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A Tale of Three Stations
For last night's 2000 AP126 event, I got aggressive and tried 3 stations.? BLUF:? with a lot of luck, I managed to get 3 positives:
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Bobcat Observatory (home):? +31 km, 32%--had a ~0.3 second positive-->used a Watec 910/VTI on the finder scope of my C-14 (prepoint)
Grand Canyon Airport:? +28 km, 74%--had a ~0.5 second positive-->used an Astrid on a C-5 (prepoint)
Cherry Spring State Park:? +9 km, 100%--had a ~1.2 second positive-->used a QHY 174GPS on a 66 mm refractor (tracked), this is where I was in person
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Tom at Martz Observatory:? +4 km, 100%--might also have usable data
It didn't start well--I wondered into the observatory about an hour before I had to get in the car to work the remote stations with no clue how I was going to do this.? Normally, unattended I get the C-14 on field with a go-to and just let it track.? But this time I had to set up 2.5 hours before event time, the target was so low at this time I couldn't acquire it--plus the event time was right around a meridian flip.? I thought about a C-14 prepoint but didn't like the odds with the small FOV.? Then it occurred to me that my finder (80 mm) would be fine given the star was 8.5 mag (even at 17 degrees elevation)--I've never tried this before.? The f/4 finder would have 4x the FOV.? So I mounted the Watec to the finder, and quickly found the c-mount to 1.25" adapters I had were all too long to come to focus.? After a half hour hunting for a shorter one, I fired up the bandsaw and cut a quarter inch of the length of on of the adapters I did have (I'll clean it up in the lathe eventually--looks pretty ugly right now, and yes I still have all my fingers, but my father would have yelled at me about safety if he saw how I did it!).? Dropped that in, and was able to focus--nice images, good enough limiting magnitude.? Used the mount to prepoint at general field, locked down and verified the prepoint by looking at the star field go by and comparing the what TSX showed--then doing the math.? In the end, this worked perfect--the blink happened when the star was near center.
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The second station at the airport was no drama--the Astrid had me in and out of there in less than 15 minutes.
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The last station at Cherry Spring State Park (our PA darksky observing park) had only minor issues.? I had the NextStar mount set-up and aligned very quickly.? Took me a bit of time to convince myself I was on the right field (too many stars!).? QHY's GPS wouldn't do anything but say "Bad Data" initially, but once I cycled SharpCap off/on it came up fine.? Unfortunately, right before event time it indicated "Partial Data" and continued to produce times without location.? Hopefully that won't impact the timing data (my hand calcs show the three stations roughly align in time as you expect with their distances along the path).? My last problem there was as I was packing up a car pulls into the (quite large and almost empty) parking lot, goes all the way around, and parks right next to me.? The guy get out, and wants me to explain to him what you can do where in the park--a potentially long discussion.? It is 2:45 AM!? Hopefully I wasn't too rude to him...
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Anyway, my first triple deployment worked out great.? I would even out the spacing more if I was doing it again, but some of that is hindsight.
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Tonight I'll be trying (14965) Bonk.? Weather looks 50/50.
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Steve
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Re: More on Flash Timing - Some testing...
Good stuff, George.
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My comments:
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Steve C
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Re: More on Flash Timing - Some testing...
Great news!
I hope IOTA is developing GPS flashers for sale. I think it will be a great way to get new members in at low cost, if they already have a CCD camera.? I tried the phone app flasher, and had issues with recommending the phone app flasher for new users, but a GPS based flasher should be a good way to attract new members. Rick Bria? |
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Re: More on Flash Timing - Some testing...
