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About BiggarDigger

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    Astronomy (obviously!), IT (work - ugh), electronics and radio engineering, meteorology, fresh air and wide open spaces.
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    Biggar, Scotland
  1. BiggarDigger

    46P Wirtanen and a treat

    A back garden session this evening with my 200p Dob. Started around 20:30, though I had a false start as clouds came rolling in. I went back inside for a warm cup of tea and a blether with Mrs Digger. Permission was granted for me to return to the garden at around 2130 and the clouds had melted away leaving a clear sky from horizon to horizon. Seeing was fair to good: I could easily split the Trapezium in M42, but couldn't identify the E&F stars: possibly it was too low in the sky and a lot of disturbed air in the way. Up to M1 and then round to M33 as a double check that seeing was ok. So back to my quarry for the evening. 46P should be located close to the star 94Cet, so star hop from Menkar down to 94Cet and a fuzzy blob appeared close by, roughly centered within in a group of three mag 7-8(ish) stars. Looked pretty much like a galaxy except with the tail which was just visible with averted vision stretching out north and east. After spending a happy few minutes on the comet I swung over to Ursa Major and M109 was an easy catch, then up to M81 and 82, plus NGC3077 and then back round to M31, which I never seem to be able to get away from, it's just such a beautiful object. I could make out the extended disk of M31 and seeing appeared to be improving, so I had a shot at NGC404, Mirach's Ghost. Well, there was certainly something there and in the right place. I never really expected to be able to see in the glare of Mirach, but there it (or something) was. Trying my luck, I went back to Cetus and thinking "Well, if I can see a mag 12 galaxy next to a mag 2 star, I might be able to see a SuperNova"! But, no, it was not to be. M77, Cetus A, was accompanied by a mag 11 star but no additional dot where the supernova should be. I suppose it was cheeky of me and a bit of a stretch for an 8 inch dob. I did however catch NGC1087 and NGC1085, the former like a feint fuzzy blob and the latter an elongated barely brighter patch of sky that caught my eye in averted vision else I would not have seen it. Time for one last look at Wirtanen 46P. Hang on a minute, it's not where it was. I stepped back from the eyepiece and checked with both the viewfinder and the Telrad, yes, I was on it and it not some other object:. In the course of about an hour it had moved to the east and was no longer within the triangle of stars but clearly quite a bit east of them. More than that, as I checked and double checked the viewfinder and Telrad I see a feint grey smudge by naked eye. Looking ever more closely by naked eye at this patch of greyness, I'm fairly convinced it was the comet. Similar in size and brightness to M31 by naked eye; perhaps a little fainter and with a decidedly north-south bias to it's shape. There'e nothing else nearby that would present itself in that form: not an open or globular cluster, nor any nebulae that I can find. I'm pretty sure it was the comet, by naked eye! Cold and more than just a little content, it's time to come in and warm up.
  2. BiggarDigger

    Leonids: initial meteor scatter results

    Sorry for replying to my own post, but it's worth an update after collecting further data from the 20th and most of the 21st now. The morning of the 20th showed what appears to be a similar, if smaller double peak and this morning was pretty much back to a normal early morning single peak. Here's my updated heatmap, again not filtered for duration: The extremely long duration bursts continued well into the morning of the 20th. I noticed earlier this month that I was recording some strikingly long duration bursts, which were wrapping the Spectrum Lab display, so I stretched the display out to two minutes on the morning of the 14th. I'm glad I did, because here's a couple of charts of maximum and average duration from midnight on the 13th (each horizontal tick is an hour): Based on the recorded events at my location the the peak was broadly spread across the 19th and 20th. However, and this may be a big caveat, assuming the duration of the event is somewhat proportional to energy of the strike and therefore somewhat proportional to the mass of the meteor (assuming the velocity is roughly constant across the range of meteors), on the whole larger, more massive meteors were recorded on the morning of the 20th rather than the traditional peak of the 19th. There's some pretty big assumptions in that statement, so I'm not making firm scientific claims based on the data, but it's interesting nonetheless. I've not had time to convert the duration of events into seconds on those charts so they are recorded in cycles of the Spectrum Lab algorithm, where 1 second is roughly 10 cycles. Another interesting item to pick up is the event that ended at 11:56 on the morning of the 17th. This was recorded as being 1978 cycles long (roughly 200 seconds) before it stated to fade - but even then it had a further 20 or so seconds of weaker scattering fading in and out of the capture range of the system. Further long duration events occurred through the peak across the 19th and 20th with many events over 100 seconds and a couple in excess of 150 seconds. Most of these wrapped round the extended window I had set to record, e.g. that super long burst of 17th Nov between approximately 1153 to 11:56: A pretty amazing shower: perhaps not the storm that some people expect from the Leonids, but wow, those long duration bursts! Looking forward to some decent strikes from the Geminids now. Richard
  3. BiggarDigger

