screw it off and use two rings instead like i did, which gives even more flexibility. I can use the small refractor alone with a common 2" rail or mount it with two screws on top of the apo as a guide scope. I even dare to claim that that is the cheaper variant ... Saving the money for a real thing is always a good idea !

Totally OT, but when i googled Fry (whom i did not know before but who seems to be reasonable man to me now) i immediately thought. "Oh, Mycroft Holmes !" This is a funny effect of the media age. When i saw the Lord of the Rings first, the scene where Frodo wakes up in Rivendale my thought was "Welcome to Rivendale, Mr. Anderson !". Sorry, random thought :-)

Wow ! There is a 152/1200 on sale with a strehl of .99 ? I would give my 115/805 away, but my poor G11 would surely straddle. No way ... TS (http://www.teleskop-express.de/shop/index.php/language/en/) have a good reputation. I actually have the exact same small flattener/reducer 279. The Orion's sword i showed off was made with it and you can see no vignetting with the 4/3-sensor. If the small refractor has no faults and a reasonable focuser for photography then why not. I found this one on their site but attention, it has the super expensive feather touch focuser and is probably not directly comparable to the tube from the offer ! Good luck

Errr .... APM sell that set new for 600,- 665,-. The refractor is an achromat. Has it even a glass lens :-) ? Edit: i gave false information about the refractors vom LZOS. The sizes from 123mm on are still on sale. Example. So easy to spread fake news because of information from another forum. Sorry ....

Apos are a very heterogeneous family of instruments. I have a cheap (well, it once cost 800 funds) china made "apo" , also with an ED-element, an Explore Scientific 80/480. Optically it is nice, but the focuser is absolutely unsuitable for photographic use. But i heard then even the optical quality varies greatly. The objective can be adjusted with screws, but that'll be another 100,- if you take it to somebody who can do it right(tm). I have heard good things and terrible things about the Skywatchers Apos, both concerning optical and mechanical quality. Then there are all the house brands of amateur telescope shops, in Germany that is Telescope Service in Munic and APM in ... forgot. APM were the importers of the fantastic Russian LZOS objectives, the best you can buy if you are looking for an air spaced triplet. But in the meantime LZOS stopped supplying amateurs. If you can get a grip on a used 115/805 or even 130/780 (THAT is a dream machine for DSO photography !), but i doubt that anybody who is content sells such a thing. Haven't seen a single 130/780 on the second hand market in 3 years, though it was produced over decades. The other well reputed source for air spaced triplets would be the Japanese Takahashi with Minolta (i think) objectives, the 120 and 130 are still portable and probably don't bust your mount, if it carries the 11" bucket. Then there are the oil spaced triplets. There are disputes going over what is best. German Zeiss were the first ones in the last millennium to build these, but Zeiss doesn't supply amateurs any more. TEC, Astrophysics and the newly come up CFF are reported to make first class telescopes, but oil spaced do have their own problems. For me it is an absolute no-go to wait years for a TEC or Starfire. That keeps the prices high. They are very prone to wrong storage and temperature compensation, and after ten years they might need an "oil change". Price / risk ratio is too high imo. Maybe an air spaced objective lacks the last 0.05 strehl in comparison to an oil spaced under optimal conditions, but it keeps its performance over a very long time (decades) and under very wide conditions if handled with care. If money is the second criteria after reliability then try and get a TAO 120. Plus reducer. Plus flattener. Different versions. Nice 100° eyepieces ... *rolleyes* :-) Edit: oh, an 80mm, well, how about one of the small Takahshi FSes ? I fear that is the case for a real one. A nicely made 80mm fluorite APO (no ED !) goes over the counter for 2.500,- ...

That may now be a terribly stupid question, but isn't the Schmidt-plate meant to correct aberrations of the main mirror ? Edit: (i always edit) no, it is not. Not off axis aberrations. It was a stupid question. Because i am an ignorant apo user :-)

Hmm, that makes me rub my chin. I thought you owned one of the Schmidt Cassegrains ?

Well done Sir ! Is that a little coma i see on some stars ? May i ask what you focal ratio is ? My setup rests under a blanket. Sky is clear right now but i can read a book outside because of the bloody moon. It'll be dark in the morning hours but that is not my time. Since i have f/7 i will have 4min per frame for the object, even with the ccd. If i wanted 10 frames per channel that'll be 160 minutes, plus 10 * 30sec L for a little hdr against the probably overexposed centres + changing filters that's more than 3 hours. I hope i am planning that right, it worked with M42 in January (2min / exposure).

