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Sheridan – A quick look tells me that from an historical perspective there is only mention of two time-related events happening since 2000 namely European Summer Time Act in 2002, and MSF Rugby to Anthorn switch in 2007. I think more can be written about a few significant changes since then. But that needs some researching to identify what that might be.
Just checked:
The G-band photometric uncertainties in EDR3 are ~0.3 mmag for G<13, 1 mmag at G=17, and 6 mmag at G=20 mag.
In Data Release 2 from 2018 April, uncertainties were ~1.0 mmag for G<13, to around 20 mmag at G=20.
So that is a big improvement!Great excuse to open the champagne – I trust you enjoyed it!
Seriously – I see it is the ‘Early’ EDR3 that is released rather than DR3. Am hoping the photometric data is a big step-up from DR2, which itself was remarkably good. I just heard from the podcast that this will be the case – am thinking of switching to G magnitudes as standard in future work since this is a very good match with unfiltered observations and for comets and asteroids it makes for a very good match. We can always convert to some other photometric system if we know the relevant colour index. Great news.
Object ALCHEMY looks to be too difficult from the UK.
Have looked at all the passes during the coming 10 days and none look to be
practicable.
The sky will not be dark enough for the early evening passes around 16h-17h
and the later ones will be unilluminated and a few ‘000 km distant. They
also tend to be low in the sky.Have you tried flagging this on the <seesat-l@satobs.org> mailing group?
Cheers, Richard
Just checked on the definition – Yes – A kilonova (also called a macronova or r-process supernova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge into each other.
I think the idea that only standard supernovae are where these elements are forged is rapidly going out of date helped by the incredible findings from the new science of gravitational-wave astronomy. It will be especially interesting to learn more about the very early universe and whether scope existed for creating heavy elements by collisions when space-time was much more condensed.
Glad you are looking to go one step further …
Can I just point out about the need (or not as the case might be) to take Bias frames. Professionals do this because lots of people use the same instrument and they all probably want to use different exposure times. For the amateur, I would recommend NOT taking Bias frames. After some investigation, I decided it was a pointless exercise. Better to take a series of Dark frames using the SAME EXPOSURE TIME as your Light frames. A good compromise for a standard exposure time is 60 seconds but that will depend on your mount’s tracking performance.
More important is the need to average a good number of Dark frames (and Flats) so that you achieve a satisfactory SNR. How much SNR you need in the Flatfield depends on what you are trying to target for observation. Say 20 frames of each are a good compromise. Also – Don’t forget to take the Flat-Darks with the same (short) exposure time as your Flat frames. HTH
P.S/ Nick James mentions Comet 29P – you might find you will have to sit on that target for say 30 minutes with your 6″ Cass. to build up enough SNR. Feel free to try.
Thanks Andrew for considering others sharing this initiative.
Like you say, once you go into the nitty-gritty details, it becomes more complicated especially the more people involved!
Kevin Hills has recently been out at the site on La Palma troubleshooting dome problems for instance. FYI: The subject has come up several times at the ‘BAA’ but has never gathered a sufficient head of steam to properly start the train moving along the tracks.
Peter – Thanks for the Lunar Occultation of Saturn images.
The finished set of 4 need to be almost square so I suggest each image also be formatted square.
Something like the appended so that Saturn can be seen at a higher image scale. Have to avoid pixelation so may mean saving at even higher pixel resolution. Details of observer and instrument would go on the inside front cover. But it would make sense to put the UT times in the front cover quadrants.
Yes – I would like to echo Steve’s appeal for an image that might potentially grace the cover of this the 100th edition of the Handbook. As with the Journal, we are looking for something notable. It’s usually in square format if that helps and should not have any person in the picture and preferably be in colour although this is not essential. The theme is often one involving objects in the solar system so one showing two solar system objects in the same view would be good – how about a photogenic lunar occultation of a planet?
Imaged July 16 around 22:00UT with a Canon 300mm lens showing detail up to ~3 degrees from the head of the comet. Took some trouble to generate an accurate flatfield before the clouds rolled in and cut short the session. More details on my Members’ Page. Most of England was clouded out that evening.
Yes indeed, ‘Xilman’ – thanks for highlighting this work as it is a rapidly growing are of opportunity for amateur astronomers.
No need to put an attachment as the PDF link to the astro-ph website opens just fine.
For UK / northern hemisphere observers this is still the ‘off-season’ for transit observations as nights are too short to encompass most of the entire transits plus an hour or more either side of the fade. September should mean we can all have a go at this worthy pursuit especially during the winter months.
