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Hi Callum,
It looks like another of my posts went astray, this one about 3I/ATLAS. Could you see if it has been wrongly marked as spam please?
This behaviour is very annoying. Can it be improved please?
That is roughly what I was suggesting.The idea came to me when I remembered the image of Halley’s comet which was released shortly before the comet reached aphelion. The stars were subtracted and what remained stacked on the motion of the comet. IIRC, C1/Halley was 29th magnitude at the time.
The idea is testable using images of a star field which is easily measurable before removing all but one of the stars. See whether the before and after measurements are comparable. Repeat with different stars removed and with different fields.
It’s a shame I’ve so little spare bandwidth or I would try it myself with some of my planetary satellite images — of Amalthea, say.
Added in edit: Ah, my earlier response to Nick contained that idea with the suggestion that DAOPHOT’s computed background images be stacked and measured. I know it was posted because I subsequently edited it. Hmmm….
Second edit: Callum rescued it from spam purgatory and it now appears above. Thank Callum.
Paul – I’m pretty sure that the scatter is due to faint stars in the aperture since this is a very crowded field. I think it is far to early to say anything about the lightcurve of this object but the more observations the better. I have used DAOPHOT and it can be very good but I’ve not been able to get it to work reliably with moving objects.
Just a thought: have you tried using DAOPHOT on each sub to remove the stars and then stack the remaining sky background? All that should be left are the very faint objects.
Not suggesting it will give results which are any better but it may prove an interesting experiment.
<p class=”wp-dark-mode-bg-image”>I’ve been doing some astrometry on 3I/ATLAS and have been surprised how much scatter in the magnitude that I’m getting day to day. The plot of magnitudes from MPC astrometry data also shows a huge scatter. This data doesn’t have a consistent photometry aperture or filtering but, for most observers at the moment 3I/ATLAS is a point source so it is surprising. The scatter may be due to measurement errors in the crowded star field but it is worth making estimates of the magnitude if you can.
Might the scatter arise in large part from the multitudinous fainter field stars which are too faint to show up clearly in the images but the photons from which will create a very noisy sky background. The noise will add both to the counts at a given a pixel and will vary strongly from pixel to pixel.
Have you tried PSF-fitting photometry, using DAOPHOT for example? It would be interesting to see whether you get significantly different results. DAOPHOT is famous for working well in crowded fields. It is a shame that using it is often a fiddly pita in practice.
It is interesting that 2I/Borisov was definitely cometary and it looks like 3I/ATLAS is as well. 1I/Oumuamua was not but it did have anomalous nongravs which implies it must have been comet-like.
It is clearly an alien space ship. 😉
I also support this, having imaged several of the Palomar GCs.
While on the subject of GCs it would be nice if one could tag extra-galactic GCs (for example, Mayall II) with both “globular cluster” (term not yet included in the dictionary) and the host galaxy “M31” (already present). Would make finding images of GCs much simpler.
Of course, the same approach would be helpful for other classes of objects, such as “double star” and “planetary nebula”.
Paul
Back when I was a teenager we saw an Elephant Hawk Moth caterpillar walking along the garden path. It was the size and shape of a perambulatory chipolata.
As it was clearly close to pupation we kept it safe until it hatched and then released it.
That was in Derbyshire. Privet Hawk Moths were relatively common on the Oxon/Bucks border. No idea whether they still are.
Richard: the Elizabethans were well practised too and, with the advantage of an additional century of technological development, were able to do so on an industrial scale. Remember DDT? Remember the Camelford incident which is well described in https://en.wikipedia.org/wiki/Camelford_water_pollution_incident where not only were people left with aluminium deposits in their brain, lead from piping was also leached into drinking water? How about tetraethyl lead added to petrol?
Incidentally, and speaking as an ex-chemist, the dangers of Pb poisoning are almost universally misunderstood. Organic lead compounds, such as PbEt_4_ are really, really nasty. A few milligrams will kill you and quite rapidly too. Soluble inorganic lead compounds do pretty nasty things to the CNS. Insoluble lead compounds are arguably helpful — a coating of lead sulphate or carbonate on the inside of lead water pipes which is naturally produced in hard water districts prevents soluble lead compounds leaching out. Metallic lead is virtually harmless, unless injected en masse into the body at high velocity. Many people live for decades with several grams of Pb inside them, especially where the location of the bullet makes surgery to remove it a markedly higher risk than to just let it be.
I’m sure that you as another ex-chemist are well aware of the content of the previous paragraph.
Paul
Hi James,
I bidded up the price on some of these and dropped out at the last moment. Should improve the Society’s bank account a little.
In principle you may be able to measure it yourself if you can find another camera with a known QE curve. If you don’t have one to hand perhaps someone could lend you one. Unfortunately all my cameras are in La Palma.
Using the same optical system in front of the detectors and a source of identical brightness, measure the intensity of the spectrum and use one to calibrate the other.
Not saying it will be easy.
Denis: Your S&T collection sounds very interesting.
Perhaps I should explain my reason for wanting to build an extensive library, in addition to loving books and relevant journals. Many people here know that I have an observatory in La Palma. Within the next 15 months or so I will sell up my house in the UK and move to LP, taking my library with me(*). I also want my place to be a self-supporting research observatory, even after I eventually snuff it. Astro-tourism, on-site astronomy classes and visual observing sessions, and remote access to the telescopes will help fund things, as would renting the house to tourists in general. Part of a well-equipped observatory is an extensive library, both historical and immediately practical. BAA members and the BAA as an organization have helped me extend the library greatly in the last few years.
I already have a century or so of BAAH, JBAA, The Observatory, and decades of other journals such as MNRAS. Atlases range from C19 Proctor to the Millennium Star Atlas. A few hundreds of books are also present, from Sir John Herschel to vol. 11 of Annals of the Deep Sky which came out late last year. Around 100 books and a smattering of atlases are already in La Palma. I make sure that I top-out the airlines’ hold baggage allowance …
Paul
(*) Six boxes of journals were packed up and put into storage ready for shipping today alone. Perhaps 30 will be needed for the complete collection.
The latest missive from the Cambridge Astronomical Association arrived this morning. In the current edition of Capella, their newsletter, is a fascinating article about how the sky brightness varies with altitude. The naked eye limiting magnitude was a whole magnitude fainter at 120m above street level! The observations were made from a 35th-level apartment and from the street immediately below in a Bortle 7 and Bortle 8 sky respectively.
https://www.cambridgeastronomicalassociation.com/ for more about the CAA and access to their newsletters.
I’m also pleased not to be the only nutter. These are the editions I do have:
1 (1910)
3 (1921)
9 (1943)
12 (1954)
13 (1955)
14 (1959)
15 (1966)
16 (1973)
17 (1986)
18 (1989)
19 (1998)So more than half!
Thanks,
Paul<p class=”wp-dark-mode-bg-image”>I was wondering if the BAA held any copies of Alan Heath’s autobiography-“Memoirs of an Astronomer”? Neither Amazon, Waterstone’s,nor Summerfield Books (the specialist natural history booksellers) have it. Thanks, Rob Duffy.
I have a copy but not a duplicate.
It could be loaned out to anyone willing to promise to return it and to pay postage in each direction (or to travel to CB22).
Paul
