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The word “inconsistency” has negative connotations which don’t apply in this case. Each section can decide how it wants to make its material available. In the case of the Comet Section I get and share observations with groups around the world and contributors to the Comet’s Tale are a mix of members and non-members. For Journal reports I do prioritise observations made by members and most of the images I use to illustrate those reports will be from members. Where appropriate I encourage contributors to join the Association to support the work we do.
I’ve posted an animation of some of the C3 frames from today here:
https://britastro.org/observations/observation.php?id=20250114_211401_cc96625da78ff2ec
Yes, the comet is looking very healthy at the moment. Hopefully it will put on a good show for southern observers when it emerges into a darker evening sky.
The public LASCO images have overexposed the comet. Here is the same image taken from a level 0.5 FITS file and processed more gently. It is a spectacular tail.
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That’s not quite fair on the robots!
The first link refers to SN 2023tyk which went all the way to spectroscopic confirmation without human intervention:
https://www.wis-tns.org/astronotes/astronote/2023-265
The second link is to AT 2024agoh which is a transient candidate with no spectroscopic confirmation. Certainly whatever AI/ML algorithms they are using needs to be a bit smarter and check more catalogues.
Give it time and AI will take over the world. Our current government certainly thinks it is our saviour.
If it is clear tomorrow (Sunday) morning and you can get to somewhere with a flat SE horizon it is worth trying to pick the comet up. It rises around 40 mins before sunrise at 51N and, given that it can be imaged in the daytime, it should be reasonably easy to pick up using a camera. From here (Chelmsford) it will be 6deg altitude at sunrise around 8am. My forecast is clear until 5am but then cloud.
Visual observations will be much harder but please report if you try.
Yes, it is. I imaged it this afternoon in daylight from Chelmsford:
https://britastro.org/observations/observation.php?id=20250111_181128_a9e9cf292d6b6418
The elongation was less than 8 degrees so you need to be very careful.
Thanks for the reminder Tim. At 2am it was -3C out at the telescope but I was indoors in the warm. I got videos of the Merope and Alcyone events. From Chelmsford these were at 02:02:23.40 and 02:43:40.95. Lunar occultations of bright stars are always fun to watch.
Yes, if you’ve every been there the big public car park is close to all of the TV antennas on the right of that shot. It is then a fairly short walk to the 100-inch dome.
This was Mount Wilson a few minutes ago. I think that is the Hooker dome and the Solar Tower to the left.
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It’s very close to Mt. Wilson Obsy as well. Hopefully it won’t be another Mt. Stromlo. The damage caused by the various fires in very familiar places around LA is immense.
I use this 100Wh Li-ion battery pack to power my portable setup:
https://www.amazon.co.uk/dp/B06Y5G3C8Z
It only weighs 0.5 kg and it has 5V USB and 9V regulated DC outputs and a 12V unregulated output direct from the internal cells (which I think are LG 18650s). 100Wh is small enough to take on a plane as cabin luggage but it is large enough to power an AM-3 and an ASI camera with cooler for > 5hrs.
Since the 12V is unregulated it drops below 11V at around 50% capacity so I use an in-line DC buck converter to boost the raw voltage to 13.8V. With that, the AM-3 and camera are happy through to around 90% discharge. You wouldn’t need that if you are using the 5V or 9V outputs.
Martin – Here is Saturn for 2025 with DS included. We should be able to squeeze this in next year’s HB. The combination of DE and DS nicely shows the period between the end of March and mid-May when we see the unilluminated side of the rings. Unfortunately this will be very hard to observe since Saturn is at conjunction on March 12.
The 2025 HB is the first one to use my ephemerides for the planets. I think everything is correct but I’d appreciate comments if anyone finds any errors.
I foresee a very vigorous, not to say rancorous, debate over whether J2000 is kept in perpetuity or whether we move to J2050 within this decade.
