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    • CommentAuthortensor
    • CommentTimeJun 19th 2010
     
    @sonoboy, Congratulations on first light!
    I was at my cabin last night, excellent dark-sky location, I could see (un-dark adapted eyes, brief glance) 5 or 6 stars in Coronae Borealis which this link http://www.aavso.org/vstar/vsots/0100.shtml tells me is 4-5 magnitude.
    Doggone it, you guys are gonna get me to reactivate another dormant hobby. Must...resist...Visa charges....
    Ah, the hell with it, it's just junk fiat gov't trash paper anyway, actually electronic analogs of junk fiat gov't trash paper, which I can convert to actual real physical stuff.
    Hmm, how much is that 11 inch Celestron, anyway :)
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      CommentAuthoralsetalokin
    • CommentTimeJun 19th 2010 edited
     
    Here's last night's image of the Dumbbell. It's very interesting -- I think -- to compare this one, taken with the filter, to the last one taken without the filter. The central white dwarf's little yellow companion isn't visible in the new exposure even though there's a lot more light captured...

    I have got to get my hands on a set of color filters. Ordinary RGB filters are not very costly, but the really interesting pictures are generally made with H-alpha and Oxygen III narrow-band filters and they are quite expensive. It may be some time before I can afford the narrowband set, but I should be able to put together some RGB pix before too much longer.


    And here, incredibly, is the jpeg of the .bmp of the original image stack , before processing by various means including deconvolution filtering (PLOL, are you paying attention?). I am totally amazed that the software can extract the information that is there in the original.
    • CommentAuthorsonoboy
    • CommentTimeJun 19th 2010
     
    The 11 inch celestron on the cg-5 (which is a discontinued mount) can be had for under $2300.00. I think I've seen it for as low as $2099.00
    • CommentAuthortensor
    • CommentTimeJun 19th 2010
     
    sonoboy:
    Thanks! Now I just gotta get to the gym, so I can bulk up to lift the dang thing!
  1.  
    Sigh. It looks like a clear, if windy, evening, but the weather forecast is for scattered thundershowers.

    The cost of the telescope itself is just the beginning, as I am finding out to my chagrin. And enjoyment, for sure !

    Aperture is great, but for me in my situation, I am daunted by the size of the 9 1/4 inch model, and eleven inches is...well...somewhat like hard core porn, if you know what I mean. Looks like a lot of fun but there's no way I could handle that thing. I do plan on getting on the wait list for a 9 1/4 inch Celestron EdgeHD OTA, once I recover from this latest debauch, and I've already got a CGEM mount coming...allegedly coming...from a dealer that advertised them "In Stock!!" Well, they are all the way across town, and it's only been three and a half weeks since I walked in and paid cash for it...Hmmm....I wonder who that fellow behind the counter was, anyway. Haven't seen him before or since...Oh well, never mind, maybe it will come on Monday.
  2.  
    Might as well post this here, since the cosmos is bound to be electric, after all...

    This is a scan of the result of an experiment in wire explosion. I sandwiched a curved length of hair-thin enamel-covered copper magnet wire between two sheets of fine-art watercolor paper, stacked between some dielectric plates, and weighted the whole sandwich down with some heavy lead blocks. Then I charged up some 30 kV Maxwell pulse caps up to way over 30 kV with a Bonetti machine, and used a passive overvolting spark gap to discharge the accumulated energy into the wire.
    I believe this is a key experimental result that largely refutes the "Ampere tension" hypotheses of Peter Graneau and Richard Hull. In all fairness to them and others, I have also been able, by carefully tuning parameters, to produce evenly-spaced wire segmentation, but examination shows these segments to be produced by pinch forces, not longitudinal stresses as Graneau believes.
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      CommentAuthorlegendre
    • CommentTimeJun 20th 2010
     
    Are the small reddish dots globules of wire enamel?
  3.  
    No. The bright dots are copper globules; the reddish-brown dots are scorch marks on the paper where the copper globules were. Many of the copper droplets have fallen off, sadly, even though I sprayed the thing with fixative.
    The most amazing thing happens to the wire enamel. Frequently, it survives, in long lengths, tiny perfect...empty...tubes of enamel. There aren't any showing on this image; they are incredibly fragile and it is a mystery to me how they can survive at all, since the copper within them is vaporized and evidently ejected at high pressure.
    In other places the enamel vaporizes completely and contributes to the wonderful colors in the remnant.
    • CommentAuthorsonoboy
    • CommentTimeJun 20th 2010
     
    Hoo Boy!! High energy capacitive discharges! (rubs hands together in glee!!)
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      CommentAuthorlegendre
    • CommentTimeJun 20th 2010 edited
     
    @Al

    Now that's interesting, though not entirely unexpected. If you've ever used a solder pot to tin enameled wire (which I would expect you have), you know what I'm on about.

