This recently discovered, ‘house-size’ Asteroid 2025 KF will pass closer to the Earth than the moon tonight, as reported by Space.com
According to The Sky Live, it is currently at around magnitude 17 in the constellation Hydra. The interactive star map gives updated estimates. My calculations suggest it is moving at around 1/2 degree every few minutes, so I think it should be noticeable against the background stars with a larger aperture.
Closest approach will be around 3:30am AEST, 3:00am ACST, 1:30am AWST.
Unfortunately, it is cloudy in Melbourne at the moment and the satellite images suggest cloud cover across Eastern Australia tonight. Maybe Western Australians may be able to catch this one with a good aperture in the evening before the moon rises?
I would be interested to know from experienced others whether chasing these types of things down for visual observation is realistic. I may not catch it this time, but your thoughts on the best way of approaching these Near Earth Objects would be helpful for next time.
Thanks for the heads up. All planetarium s/w uses a geocentric calculation for planetary calculations that mean that they could be several degrees out up here on the surface! Fortunately those smart people at the Minor Planet Center https://minorplanetcenter.net/iau/MPEph/MPEph.html have provided a web service to get a pinpoint prediction.
Melbourne Observatory is code 908, it saves some time mucking around with the location settings!
It's been a while since I've recorded one, but centre on the precise position and record a few mins of video which you can use to fast forward and reverse to pickup the asteroid amongst the stars. Once you know exactly where it is, its easy to frame properly for a drift through. Here's a playlist of ones I've captured: https://www.youtube.com/playlist?lis...XYjM_OJ_FsbXFi
After browsing Spaceweather, I set up to see if I could record this fast-moving NEO which was predicted to approach within 0.3 Lunar Distances at closest approach.
I calculated this distance to be approx. 115,200 kms or 72,000 miles, a very close approach.
My mount control planetarium application placed this NEO some 5 or 6 degrees off, compared to the JPL Horizons plotted positions, so I went with JPL and it was bang on the target for this 14km fast moving rock.
Tak Mewlon 210, Tak R/F x0.8, ASI2600MM Pro Bin 2x2, single 30 sec exposure.
From the FITs Header in CCDStack:
2025-05-21T11:54:41.076 UT Date Observed.
21/05/2025 09:54:41.079 PM STD Local Time at exposure start.
Exposure 30
Pixel_size_X 7.52
Pixel_size_Y 7.52
Binning X 2
Binning Y 2
From Image Link in The Sky X Pro:
******** ASTROMETRIC SOLUTION RESULTS ********
Center RA (2000.0): 13h 33m 34.69s
Center Dec (2000.0): -28° 25' 57.1"
Scale: 0.7410 arcseconds/pixel
Size (pixels): 3124 x 2088
Angular Size: 0° 38' 35" x 0° 25' 47"
Position Angle: 0° 51' from north through east
Mirror Image: No
RMS: 1.35 (X: 1.11 Y: 0.77)
Number of Stars Used in Solution: 200 (100%)
FWHM: 2.47 pixels, 1.83 arcseconds
*********************************** ************
This attached full res 1280x960 crop from the centre of the frame has been annotated in PixInsight.
Dennis.
EDIT: Added a full frame inverted view showing the trail across 12x30 sec exposures.
…Fortunately those smart people at the Minor Planet Center have provided a web service to get a pinpoint prediction…
…centre on the precise position and record a few mins of video which you can use to fast forward and reverse to pickup the asteroid amongst the stars. Once you know exactly where it is, its easy to frame properly for a drift through. Here's a playlist of ones I've captured.
Brilliant.
I will know how to set up better for next time.
Those silent asteroids look quite ominous on the videos. Thanks for sharing.
Quote:
Originally Posted by Dennis
…I went with JPL and it was bang on the target…
…This attached full res 1280x960 crop from the centre of the frame has been annotated in PixInsight…
…Added a full frame inverted view showing the trail across 12x30 sec exposures.
Good one, Dennis.
Thanks for sharing the photos and the technical details.
The IAU and JPL ephemeris calculators look quite helpful – I will need to spend some time learning how to use them and how to interpret the data. Are there online tutorials?
So, it looks like I need an astrophotography camera to capture these well?
To set my expectations correctly, is there any point to trying to see these visually, or to try to capture one using a standard DSLR?
To set my expectations correctly, is there any point to trying to see these visually, or to try to capture one using a standard DSLR?
This one was a bit faint for visual but you can always practice on main-belt asteroids and track their movement over time - half an hour is often enough to see them move. The close ones are rarely visible to the naked eye due to their small size but 2012 DA14 was naked eye as it screamed by in Feb 2013. I had the immense fortune in broadcasting it's crossing live on NASA TV that night as Australia was perfectly positioned for the event.