    The Tropics of Scotland

    ....But they need to get lucky and be here on one of the three days a year it's not raining!
  4. My initial results from last night's shower show an interesting double peak, with an unusual dip between 3am and 6am, where I would have expected the peak to occur. I also recorded some incredibly long duration events too. This is my heat map recording all events in November up to this evening. It is not filtered for duration, so there will be a little background noise, but should be pretty representative. The gap on the morning of the 14th is a poorly implemented Windows update, where I had to go to work before it completed. There's a peak in activity early in the month, which I'm uncertain of the source. The Northern Taurids appear to be well defined on the early morning of the 12th and the Leonids appeared to be building nicely with a similar early morning peak. Early this morning however appears to show a drop in the count and duration. It wasn't particularly bad weather, in fact it was fairly clear I think, so we should have had no dampening effect due to tropospheric absorption/scattering. Although there was a noticeable drop in meteor count, there was some extremely long bursts during, including during the quieter time. Duration here is in seconds, and yes there was a couple of bursts approaching 2 minutes: Given my range and northerly direction to the main beam from GRAVES these long duration events are unlikely to be related to tropospheric ducting or similar. It will be interesting to see the results from the tonight and then look forward to the Geminids. Richard
  5. BiggarDigger

    Meteor detection - is my kit suitable?

    Adding further to Ian's has post above, a transmitted SSB signal has, not only one sideband removed, but also the carrier. To be able to demodulate (hear the audio in this case), you need to re-inject a carrier wave. In an SSB receiver, this is done by injecting a Beat Frequency Oscillator (BFO). Here's an article that explains a little about SSB https://www.electronics-notes.com/articles/radio/modulation/single-sideband-ssb-basics.php An AM receiver does not have a BFO and, without that, an AM receiver will not, as Ian noted, be able to resolve or demodulate the carrier waver from the GRAVES radar. In theory, a narrow band FM receiver will produce DC impulse directly from the FM demodulator caused by the initial Doppler Shift. However, in reality this will be difficult to extract as it is applied to the audio stages by capacitve coupling to filter out DC impulses. You may hear clicks from a narrow band FM receiver, but these will not be of much use the downstream signal processing. An alternative, and one that is not at all expensive is to use a Software Defined Radio (SDR). Most contributors here use these devices and they range in price from around £20 to a little over £100 on eBay or elsewhere. My own installation uses an RTL-SDR, which is limited in bandwidth and sensitivity, but is perfectly adequate for meteor detection. Generally speaking the more expensive the SDR, the more bandwidth, sensitivity, software compatibility and features it has. If you go down the route of an SDR, consider if you'll use it for other things in the future to make a judgement about cost/performance. For the antenna, you don't need wideband (frequency), but may wish to consider the beamwidth and rear & side lobe suppression to reduce any interfering signals. As discussed elsewhere in the forum, at our lattitude (I'm located near Biggar), we need to look as close as possible at the horizon to receive good reflections from GRAVES. Those further south are able to elevate the antenna if necessary. Richard
  6. Very interesting! I had a quick look through some of the recent October long duration events logged in the database and have some detections at the same time. I'm interested in submitting results from my setup. Are contributions automatically submitted, or sent by email? Given my more northern latitude compared to the other contributors it would be very interesting to compare, especially with a few major showers due over the next couple of months. Richard
  7. Indeed I have. @ajk For receiving sites in the North, the reflection medium appears to be in a different geographical location than for colleagues further south. The signal strengths are somewhat variable and are, at least in my experience, more greatly affected by troposhperic anomalies too (aka the weather). This is as a result of relying on forward scatter from the reverse lobes of GRAVES at 144MHz rather than backscatter from the presumably much stronger frontal lobes of the array. Unfortunately, I have no first hand experience on detection of reflections from BRAMS, but the mechanism should be similar. I saw your note in the other thread about developing your own detection code. That'll be excellent if you're successful. I see from your profile that you have experience in software engineering: it's a big task without that experience as you need to interface with the audio subsystem and build FFT algorithms to be able to process and filtering the data (there should be suitable FFT libraries around I would think). Please do keep us updated on progress. Richard
  8. BiggarDigger