Hi, i think there are a few programmers here, so maybe this is not the completely wrong place to ask. For one who has too much time and learns c++, trying to bide time, maybe with a little graphics stuff, what would you recommend, OpenGL or Vulkan ? I take it these two have completely different approaches, OpenGL being the more versatile and powerful, Vulkan more basic and apparently an answer to mobile contraptions. I should decide because i don't want to do two different things (limited brain mass). OpenGL seems to have stopped evolving 2015, is that a bad sign ? Both seemingly have little object orientation. I will surely always stay on pc, mobiles scare me. If someone of you has chosen in the recent past, what was it what were the criteria ? cheers gb Edit (i always edit): i am fascinated by OpenGLs GLSL and the parallel computation power it could bring to a program ...

Not sure about the inversion thing of space and time in a black hole, time ceases to exist after being prolonged almost infinitely compared to the rest of the world. I am on the no space without time side, at least not under our set of rules. No time, no change. Has change always a coordinate ? A particle moving, a wave propagating ? *shrug* There is a limit of what we can describe with our cosmological models right now and the question of what was the universe like before the inflation thing aka "big bang" can not be answered yet. Moar theories :-) Highly theoretic constructs like M-theory or string theory seem to allow almost any answer to any question, including 42 to no question :-) We grant Einstein's Old One another few decades before we call him to account :-) Edit (i always edit): didn't i find it or has this Einstein citation not been translated into English ? In a letter to Nils Bohr 1928 he wrote: „Die Quantenmechanik ist sehr achtunggebietend. Aber eine innere Stimme sagt mir, daß das noch nicht der wahre Jakob ist. Die Theorie liefert viel, aber dem Geheimnis des Alten bringt sie uns kaum näher. Jedenfalls bin ich überzeugt, daß der nicht würfelt.“ "Quantum mechanics is very imposing. But an inner voice tells that me it is not the real McCoy yet. The theory delivers a lot, but it does not take us closer to the secrets of the Old One (der Alte). I, for one, am convinced that he does not roll dice." Personal remark: "he" with emphasis and without a name in German can be understood as a little downgrading.

Oh, i see :-) Of course, that doesn't work ... how silly from my side :-) Edit: no, you could use the north pole as well, but it takes a little longer and some preparation. Also you need two groups. Drop a buoy at the pole if no ice. One group flies directly to the pole (heading 0°) thus crosses it sooner than later. The other one flies a loxodrome, a steady course of lets say 300° aaaand guess where they end up later than sooner ? Now, both flew a steady but different bearing and arrived at the same spot. How comes ? Edit: correction: 270 has a special case where it doesn't work, the equator. So we take 300 for example to save fuel.

Luckily we have two of these poles. The north-pole is frequently crossed on intercontinental flights. Would that do as well ? I would accept it as a surrogate for the south pole, but you never know what excuses come to peoples minds ... :-) Edit: it might be connected to air traffic regulations: planes are only allowed so far away from the next airport.

Aircraft behaviour is perfectly covered by theory and practice. Did you know that even the most complex aircraft are completely constructed in computers and on paper. Then a prototype is built and it flies and behaves exactly as calculated ? Would be possible if anything of what you call theories had flaws or exceptions ? You can try that yourself with a model aircraft from balsa, it is actually not difficult. Boys (and girls, sorry dear ladies !) 40 years ago did so. And still a few today i hear :-) Changing subject ? Many here know how black holes are described in theory. And in practice maybe at the end of the year when luckily the first images of the shadow of an event horizon is published. If not, probably next year. There are no defects, only things waiting for discovery. I didn't post against you, sorry if you feel offended. I wanted to make clear that flat earth (which was set into the antique before my post) is rather a modern thing than an antique. It was decreed in the Renaissance with reference to the late roman mathematician C. Ptolemaios. The antique world certainly knew that the world was round, though the exact diameter could not be measured until ~250 before christ. It was estimated too small before. Since the Rennaissance it comes up every now and then and today it has a fan base as described by @vger for example, but these are modern cultural excrescences, not ancients. Sure ! By all means, go ahead ! Again, sorry if i have upset you, and i will do as asked :-) gb

Thought this was about aircraft behaviour, not flat earth bs. For the 10th time or so: Eratosthenes I don't like linking to wikipedia but for all the doubters it's the fastest way now.