I've attached the prediction from here in Coffs, a couple of things to note: It was whizzing by at closest approach, about now actually at over 3 minutes of arc a second! and secondly, as is always the case, it is brightest as it is closes to the sun, not to us.
For rocks moving at a more leisurely pace and maybe 3 or 4 Lunar Distances out, I have found that The Sky X Pro usually puts them in the right spot on my imaging camera.
2025 KF would have been at the extreme end of difficulty to cut your teeth on as it was moving so fast and I believe your positional and time data needs to be accurate when they are this close and whizzing by to minimize parallax errors.
For 2025 KF, I generated an Ephemeris Table via the JPL Horizons website and then selected a time slot some 3 or 4 minutes ahead of the current time.
This rock was moving so fast I selected 1 minute intervals for the Table and the associated RA and DEC coordinates, so I could slew to a time/position combination and then start the exposure sequence.
After slewing to an RA and DEC position, I waited and sure enough, the faint trail appeared. The APS-C sized ASI2600MM gives a nice FOV compared to smaller sized sensors.
Phew!
The JPL Horizons website is reasonably straightforward to use, and you can play about with the various Input Fields to produce an Ephemeris that meets your needs. I keep it simple to Time (UT) and Apparent RA and DEC rather than J2000.
It might be good to practice on one of the slower moving classical Asteroids such as Ceres, Vesta, Pallas, etc. so you can establish a good workflow and practices.
Happy hunting – it can be so much good fun when you manage to locate one of the close approaches.
I find that anything fainter than mag 16 and moving reasonably fast does not sprinkle enough photons on my camera to record a trail.
But, the Sky X Pro allows you to track on the actual RA and DEC motion of the Asteroid, so that the field stars will trail and in this way, I can image fainter NEO’s – quite a cool feature on the mount.
…you can always practice on main-belt asteroids and track their movement over time…
Quote:
Originally Posted by Dennis
…It might be good to practice on one of the slower moving classical Asteroids such as Ceres, Vesta, Pallas, etc. so you can establish a good workflow and practices…
Thanks, both.
This gives me the right place to start.
And congrats to Dennis for making the front page of today's SpaceWeather!
I just downloaded (23/05/2025) the current set of orbital elements for 2025 KF using The Sky X Pro and then performed an Image Link using the image I took on 21/05/2025, then compared the two plots in The Sky X Pro.
“Missed it by that much” according to Maxwell Smart.
The results now indicate a difference of just under 1 degree between the latest plotted position in TSX for 21/05/2025, (purple rectangle), at the time I captured the image, and the actual position in my image (white rectangle) on 21/05/2025, 2 days ago.
One of the Moderator’s on CN wrote:
“Such an anomaly is common once a small body approaches the Earth/Moon system. The strength of our gravity can create significant perturbations in a minor body's path, making orbital elements from even an hour in the past to be approximations at best.
JPL's Horizons, by contrast, solves the multiple-body problem at each step along the minor planet's path, taking the Earth and Moon into account as perturbers”.
The results now indicate a difference of just under 1 degree...
...“JPL's Horizons, by contrast, solves the multiple-body problem at each step along the minor planet's path, taking the Earth and Moon into account as perturbers”...
Location: '34 South' Young Hilltops LGA, Australia
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Quote:
Originally Posted by Dennis
I just downloaded (23/05/2025) the current set of orbital elements for 2025 KF using The Sky X Pro and then performed an Image Link using the image I took on 21/05/2025, then compared the two plots in The Sky X Pro.
“Missed it by that much” according to Maxwell Smart.
The results now indicate a difference of just under 1 degree between the latest plotted position in TSX for 21/05/2025, (purple rectangle), at the time I captured the image, and the actual position in my image (white rectangle) on 21/05/2025, 2 days ago.
One of the Moderator’s on CN wrote:
“Such an anomaly is common once a small body approaches the Earth/Moon system. The strength of our gravity can create significant perturbations in a minor body's path, making orbital elements from even an hour in the past to be approximations at best.
JPL's Horizons, by contrast, solves the multiple-body problem at each step along the minor planet's path, taking the Earth and Moon into account as perturbers”.
Dennis.
When we were trying to catch 2012 DA14, various astro planetarium programs were showing vastly different positions. As Denis said, NASA Horizons is the bees knees. I believe it is the same underlying software as used to predict orbital paths of solar system spacecraft. The other problem for NEO's is parallax. Many astro planetarium programs calculate geocentric positions. Providing you provide your location, NASA JPL Horizons determines topocentric position calculations.
The other one is the IAU Minor Planet & Comet Ephemeris Service https://www.minorplanetcenter.net/iau/MPEph/MPEph.html
Using this service, you can generate a set of orbital elements based on the most recent observations and enter them as a new object in your favourite planetarium software.
I’ll have a look at SpaceWeather as it has ben quite some time since I last submitted an image.