NEUS Folks:
An overabundance of cloudy, rainy skies lately so I thought I'd complete the analysis/tests I started a little while ago using my "Aart's Flasher".? Why am I dong these tests?.... I've heard/read several discussions about timing with flashers - with some folks liking the devices and some folks being critical of them. But in all discussions, I can't recall anyone who has ever backed up their statements with actual test results. Well, here's some test results... Mainly I'm doing this to satisfy my own curiosity, ....and sharing the results. Purpose of the Test: To compare D & R times obtained first by using (GPS-based) Timestamps (on every frame of video) as the reference source, and then comparing the D & R times obtained by using two (GPS-based) "Bookend" Flashes as the reference source -- using the same .CSV file. Conditions: As with all flasher tests I've done the "bookend" flashes were put on a video that also contained GPS timestamps (on every video frame). A single .CSV file was generated and that file was used to measure a "simulated occultation" -- first by using the timestamps, and then by using the two flasher "bookends". The tests were conducted under "real sky" (outdoor) conditions by very quickly waving a piece of cardboard in front of the telescope (the simulated occultations probably averaged about 3/4 of a second in duration). The simulated occultation was near the mid-point between the two flashes. A typical time between the 1st flash and the simulated occultation was 45 seconds, and also 45 seconds between the simulated occultation and the 2nd flash. The D & R of the simulated occultation was measured using PyMovie/PyOTE. PyOTE reported a GPS Timestamp error of 0.00% for every test. For the 12 tests listed here, I used my Astrid camera -- so the flash-derived times are a comparison against Astrid's GPS timestamps. The flasher used was a unit made for me and based on Aart Olsen's Arduino-based design. Summary of some numbers for this series of tests (GPS-based flasher against GPS-based timestamps).... * The Average difference between the calculated D & Rs - between timestamps vs flasher was 0.0015 seconds ? (about 1/666th of a second). * The Minimum difference was 0.0001 seconds * The Maximum difference was 0.0034 seconds (1/294th of a second) * In 11 out of 12 tests, the flasher yielded D/R times a minuscule fraction of a second before times via timestamps. I'm attaching scans of the 12 test results. The important number are in the yellow boxes. Conclusions: With these results (and many earlier ones), I would feel confident to record an occultation solely based on _MY_ flasher unit -- as I consider it "proven". I also know how my cameras (RunCam, QHY, Astrid) perform, and they nearly always produced 0.00% timestamp errors. That said, I do feel that any flasher unit must first be tested (numerous times) against timestamped video before any assumed accuracy should be inferred. The camera & recording system used should be proven to not be susceptible to dropped or duplicate frames. Of course, I would always prefer using a system that placed GPS timestamps on EVERY frame of video, and would only resort to using "flash timing" as a last resort (or perhaps for unmannned stations). Just a word of note for anyone attempting their own tests.... Keep the simulated occultation short in duration (1 second or under). Since you will be very briefly covering the entire front of the telescope, ALL stars in the FOV will be gone during the simulated event. Thus you can't use a "Tracking Star" to keep the PyMovie aperture locked on the Target Star during the "occultation". In using a simulated occultation of 1 second or under, the PyMovie aperture will not have time to wander off the Target Star. (And even if it did, it often won't matter since you will be using the same .CSV file in measuring times via both Flasher vs Timestamps. In a worse case, any "wander" may simply introduce an unwanted "fade" in the "R"). Maybe this is of interest... maybe not. George |
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Re: Astrids
Ted reports the current Astrids are completely assembled and have all the parts (except for a power supply and tablet or notebook PC of course!).
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Steve
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Astrids
All,
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Is anyone on this waiting on an Astrid?? I just paid for my second, sounds like it is ready to ship.? The IOTA price, which is I believe "all inclusive" (completely assembled, and I'm assuming includes qualified USB stick, feather for switching modes, GPS antenna) is $695 plus shipping.
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Steve
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Re: (15532) 2000 AP126 Thursday Morning
Tom,
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Great--can you mark you location on Occult Watcher?? Or I can do it for you.
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Steve C
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(15532) 2000 AP126 Thursday Morning
I don't think anyone is anywhere close to this one, but just throwing it out there.? Low in the south at 17 degrees, but rank 100, modestly wide path (60 km) and mag 8.5 with 8.7 drop.? Also 1.6 second max duration.
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Path crosses:
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?Steve C
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Re: Flasher Box Status
George,
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The box design came from John Moore, who is a much better 3D print designer than me.? It looks nice, and fits the board perfectly
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Power connections are on the opposite end from the LED and GPS antenna connectors.? 2 choices for which to use (both available by default) (1) a typical 2.1 x 5.5 mm male cable input with 6 to 12 vdc center positive or (2) a USB-B (old boxy style for most Arduinos, some now have USB-C inputs).? Aart tells me he just uses the USB, so if you have a USB battery, that should work fine.
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The LED uses the typical audio jack (mono), so you can vary the cable length or leave the LEDs on various telescopes.
