Why it Pays to run Occult4
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Once again, another very nice event - and it's nowhere to be found on either OW Desktop or OW Cloud. Here's another example of why it pays to run your own searches using Occult4.
Many events now (springtime) are quite low on the horizon (roughly... the star-rich region of Gemini is low in the west, Sagittarius is low to the south-east or south...). Many events are simply "tough", and the short nights don't help. Low and behold, I do an Occult4 search for May 21st UT and find an event involving a 10.1 mag star, and 43 degrees up (in the SE)!!! Occult 4 gives me an 88% chance. Bingo...... A very nice event. So bright in fact that I set aside my Astrid and took out the QHY174M-GPS which allowed me to capture the event at 50fps and a SNR of 8.6 (still bright at 50fps)!! Nowhere to be found on OW. Yes, I like OW.... but if you Just rely on it, you are probably missing some nice ones. George |
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4 nights later... May 25th UT
Well, a nice clear night, but - again - a near Full Moon in the sky - and no event over a 4.5% chance listed on OW Desktop. Good night to stay in. But wait... I should consult my nightly Occult4 run.... Hmmm, here's an event involving a 10.7 mag Target Star, tho it states I have a 0% chance if I observe from Home. But... if I make a short drive I'll have a 100% chance(!!!) Result -- I did have to do a 15 minute drive and hang out in a cemetery just after midnight to get it... and... the event was only 17 degrees away from the 97% lit Moon (and 17 degrees up from the horizon - just below Antares). But the 12-inch scope easily slewed right to the FOV, and the Target Star was readily apparent - and yielded a good SNR of 3.66 at 30fps with my Astrid.? ...And I had no complaints from the residents. So....., yet another example of nothing decent on OW, but consulting my nightly Occult4 search gave me a rather sure and easy event. George |
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George,
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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?
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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.
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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.
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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.
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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.
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I did get 3 clear nights this week, but no good asteroid events in my 2 week Occult run nor OW.? So I collected pre-nova spectral data on recurring nova T-CrB.? Here's some very early data if anyone is interested--note that the little peak at H-alpha is mostly caused by a feature in my reference star response curve, I need fix that...
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Steve
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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 |
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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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Good point, sorry!
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Steve
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George Viscome
Steve C
