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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
Every time I image an 18th magnitude star for variability or capture a 17th magnitude nebula, I wonder at how things have changed over the last 30 years.
I enjoyed visual observing before neck arthritis stopped play, but these days I get a kick out of what we can do via imaging.
I remember looking at long duration photography in the 80s and thinking I would be really smug if I reached 13th mag with my 8″ Fullerscopes Newtonian and some Tri-X. Its a 1sec exposure with a modern CCD.
Thanks Paul for your congratulations to the team. They have indeed done a great job.
I quite like your suggestions re. the ‘non-traditional satellites’, but, before that, I’d recommend a better treatment of Uranus and Neptune. These are far more observed by amateurs now than they were, and we can monitor features on them. They deserve a tabulation of data similar to that for the other major planets.
David
Vice-Presidentyou can get to 13th mag with a Seestar now
True, but a Seestar can do much better than that. An image in the gallery show a 17th magnitude galaxy which required only 11 minutes on a SS50.
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.
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?
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
Thanks Nick for those tables of Uranus and Neptune data. I think exactly those would be useful to include. Central meridian longitude tables would probably occupy too many pages, and anyone involved enough in observation of these planets will know how to get these data from WinJUpos anyhow.
If it had too many more pages the Handbook could no longer be stapled as one unit of folded A4 and would have to have a glued or ‘perfect’ binding, which some would not like, as it could make it harder to keep open flat.
Nick: my thanks also. I am in full agreement with David on this one. 2026 edition perhaps?
Note that these two would be cost-free from a pages point of view as the charts would no longer be required.
Does “one unit of folded A4” translate into 4 pages of handbook (double sided, folded in half)? If so, two more sheets should cover Deimos,
Oberon, Umbriel, Ariel, Titania and Triton and at least couple more selected from Phobos, Phoebe, Miranda and Nereid say.Yes 4 pages of the Handbook are one sheet of A4.
I don’t know the exact maximum number of pages that can be stapled. The printer can tell us, but the other printer who quoted couldn’t do more than 100 pages, so we must be close to the limit now at 120 pages.
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.
Nick: undoubtedly so.
To be honest, I had never noticed but then, I’m not a planetary astronomer.
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.
Closely related: proper motion already affects my code which attempts to match Gaia data to historical positions. A surprisingly large number of stars have moved more than 2″ since 1950. One day I really must download the PM data too and do the job properly.
As space is short in the page limited Handbook, could thought be given to removing pages 117 and 118? Surely its pretty much unchanging from year to year and readily Googled? I think I used the pendulum equation once as a teenager.
Similarly, as a space saving/creating measure, could the line spacing on page 116 be changed? That might free up ~1/3rd page that could be used for some small item like expected dates of observable Earth flyby/gravity assists.
I also wonder who looks at the Bright Stars info page. Genuine question: who uses it?
BTW none of this should be taken as criticism. A huge amount of work must go into creating the Handbook and I for one am very grateful to those who put in the hours. As a result of their work I’ve already started to plan my 2025 observing year. Its good to see the Handbook evolving. Thanks to all involved!
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.
As space is short in the page limited Handbook, could thought be given to removing pages 117 and 118? Surely its pretty much unchanging from year to year and readily Googled? I think I used the pendulum equation once as a teenager.
Similarly, as a space saving/creating measure, could the line spacing on page 116 be changed? That might free up ~1/3rd page that could be used for some small item like expected dates of observable Earth flyby/gravity assists.
I also wonder who looks at the Bright Stars info page. Genuine question: who uses it?
BTW none of this should be taken as criticism. A huge amount of work must go into creating the Handbook and I for one am very grateful to those who put in the hours. As a result of their work I’ve already started to plan my 2025 observing year. Its good to see the Handbook evolving. Thanks to all involved!
You’re a better man than I, Gunga Din.
I also think that we could consider pruning some of the present material but didn’t mention it for fear of the likely backlash and argumentation over what could be removed and what must be kept.
I have never, ever, used the bright stars information. Similarly for those pages mentioned.
+1 for Earth fly-by and gravity assists.
Nick: I’m on your side. However, in my opinion it will be a courageous decision to be made and on a par with the recent re-definition of what constitutes a planet.
I think it would be useful to squeeze D(S) into the Saturn ephemeris in addition to D(E) because not only would it show when rings were backlit but also indicate appearance of shadow on planet disc.
Given quality of imaging produced now also Rhea phenomena and maybe eclipses for other major Saturn satellites.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.
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