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Prices look like:
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Steve
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Re: (5361) Goncharov Campaign
Steve:
Re: (5361) I'd thought about it, but like you, it's also about a 4 hour drive for me. If I need to accomplish something else by doing such a drive I'd consider it, but right now... probably not. I wonder if anyone had thought of checking to see if there were a nice event going on while Stellafane was happening this year? If there were that might have been a good opportunity to promo occultations. I'll find this year's Stellafane dates and try to see if a nice event is planned for their Springfield VT location. George |
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Re: Flasher Box Status
Steve:
Nice. Looks like you used an off-the-shelf "project box". Looking at it I see the GPS connection and what looks like a plug for the LED flasher, but I don't see any power connection. What voltage does it use and how are you getting power to it? Did you indeed make it so the lead to the LED flasher can be unplugged from the box (seems like a good thing to do)? I know of a friend in VT who might be interested -- maybe. For a "trustworthy" unit (with a quality Arduino board), what would be a rough price -- the $80 you mentioned (plus shipping)? What would the user need to buy... the GPS antenna?, Micro-SD card (of what capacity)? George |
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Flasher Box Status
Everyone,
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The first flasher box is done (again!)--photo attached.? We had issues getting it to use its SD card due to a change that Adafruit made to their GPS board last summer.? Aart and I went back and forth quite a bit trying to get mine working.? In the end, Aart bought one of the new boards (he only had some of the older versions before this--and be warned there are several--maybe four--versions with the same name if you find an old one kicking around your junk drawer) and got it going.? Once he shared the recipe which only required a software change, I had mine working in a couple of minutes.? Testing is next when I have some time.
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I did find in my junk draw one of the older Adafruit boards--which was also different from all the ones Aart had.? He is pretty sure he knows how to set my old one up, and sent me a "sketch" (Arduino program) that should drive that one.? I bought a cheap clone Arduino Mega ($22) for that one and plan to put it together and print a box for it this week--I have spare parts from the first as most of the smalls (connectors, LEDs, etc) came in 10 or more packs to use.
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Again, if anyone wants one, I can put one together for you and send it in your direction for cost of the parts--of order $50 to $80 plus shipping depending on what Arduino board you want.
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Steve
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Re: Flash Timer
Steve:
I excerpted a portion of your post (below) and am posting a reply under the flasher-related topic.... You wrote...... I now have Aart's latest flasher design working. ?It really would have taken about 1 to 2 hours except for two problems I had--one with how to load the replacement SD library correctly and the other that the GPS shield had a set-up physical switch in the wrong position. ?Both of these can be avoided with some additional words in Aart's assembly procedure (or just having someone a little smarter than me doing the assembly). ?Note that Aart is having me be the guinea pig for his new assembly instructions. ? Now that I've done one, additional units that I could put together would take me less than an hour each. ?I think my total cost has been well less than $100 (somewhere around $90)--but I did spring for the "real" Arduino Mega instead of a cheap clone--that would reduce the cost by about $25. ?If the builder has an old micro SD card, they could save the $10 I spent on that. ?The antenna lead also is likely overkill, potentially saving another $3. ?So the cost could end up being in the $50 to $60 range. ?I did buy multipacks of pots and LEDs--so the remainder of those would be available for additional units as well. ? I still need to design and print a box to hold it, but once I do one, I can either share the file or just print some additional ones for anyone who needs one. ? While I have it running, I still need to learn a bit more about how to use it before I start testing it. ?After that, I am happy to loan it out to others in our area who want to try one. --------- Interesting news! Great to hear you have assembled the flasher and have it working - and parts cost less than $100 (possibly could be built for $60)! Yes, clear assembly instructions are certainly helpful. It often seems folks who are "in the know" on devices like this often take it for granted that a person who wants to assemble one somehow instinctively knows certain things.... which can cause a failure of the project. Clear instructions can make all the difference! --------- You later wrote.... Quick update on the flasher. ?John Moore shared a 3D model of the box for it with me. ?I was able to print it on my cheap 3D printer overnight using a dollar or so in PLA filament. ?His standard LED connector is a 3.5mm mono audio connector which I didn't have. ?I have ordered those, adding about $2 to the total cost. ? Is anyone interested in getting one? ?It was easier than I assumed, and Aart should soon have updated instructions available. ?You will need to do a modest amount of simple electrical soldering. ?Some options where I can help: ? I can print you a box and provide jumpers, LED, pot, and 3.5mm connectors (I bought extras)--just reimburse me shipping plus $3 for the parts. I would be willing to assemble a few, just reimburse me for parts ($60 to $100 depending on "real" Arduino or clone choice and if you have an old micro SD card already) and shipping. ? Once I test mine a bit, I will make it available as a loaner for any new folks who join our group. ?If you know anyone interested, let me know. --------- Ah, it sounds like John incorporated a connection for the lead to the LED! That's a welcome improvement. It allows for the flasher (LED) to permanently attached to the scope and the flasher's box to be unplugged and "removed" when not needed. I've considered doing that mod on my flasher. It's also very gracious that you are volunteering to help in making these available - maybe even assembling one for someone (granted they should cover the cost+ of the parts involved). I know a couple observers that might like a flasher.? This certainly is a route that might lend itself to more chords being observed in the Northeast!!!!! Do show us - (with maybe some images of) - the final unit. Then run some tests against your QHY and/or Astrid (I'll be posting some more flasher tests soon). Flasher's AREN'T the ideal way to time an occultation, but.... In the long run, are 2 chords better than 1? George |
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Re: Why it Pays to run Occult4
Good point, sorry!