    Pot temperature is fairly critical; if it's too low, (or even too high under certain conditions), it only hardens the enamel on the wire. The enamel converts to a state that is very resistant to even higher temperatures, and requires mechanical removal to re-attempt the tinning operation.

    While I'm not so surprised that the enamel survived the very high temperatures, I'd like to understand how the molten copper could transit the enamel envelope, while leaving the latter mostly intact.

    Have you observed similar effects, when the wire is exploded with low voltage, low impedance sources?
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      CommentAuthorAngus
    • CommentTimeJun 20th 2010
     
    Just an aside... in some of the early single mode fibres it was found that when you put a really large amount of optical power into the core, the field at the reflection from the far end could break down the glass. This could cause another reflection, and the entire reel of fibre would hollow itself out - 100 m of glass thread with a 2 micron hole exactly down the middle. Weird.
  4.  
    Posted By: AngusJust an aside... in some of the early single mode fibres it was found that when you put a really large amount of optical power into the core, the field at the reflection from the far end could break down the glass. This could cause another reflection, and the entire reel of fibre would hollow itself out - 100 m of glass thread with a 2 micron hole exactly down the middle. Weird.

    That is weird, and interesting, and also I just might have an immediate application for this serendipitous technique. I know someone who needs a bunch of microchannels with sharp edges; perhaps some bits of your hollowed fibre could be stacked together side by side in an adhesive matrix, trimmed and end-polished and flushed to yield the kind of structure required. Normal production techniques don't yield sufficient enough uniformity or edge-sharpness in the hole size required.
    100 nm diameter holes would be even more desirable...a special prize for 10 nm holes in a plate 1 mm thick...1 nm holes with nice sharp square edges in a 100 micron plate would get you the keys to the lab...
  5.  
    Posted By: legendre@Al

    Now that's interesting, though not entirely unexpected. If you've ever used a solder pot to tin enameled wire (which I would expect you have), you know what I'm on about.
    Of course, and there's a wide range of enamel compositions, some more heat-labile than others, and some magnet wire is double or triple coated.


    (snip)

    While I'm not so surprised that the enamel survived the very high temperatures, I'd like to understand how the molten copper could transit the enamel envelope, while leaving the latter mostly intact.
    Mee too. This work was done at Building 29 on the old Alameda NAS, in complete isolation, which was good because the event sounds like a gunshot when it fires, and I don't (yet) have access to a soundproof workspace to repeat the work. I've saved some of the enamel tubes from those days, though, but I don't have them here. Some bits, the outer enamel from #36 or #40 magnet wire, could be several cm long and seemingly intact, although I did not examine them microscopically. The parameters have to be tuned fairly well to produce these tubes, IIRC; a bit too much energy or too slow a rise and the whole thing just vaporizes, sometimes taking the platens with it. I did a 1 mm wide strip of aluminum foil about 10 cm long, with 0.3 uF charged to 60 kV and an inductance made from 10 feet of #00 braided cable wound into a 5 turn spiral...it blew holes in both upper and lower platens and destroyed the contact arms, lifted the lead blocks about a foot...

    Have you observed similar effects, when the wire is exploded with low voltage, low impedance sources?


    No. At first pass, I'd guess that it would be difficult to get enough energy in a low-voltage pulse to do these kinds of things. We are talking multi-kiloAmp peak currents at 60 kV initial voltage for these effects even in tiny wires.
    I'd like to get my hands on a big industrial homopolar generator and try it, though.
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      CommentAuthorAngus
    • CommentTimeJun 20th 2010 edited
     
    Posted By: alsetalokin
    Posted By: AngusJust an aside... in some of the early single mode fibres it was found that when you put a really large amount of optical power into the core, the field at the reflection from the far end could break down the glass. This could cause another reflection, and the entire reel of fibre would hollow itself out - 100 m of glass thread with a 2 micron hole exactly down the middle. Weird.