    Meteorscatter using GRAVES

    I think you've got several things in play here, most of which are good. There appears to be groundwave signals being received before and after the strike. There's a significant hook from the head reflection almost buried under the 16:29:35 time line (which is a good indication that it's a meteor rather than aircraft or some other object). There are horizontal spikes appearing above and below the centre frequency during the decay of the plasma tail. I believe these are caused by the FFT algorithm aliasing when the GRAVES radar switches antenna array causing a step change in the received signal strength. There is a "double trace" occurring during the decay of the tail. I see this a lot on my long burst detection, but I'm unsure of the mechanism. I've read that GRAVES is running a single carrier waver, and your groundwave detection appears to confirm this: so I don't know if the "double trace" is an FFT alias (unlikely I would have thought as it doesn't occur all the time on my detections) or if it's some other reflection mechanism. I typically see this "double trace" when the tail reflection is "noisy". I don't recognise it from my amateur radio meteor scatter operation in the past and I don't know what is represents. Overall, I've seen all the artefacts you have in this trace from here in Scotland with the exception of groundwave and agree with Neil. It looks a good solid detection. I've recorded a few bursts today and saw a lovely visual Draconid meteor last night while out with the scope, but didn't record this one at 16:29. However, my geometries will be very different to yours. Richard
  9. BiggarDigger

    Get Triton

    I was out last night and spent some time on Neptune. It's relatively low in the sky just now and although the sky was beautifully clear, seeing wasn't ideal. I think this might have been due to the weather gathering over the horizon to the west. I was unable to spot Triton. 120x on my 200p dob was as far as I could push it with the conditions. Maybe next time. Richard
  10. BiggarDigger

    Meteorscatter using GRAVES

    At 50MHz, meteor reflections should be stronger, if all other parameters are the same, as you'll know about from amateur radio Mike. I think BRAMS is the go to source at that frequency. I assume it's operational, but have no aerial to cover that band to confirm. Even so, it may be too close to you to be useful. Perhaps a 6m beacon in Southern Europe may be a good source? Spectrum Lab is a bit obscure at first when trying to get to grips with it, but is very capable. Good hunting, Richard
  11. BiggarDigger