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Steve
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Re: Why it Pays to run Occult4
Quick update on the flasher.? John Moore shared a 3D model of the box for it with me.? I was able to print it on my cheap 3D printer overnight using a dollar or so in PLA filament.? His standard LED connector is a 3.5mm mono audio connector which I didn't have.? I have ordered those, adding about $2 to the total cost.
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Is anyone interested in getting one?? It was easier than I assumed, and Aart should soon have updated instructions available.? You will need to do a modest amount of simple electrical soldering.? Some options where I can help:
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Once I test mine a bit, I will make it available as a loaner for any new folks who join our group.? If you know anyone interested, let me know.
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Steve C
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Re: Why it Pays to run Occult4
Steve:
I'll reply to your 1st paragraph / question with this post. More later on the interesting info on your Flasher.... You asked: "Do you feel that running Occult a day or so before a potential clear night gives more events (for that night) than my current method of running it roughly every 2 weeks covering the next month?" Short answer... It depends. But yes, you probably miss "some"..... Thoughts...? * First, if you run a search 2 weeks ahead, there's a small chance that JPL might update the orbit (new astrometry comes in) between the time you ran the search and the clear night(s) you get in that 2 week period. Thus, your path could have a shift that you wouldn't know about. That would be my 1st concern. * Much also depends on how you are setting the criteria (/filtering) for your search - in short, how "deep / wide" your search is. [My std initial Search Criteria is: Asteroids 2km in size or larger = 259,786 rocks, Mag drop >0.15, Mag limit 16.5, Duration >0.1 sec].? In my nightly searches I get an initial filtered output of over 300 events per night (just called one up and it lists 333 events for May 27th). But this is showing filtered events out 220km from me. One reason I search so wide is that it allows me to be alerted to an unusually nice event that might run near other NEUS observers.? [...And of course, when you get an initial listing of MPC-based events, you then have to connect to JPL to get the better JPL-based elements]. Another reason is that there is often quite large path discrepancies between MPC & JPL paths (100km not uncommon). So if I were to obtain initial MPC-based paths only out to 50km or so, then when I re-generate those predictions based on JPL, good events where the path is actually quite near me per JPL (but not MPC) may not show. So yes, using too narrow of a search radius for the initial MPC output may not let you obtain some quite good events that the final JPL predictions would eventually show. Also... If you have the ability to "Go Mobile" (like you and I do), then it's good to encompass a "wide" observation area - at least 100km from Home base. So if I ran a search for 2 weeks (using my criteria) I'd get roughly a filtered list of roughly 4,600 events (behind the scenes my computer would create a list - before filtering - that quite possibly could be over 10X that amount! -- ie., overload). I'd then have to link with JPL and download 4,600 events (Occult4 lists a JPL download limit of 3,600 events). It would "tie-up" their computers for at least 10 to 20 minutes. ...And I know most of the searched nights would end up cloudy anyway. Why use up both your and JPL's computer time searching for nights that will end up being cloudy? As a final step I "re-filter" the JPL-based event list to 45km or so for my own potential events (45km for me in this case lists 70 events per night).? Yes, you can run searches out 2 weeks ahead but that may introduce "limitations". Almost certainly to avoid computer overloads you will have to limit how "deep" your search is. At most I'd run 5 days ahead. Ideally 2 days ahead. 2 days ahead is enough time to be able to make observing plans in advance, and possibly notify others that an event might run near them also. It also somewhat guarantees that the orbital elements are "current". A factor also is how fast your computer is (how long you want to "tie it up" for). FYI, I just ran a search for just one night - June 1st. Using the relatively new, quite fast computer I have, getting the initial MPC-based events took 25 minutes. I obtained an initial list of 431 asteroids after filtering out to 220km. I then connected to JPL and obtained JPL-based orbits (took 4 minutes) for those 431 rocks, and re-generated JPL-based paths. Re-generating took 2 minutes. Result - 366 rocks (that still met my criteria). Total time to get 1 night's worth of good, JPL-based predictions --- under 30 minutes. ?[For 2 weeks that could be 30 x 14 = 7 hours -- providing the computer didn't overload and crash]. George |
Steve C
rickbria22
George Viscome
