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+--- Thread: 2021 QB3 (/showthread.php?tid=2228)
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2021 QB3 - bigmasterdrago - 2021-09-02
Tomorrow night might be a good time to attempt to track down this newly found rock from space. Looks like b4 midnight on September 2nd it will be well placed (high and south) and bright enough to be spotted in mid sized scopes. Great phase angle from twilight (2nd) until 4am on Sep 3. Looks to be tracking thru Equuleus into Aquarius at near 2'/min!
The orbit is somewhat uncertain as there are only 68 observations spanning just two days. Make sure to run the ephemeris from your location as it is passing ~665,000 Km (1.7LD). CNEOS indicates it may be 110m diameter.
RE: 2021 QB3 - PMSchu - 2021-09-02
Thanks, BMD. I checked the NEAs on Aug 31 & this wasn't in the download. I have 2021 QB & QB1, but no QB2 or QB3. You really need to check on these things frequently don't you? I'm downloading the NEAs at Today's Epoch now & updating.
Phil S.
RE: 2021 QB3 - bigmasterdrago - 2021-09-02
Phil, It was not in any of the databases. Could not even find in Horizons but there now. Ended up getting all the elements at https://minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=2021+QB3
It's size jumped out at me. But still a fairly uncertain orbit.
RE: 2021 QB3 - PMSchu - 2021-09-02
2021 QB3 was in the most recent download. It looks promising.
Phil S.
RE: 2021 QB3 - bigmasterdrago - 2021-09-03
I plotted it over a roughly 10 degree track last night from 22:00 local to 03:00 this morning. It was well placed during those hours moving ~2°/hr (meridian crossing midnight) but unfortunately in my most light polluted sky toward Houston/Conroe (Bortle 5/6 in the south). I was able to reach 12.5-13 with averted vision in my 13" so had a chance with the orbit uncertainty <1min. I kept giving it my best shot, coming back to the field over a 6 hour window. The Moon was never a factor.
RE: 2021 QB3 - PMSchu - 2021-09-03
It's moving into Aquarius today, but may be a little brighter.
Good luck,
Phil S.
RE: 2021 QB3 - bigmasterdrago - 2021-09-03
Lesson learned maybe. I was using the finder chart I made with elements from the discovery page (68 observations August 31). This had the rock plotted 2' NW of the position using elements today. There are now 162 observations over a 3 day arc but still with an orbit uncertainty of 6. Had I refreshed/downloaded the latest elements, I may have had a better chance with an averted vision pick up. It was fun looking for it, as I had gotten very familiar with the field in Equuleus/Aquarius. While doing this, I got to revisit a few old friends (M15, M81/82, M13, Veil, Ring, Owl). Lesson learned - use the most recent orbital elements!
There is another opportunity to snag it late tonight into the morning hours of the 4th. It will only be marginally fainter (great phase angle) but moving about half the speed (60"/min). Still in my southern sky and lower than 24 hours ago, moving out of Aquarius into Cetus so light pollution is more of an issue. Again, moonrise not an issue.
RE: 2021 QB3 - PMSchu - 2021-09-03
Hi BMD,
For future reference, which parts of your sky are best/worst for finding these buggers? Mine is best toward the SW & worst toward the NE where I get the Columbus light dome.
The data seems to change so fast that it's really hard to keep up to date. Even the HORIZONS elements aren't going to be reliable with a short arc of observations near discovery.
I wish ST4 would keep several sets of elements over a few day interval instead of just keeping the most recent one. It can retain multiple sets of elements, but apparently not if they're too close together in time. It seems like a triplet set of elements ~6 hours apart could be used to calculate 3 separate positions, then apply some weighting to those results to estimate a better position as the close approach unfolds.
ST4 makes accurate position predictions, but they're only as good as the quality of the osculating elements. When the osculating elements are changing rapidly during the close approach - all bets are off. It's not possible to keep updating the osculating elements during the course of the close approach. It could work if the calculations were only done for the one MP in question.
Perhaps something for a future update. It is a rather niche interest though.
Good luck tonight,
Phil S.
RE: 2021 QB3 - bigmasterdrago - 2021-09-03
My worst sky is from azimuth 140 to 225 up to ~50 altitude. Straight up is Bortle 4 or SQM 20.5ish. North is better. North of Twain's Landing - https://www.lightpollutionmap.info/#zoom=12.00&lat=30.4421&lon=-95.5646&layers=B0FFFFFFTFFFFFFFFFF
Lately, I've been spotting new finds on the CNEOS page that seem not to have elements at Horizons yet.
Yep. Future update when only needing info on a single or set of close rocks. Each step gets a new element set for calculating the next step/position. And then so on, as only need to really take the gravs of several objects into account. Sort of like Horizons does it. With several of the close pass rocks running in the program at the same time and not any others, my old PC might not have to slow down for the steps. Elements get altered very quickly when a small rock is under the influence of the Moon and the Blue Planet. Just calculate them, already. If the only thing we are interested in is a single 20 meter rock for an hour, we only need to let Horizons make a single set centered at that time. But for more, it can become tedious to input.
RE: 2021 QB3 - PMSchu - 2021-09-03
I downloaded the elements for 2021 QY3 because it wasn't on the list yesterday. A download of the single MP from the MPC got me the elements for epoch 2021 Jul 5, so I downloaded the NEAs at Today's Epoch again to get elements for Sept 3. Unfortunately 2021 QY3 will be too faint to observe. You never know what you'll get from the MPC, it seems.
I don't know how accurate an interpolation of positions between two element epochs would be. You seemed to get pretty large differences between ST4 & HORIZONS when the elements didn't correspond, which they won't during a close approach - they're changing constantly. ST4 isn't designed to handle this use case, but it's SO GOOD at making charts.
Oh well, get used to disappointment I suppose.
Phil S.