Historically celestial coordinates have been defined in terms of the Earth’s mean equator and orbital plane at a particular epoch but we now have the ICRF which is based on VLBI measurements of objects in the distant universe. The ICRF is supposed to be completely decoupled from the Earth’s rotation and its motion but its coordinate axes are (almost) aligned with J2000 for convenience. Adopting a new epoch, such as J2050, would break that close alignment so I can’t see it happening.
Given that (most) people seem happy to decouple civil time from the Earth’s rotation I don’t think that it is a particularly big deal to do the same with equatorial coordinates. Anyone who needs to can precess a position to any date they want and the benefits of having a fixed celestial coordinate system significantly outweigh the drawbacks.
It so happens that, as VLBI measurements get more precise, it seems that there are still some dependencies on the Earth’s motion in ICRF (secular changes in aberration due to our motion around the galactic centre for instance) so we haven’t quite managed to eliminate our Earth-centred view of the universe from the celestial coordinate system as yet.
One more thing to ponder for next year. All of the positions given in the solar and planetary ephemerides are of date whereas the positions given for asteroids, comets etc. are J2000.0. In the old days, positions of date were useful for finding planets in the daytime using setting circles but I don’t see that they are particularly useful now. Should we change the planetary ephemerides to use J2000.0?
There is an interesting discussion about whether the standard epoch will ever change from J2000.0 now. With the removal of leap seconds, civil time has been decoupled from the rotation of the Earth so why not decouple celestial coordinates as well? If that happens keeping positions of date might be a good idea.
The PDF version of the 2025 Handbook has just been released.
I am very pleased to see so much information about exoplanets, asteroids, minor planets and KBOs. It’s only quite recently that BAA members have wanted to make (and able to, for that matter) detailed observations of objects fifteenth magnitude or fainter, or which vary in brightness by less than 0.02 magnitudes, and it is good to see them treated in detail.
If there was one category in which I would wish to see more, it is the non-traditional (for want of a better term) planetary satellites. Saturn has been well treated for decades, but how about adding Deimos, Himalia, Oberon, and Triton to give just one bright satellite of the other planets? That is not a reason to neglect Pasiphae, Phoebe, Ariel, Umbriel, Titania and Nereid and their cohorts — though I noticed that the first of these gained an honourable mention in the occultations data.
My congratulations to the team who produced these sections.
Paul
If you need ephemerides for planetary satellites the MPC is a good source: https://www.minorplanetcenter.net/iau/NatSats/NaturalSatellites.html
David – I produced the planetary ephemerides for the 2025 HB and would be happy to do some for the outer planets too if people thought it was worthwhile. Attached are Uranus and Neptune for this year. What things would be interesting to include?
Paul – I suppose limiting mag depends a bit on your skies and a lot on other things. Using a RedCat 51, so the same aperture, from here on a good night a star at 16.0 G has an SNR of 6 in 10 mins using a cooled sensor (ASI2600MC). That is with a sky background of 18.1 mag/arcsec^2. In the same time, in similar conditions, on my 0.28-m SCT I can get similar SNR for a star of mag 20. That’s about right given the ratio of apertures.
Alex – Thanks for pointing that out. My thanks to Helen Usher who worked with the VESPA team to help them link to our comet image archive. This will certainly make amateur images of comets more visible to the professionals.
Yes, Google Earth is probably best. The lat/long in Google Earth is WGS84 and its georeferencing is accurate at the few metres level over much of the UK (mainly the flat bits since projection on mountains is much harder). A few years ago I checked this for my telescope using a surveying SBAS/GNSS receiver which, ultimately, is cm level accurate in WGS84 if you leave it long enough. The position it got was around 1.5m from the position I read from GE and about 6m different in height although I couldn’t work out which geoid reference it was using.
For most astronomical purposes, apart from very precise astrometry of near objects and meteor triangulation, you don’t need that kind of accuracy. In any case, at the metre level you need to be very careful what system you use. Lat/Long is generally WGS84 but height depends on the exact reference geoid and, for instance, the GMN meteor camera network uses EGM96. I think the difference between those two can be 10s of metres (height) in some places.