Denis – As I was mulling over the Web, I remembered that Hubble had discovered comets and that’s what led me to it. BUT, when I saw the name Donohoe, I have a recollection of you mentioning this fact many moons ago whilst propping up the bar at either a Winchester Weekend or similar get-together. Do you recall that? I wasn’t the only one present with you either!
As to the mounted 16″x20″ photograph, that would be a splendid prize for sure but I think a more deserving and younger recipient should win that item at some future date. In the meantime, a free beer would serve just fine – it may be a long wait yet before we rub shoulders whilst propped against some public bar or other and I can down that beer!
P.S. Yes – I like the webinar format – it works well and Nick had loads of interesting stuff to show and talk about. Well done. I have to confess it’s my first one as a spectator – mainly ‘cos I used my Windows 10 laptop to view it – my main PC has too ancient an OS for it to run Zoom.
Denis – They were both awarded the Astronomical Society of the Pacific’s Donohoe Comet Medal: Holmes in 1893 and Hubble in 1937.
I would like to echo Roger’s message by encouraging would-be observers to go to the website and register your observatory as a future participant mentioning in the ‘Comments’ box that you are an amateur astronomer and that you are joining the BAA Exoplanet Division’s initiative to support the ExoClock Project.
We just need some clear skies now – Haven’t seen a properly clear night since last November!
Thanks David for highlight this close approach.
The apparition is on the list of favourable NEO approaches to the Earth in the 2019 BAA Handbook. It is especially easy to observe from the UK as the object is within a few degrees of the opposition point at a Declination of +13 deg when at its brightest (Oct 27). As such it is visible every evening between now and the end of the month, with it as bright as 12th magnitude from Oct 25 – Oct 28, before it finally heads off to southerly declinations and becomes inaccessible from here in the UK.
As many of us cannot attend the actual meeting, it is good to be able to see people’s presentations as a pdf. Mark Bailey’s looks to have been something of a tour de force – an excellent and comprehensive piece of work on his part.
Good point Stuart.
Since Bennu is located between 0.9 AU and 1.4 AU from the Sun, it is in a relatively harsh environment exposed to the solar wind and measuring only about 500m across it has an extremely low gravity. So since it is likely to be billions of years old, there is a lot of time for any dust between the loose assemblage of boulders to be lost. As to the mechanism for this, electrostatic charging is a good one, as you suggest.
One thing to note when looking at the boulders is that they are not like terrestrial rocks since they are very black (4.6% albedo) but more especially the bulk density of Bennu is only 1.26+/-0.07 g/cc. So as there are a lot of voids between the boulders, their density will be roughly 1.8 g/cc on average. This value is similar to the lightest meteorites (certain carbonaceous chondrites have a density of about 2.1 g/cc). My guess is that many of the boulders comprise some sort of porous carbon material mixed with silicaceous grains.
Next year, a sample is scheduled to be taken and the scientists are looking for areas on its exterior where fine-grain material is present and where they can avoid boulders. They have found 4 possibilities:
https://www.space.com/asteroid-bennu-landing-site-options-nasa-osiris-rex.html
Apologies – you are correct – the density of individual pebbles should be about equal to the Bulk Density divided by the Packing Density. So if the Packing density is 0.7 then the actual density of the pebbles would be 1.26/0.7 = 1.80.
Not good to rush from one thing to another on my part. And one should read what one has written before posting! Sorry for that – I will edit the above and put it right.
In fact, my earlier post talked about the angular nature of the pebbles/boulders and the lack of dust particles, and I speculated that one reason is that this could be that the material formed in a relatively high-temperature environment and that it could be rich in carbon including elemental carbon. So having a true density of 1.8 (not 1.0) and being very dark would fit with that scenario.
Mark – I did a search for a suitable asteroid candidate but only came up with 321 Florentina 15th magnitude P=2.87 h Ampl.=0.31-0.52 mag. So there would be a minimum every 1.5 hours or so.
This doesn’t really become accessible until late September / early October. It reaches opposition in December at mag 13.8.
Richard
(3200) Phaeton is one of those asteroid-comet transition objects, so is particularly interesting. I see the article you refer to was the subject of a presentation by Teddy Kareta at the AAS Division of Planetary Sciences meeting last October. I have been corresponding with Teddy on another topic in recent months and am hoping to be a joint author on his latest paper.
Concerning Phaeton, Alex Pratt has recently drawn our attention to a successful occultation campaign to measure its shape. A couple of weeks ago the object underwent a stellar occultation as seen from the USA and we now know that its silhouette measures 5.7 x 4.7 km. See:
http://iota.jhuapl.edu/20190729PhaethonAug09.ppt
It is also on a target list of objects to be visited by the DESTINY+ space probe due to launch in 2022.