    That is weird, and interesting, and also I just might have an immediate application for this serendipitous technique. I know someone who needs a bunch of microchannels with sharp edges; perhaps some bits of your hollowed fibre could be stacked together side by side in an adhesive matrix, trimmed and end-polished and flushed to yield the kind of structure required. Normal production techniques don't yield sufficient enough uniformity or edge-sharpness in the hole size required.
    100 nm diameter holes would be even more desirable...a special prize for 10 nm holes in a plate 1 mm thick...1 nm holes with nice sharp square edges in a 100 micron plate would get you the keys to the lab...


    Not practical I think, since the residue of the glass is still presumably there.

    However, hole arrays such as you seek are already fairly commonplace in surface plasmon technology. I can't find any full papers for free on the internet, but this might give you a start. Also try the National Institute for Nano Technology in Edmonton.

    http://www.rsc.org/publishing/journals/LC/article.asp?doi=b816735d

    ETA: much of this is of course in metal films on glass. I'm not sure about free standing films, but I'm pretty sure it has been done in either metal or silicon dioxide layers.
  6.  
    Hmm... last time I looked there were various reasons why currently available microchannel plates wouldn't work for this application...I'll have to do some research and get back to you on this topic. Thanks for the links and the anecdote. If you have any pubs specific to that particular phenomenon you encountered with your fibers, er sorry, fibres, could you share them?
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      CommentAuthorAngus
    • CommentTimeJun 20th 2010
     
    Posted By: alsetalokinHmm... last time I looked there were various reasons why currently available microchannel plates wouldn't work for this application...I'll have to do some research and get back to you on this topic. Thanks for the links and the anecdote. If you have any pubs specific to that particular phenomenon you encountered with your fibers, er sorry, fibres, could you share them?


    Right. Just to point out the edit I just made to the previous post.

    I'm not sure if anybody ever published anything. It was a lab observation at CRC back in the early days. As I recall it made quite a zzzip noise too. But the experiment wasn't mine. I'll check with old cronies.
    • CommentAuthorsonoboy
    • CommentTimeJun 21st 2010 edited
     
    Why would you want to add inductance to such a circuit? I should think you would want a min amount of inductance so as to minimize the time of the discharge (therefore maximizing peak power). I know that the underwater spark experiments I read about that were performed in a navy lab back in the fifties used construction techniques to minimize it. They were getting very brief super high power discharges, absorbing something on the order of some 400 million watts from the capacitor bank, concentrated in a hair thin spark channel about 1/2 inch long.
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      CommentAuthorlegendre
    • CommentTimeJun 21st 2010
     
    @sonoboy

    If I had to guess (I don't, but I will anyway) I'd say that he added a little series inductance to allow the contacts to close before the load saw full current.

    The inductor he described is of a very low value, and it would only present opposition to the highest frequency components of the applied (square) voltage waveform - in other words, it would slow the abrupt rise of the leading edge.

    But what do I know. Not much.
  7.  
    Posted By: legendre@sonoboy

    If I had to guess (I don't, but I will anyway) I'd say that he added a little series inductance to allow the contacts to close before the load saw full current.

    The inductor he described is of a very low value, and it would only present opposition to the highest frequency components of the applied (square) voltage waveform - in other words, it would slow the abrupt rise of the leading edge.

    But what do I know. Not much.


    Right. Generally I wanted as sharp a risetime as possible...generally. But I wanted to slow things down sometimes, for various reasons, like segmentation attempts.
    No contacts. I used an overvolting spark gap, made out of two large stainless-steel bowls epoxied to big wooden dowels, mounted in an adjustable fixture. Think large, facing, half-spheres, with an adjustable gap.
    Yes, I generally tried for minimum inductance, but the system can be tuned for what you are trying to do. For optimum vaporization you want the entire pulse energy dissipated in the first cycle: that is, you want critical damping. If you are overdamped you aren't getting max bang/buck, and if you are underdamped you wind up with charge left on the cap due to circuit interruption during the ringdown, also undesirable. Making everything short and fat and close together minimizes overall induction, and then you can add a bit as I did, looking for wire segmentation instead of vaporization. The damping can be influenced by the size, length and nature of the sample as well as the overall inductance added. Obviously I used big cables throughout for minimum resistance.
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      CommentAuthoralsetalokin
    • CommentTimeJun 24th 2010 edited
     
    Meanwhile, back on Earth...

    My CGEM mount has finally arrived!

    And I can tell one thing already, without even unboxing it: It's not "portable".

    Not unless you've got a string of porters on your star safari, that is.