What is the origin of 1LHAASO J0343+5254u? by @hen_edler, @itsMariaArias, myself, @cbassa.bsky.social
Our multi-band analysis suggests that the PWN candidate previously proposed to be its origin is actually an obscured galaxy cluster, unrelated to the LHAASO emission
arxiv.org/abs/2603.03164
The C_d = 2.2 value is the GMAT default, probably to represent a spacecraft with solar panels and the like. I assume using lower C_d values will lower the perigee.
Also, the Apollo 11 Flight Journal has a very good description of the entry procedures using the lift of the Columbia spacecraft that allowed Armstrong, Collins and Aldrin to extend their entry range by about 400 km to avoid thunderstorms. www.apollojournals.org/afj/ap11fj/2...
Three panels showing the altitude, velocity and acceleration of a spacecraft re-entering the Earth's atmosphere from lunar distances. For a narrow range of initial perigee altitudes does the spacecraft skip out of the atmosphere to lengthen the reentry.
Using NASA's General Mission Analysis Tool (GMAT) I simulated non-lifting re-entry trajectories using the default spacecraft properties. A narrow range (~2 km) in initial perigee altitudes yield a skipped re-entry. With lift the spacecraft can control the skip altitude and downrange distance.
It still seems unreal to me that humans will soon be flying back to the moon! They will be returning to Earth at a speed of 40.000 km/h, the fastest ever reentry of a crewed spacecraft.
This remastered video shows a similar reentry from the #Artemis 1 mission back in 2022 at 9x speed. 🔭🧪
I think that such an approach should also work for a re-entry vehicle that can not provide lift, but I must admit I have not seen any real simulations, only my own experience with Kerbal Space Program 😆
Great thread and awesome to see the skip trajectory for real! One thing I never fully understood is the "lift" requirement of such a trajectory. Even without lift, I think one can aim for a perigee altitude where drag reduces the apogee altitude to within the atmosphere, ensuring re-entry.
Aurora above the Dwingeloo radio telescope
Great aurora visible in Dwingeloo yesterday!
An absolutely awesome display of Northern Lights over the Netherlands during the past hour! Red glow in the North and a green curtain passing over whose motion was very obvious with the naked eye. This is 1 hour worth of 15 second exposures with my all sky camera from 21to 22UTC. #auroraBorealis
Yes, this is caused by the Doppler effect.
CarbSAR on S-band.
CONNECTA IOT on S-band.
CONNECTA IOT on 401.5MHz.
Picking up the old hobby of catching radio signals from newly launched satellites. These are 5 satellites from the Space X launch that happened less than 3 hours ago. Signals from 4 CONNECTA IOT satellites on 401.5MHz and 2240MHz, as well as CarbSAR at 2243.333MHz.
Graph titled "Dwingeloo Radio telescope detection of FRB 20251229A". Horizontal time (1 seconds total), vertical observing frequency 1300-1400MHz. A faint vertical line is visible around 210.1 seconds.
Last Thursday, a group of European radio telescopes (HyperFlash / ÉCLAT) detected a flash from the repeating Fast Radio Burst discovered end of December. We also detected this burst!
Our detection came in too late to be included in the telegram, but here it is!
www.astronomerstelegram.org?read=17588
Yes, here it is. Tracking the motion of the planets is a bit tricky, but the motion of the Sun and Moon is very obvious.
You are absolutely right, there are many many ways of visualizing this dataset. I've played a bit to try to visualize the motion of the planets, but nothing good enough yet to share. Hopefully in the future.
A zoom of the 2025 keogram on the end of January, beginning of February, showing the motion of stars and planets.
Indeed, the keogram is the observed version of the S&T almanac. In the high resolution zoomable version at astron.nl/~dijkema/keo... you can even see the motion of the stars and planets. This part of the keogram shows Mars (left) and Jupiter (center) moving earlier in the sky.
Thanks! I hope you were able to capture some cool shots over Christmas! Having an all sky camera is very useful in checking if it is clear enough or not, I can just look at my phone instead of having to go outside and possibly have my eyes dark adapt. If patchy clouds, it tells me where it is clear.
It basically boils down to that while the Moon moves 13deg East every day, it doesn't rise and set about an hour later every day. When it is moving to higher declinations, the rises bunch in time of day and the moonsets spread, while the opposite occurs when the Moon is moving to lower declinations.
Excellent question, and your answer is correct. The keogram is mapped to the 24h schedule of the Sun which shows this hourglass shape over a year. For the Moon this hourglass shape happens every 29 days or so, so this hourglass shape is stretched diagonally.
Ah, I see what you mean now. Yes, that might indeed be possible. I don't know enough about HDR how to make that work though. On the other hand, the camera does support RGGB output as 16 bit integers, so there certainly is room for more dynamic range already in the images.
Unfortunately, taking these observations in HDR would be impractical given the factor 500000 difference in exposure times between day and night time.
No, the gain and exposure are determined from the preceding image, where the exposure time is adjusted first, and gain second. This ensures that 15 second exposure times are used for most of the night and twilight shots, increasing the chance of detecting satellites and meteors etc.
I have tried to explain it in this thread. Let me know if there are questions that aren't answered by it.
bsky.app/profile/cbas...
Show on the Dwingeloo Radio Telescope, against a blue sky.
Snow in Dwingeloo. #bluesky
Well spotted! That is because the Earth's orbit around the Sun is elliptical and the inclination of the Earth with respect to its orbit, resulting in the Sun passing through the Southern meridian early/late depending on the time of year (see the yellow line at 12h). en.wikipedia.org/wiki/Equatio...
A high resolution zoomable version of the 2025 keogram was made by @tammo80.bsky.social, which also shows the motion of clouds, stars and planets from day to day. astron.nl/~dijkema/keo...
See this thread that I just posted, that explains how the 2.1 million images make up the year-long keogram. bsky.app/profile/cbas...
Also check this high resolution zoomable version of the 2025 keogram, made by @tammo80.bsky.social astron.nl/~dijkema/keo...
See also this high resolution zoomable version made by @tammo80.bsky.social for the 2025 year-long keogram. There you can also see planets and the stars in the daily keograms, as well as the direction of cloud movement. astron.nl/~dijkema/keo...
I've tried to explain this in this thread bsky.app/profile/cbas... For each image pixels along a vertical line from (approximately) South to North are taken and concatenated. The 15 seconds cadence is then averaged to once a minute. In the yearlong keogram each daily keogram is averaged to 4 pixels.
This plot shows the exposure time and gain (camera sensitivity) used by the camera for one night, when compared to the keogram for that night. Sunset and sunrise are at the red lines. The camera remains sensitive to colors during evening and morning twilight.
A comparison of the 2024 keogram with predictions for set (dash-dotted line) and set (dotted line) of the Sun (in yellow) and the Moon (in red). The solid yellow line is when the Sun culminates in the South.
For the 2024 keogram I compared the observed keogram with predictions, where the yellow lines show sunset (dash-dotted), sunrise (dotted) and when the Sun is in the South (solid line), while the red lines show the same for the Moon. They match though the camera is sensitive to color into twilight.