    Meteorscatter using GRAVES

    Looks good wxsatuser. I used to run 144MHz MS and EME 20 or 30 years ago years ago, but family came along and I had other priorities. With an antenna that size and gain located in West Sussex, you'll likely hear the direct signal which will make the weaker meteoric reflections less easy to differentiate. If I interpret your traces correctly, they do indeed show the groundwave as well as some scatter signals. The beamwidth will be quite small as well, so the area of the sky that you're covering will be smaller than perhaps is ideal. I'm not familiar with the program you're using. Quite a few people here use Spectrum Lab fed from an audio source. Spectrum Lab has a scripting language available to it which allows the program to be automated, logging meteor detection and writing wav and jpg data to file. You're lucky to have the Icom 7100: that's a nice piece of kit. I use a simple Software Defined Radio running from a HB9CV mounted on the side of the house at about 3 to 4m. Far from ideal for weak signal work, but it's proving quite effective detecting meteor scatter from GRAVES. If you have the opportunity to use a lower gain antenna, you may be pleasantly surprised. Richard
  12. So, what have we established? 1. There appear to be non-trivial rear facing lobes radiated from the GRAVES radar site. 2. These rear facing lobes contain suffient energy to produce forward meteor scatter signals detectable far beyond the northern horizon of the backscatter signals generated by the main "southerly pointing" lobes, even with a modest setup. 3. The topic and understanding of both the mechanics and physics of meteoric reflections of radio signals is complex. 4. The data we have to hand is only partially complete. 5. Neil wants a beer. I'm off to read that article...and maybe have a beer too.
  13. It is strange that the vast majority exhibit this falling frequency hook. My traces above show a handful of increasing frequency traces, but they a far outweighed by the classic profile of a falling frequency "hook". What I have noticed, though it is somewhat anecdotal is that the traces of reflections with increasing frequencies are not mirror images of the more classic decreasing frequency head echo. The (rather poor) examples I posted yesterday are however an indication, at least from my site, that these anomalous reflections are far weaker on average than classic decreasing frequency reflections. In my examples, you have to zoom in and almost squint to see the increase in frequency, though it may be easier if I were recording at higher speeds. Is this an indication of the need to have a particular geometry in order to cleanly detect the head echo? I'm going to speculate about a 3rd element that may be missing in your model Ian. The 3rd element being the decrease in velocity as the meteor enters the atmosphere. Your model and charts look good for constant velocity, with the reflecting media moving toward or away from the source/receiver. But what effect might there be if you add in the reduction in velocity as the meteor follows that path? If the velocity is reducing as the reflecting media is moving toward on end or the other, would that result in a net increase in the resultant frequency as a result of combining all the shifts? In other words, is it a multi dimensional problem? Lastly on this line, it's even more confusing that one of my traces looks similar in nature to the traces that Steve posted: where the start of the tail (the portion of the reflection generated by slowly dissipating ionization trail) increases in frequency and then stabilizes to a steady frequency. I've read about high altitude winds moving the ionized gasses at 100's of metres per second but if that's the cause we should expect to see the evidence throughout the tail and on both these anomalous reflections and more classic reducing frequency reflections. Sorry, I may just be more confused than at the start! Richard
  14. Possibly, yes! I'll see if I can find an example of my rare but increasing frequency traces. Richard /edit, so these are some very quick finds where there appears to be a very small increase in frequency before the tail. Note these are all weak signals, not like to more normal ones: A record of two strikes: the first with a very small increasing frequency head and the second with the more normal decreasing frequency: and a very peculiar one that I have no explanation for: and finally a more normal trace from today:
  15. That's rather curious Neil. Have I understood your description: By positively shifted, do you mean the frequency of the head echo is increasing before the long tail trails out in time? If so that's opposite to the majority of my recordings. I do see quite a few with very little or no discernable Doppler which appear to be similar to so called underdense reflections. I see a very small number of reflections where the head echo frequency is small in magnitude and increasing, but the majority of my recordings are where the head echo frequency is significant in magnitude and reducing at very high speed. If I've not misunderstood your description of your positively shifted scatter, I wonder what causes that? Off the top of my head, could it be because I appear to be receiving forward scatter off the rear lobes north of the radar....could you be receiving predominantly backscatter from South of the array, and if so, would that account for a reversal in Doppler shift compared to my reflections? Ahh, sorry, I assumed it was a different model. Yes summing the two curves should result in a symetrical zero point. It looks like there's an offset in the green curve. Richard

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