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I have now done a little more analysis of the images taken on 2024-02-16 and believe that I have identified three stars in M45.
The first step was to co-add all the images which did not show any stars and use the result as a flat field. Not having taken any true flats with the i’ filter this was the best I could do. It actually worked extremely well when applied to the images which did contain stars.
It was quite impossible to put a WCS on the images so I examined each for distinctive objects which may be found by comparing with the DSS2 survey. I knew the image scale (0.6 arcsec/pix) and approximate camera angle (-177 degrees) so when a double star was found on image number 47, I could tell that the centroids were calculated as 9.5arcsec apart and at a PA of 225 degrees, the primary being markedly brighter than the secondary. Wandering around the Pleiades I came across HD23964A and HD23964C in SIMBAD and cross-referenced with the Washington Double Star catalog where their separation is given as 10.4arcsec in PA 235 degrees with magnitudes of I=6.74 for component A and (R=9.71, J=8.93) for component C. Very satisfactory!
From that the approximate error in the RA and Dec positioning of the mount could be calculated; it came to about 1 minute in RA and -0.3 degrees in declination.
Another bright star, slightly brighter than HD23964, was found in image number 40. Sure enough 26 Tau, at magnitude V=6.46 and J=5.68, was found well within an arcminute of the predicted position. I am reasonably confident of this identification.
Given how easy it is to pick up 9th magnitude objects in the near infra-red with an exposure where the sky almost but not quite saturates the CCD, I think I’ll try to find some more Messier objects in daylight. Call me crazy if you wish.
The attached images show these two objects.
https://www.mdpi.com/2218-1997/9/9/387 is a fascinating paper. A number of periodicities in muon flux are detectable. A strong signal with a periodicity of 125 days is found, along with a diurnal variation and one which correlates well with the temperature of the Earth’s atmosphere. The global magnetic field of the Sun influences the muon intensity and shows up as a 27 day variation.
However, another variation of about 64 days appeared at two solar maxima (but not all of them). I find this surprising!
Sorry. An OOM error. 60km/600m is a factor of 100, not 10 as given. It makes my argument even more forceful.
Muons have a rest mass of 106 MeV and are created by collisions in the Earth’s atmosphere. Their half-life is 2.2 microseconds, which is 600 metres at the speed of light. From that you can immediately deduce that any muons you detect are travelling fast enough for relativistic time dilation to be very significant. If one is created in the upper atmosphere, at 60km say, the time dilation needs to be a factor of 10. Their relativistic mass increases by the same fraction, so to create a muon in the centre of mass frame requires 1.06GeV. If an anti-muon is also created, as opposed to an anti- muon neutrino, double the energy budget. Now throw in conservation of momentum; the recoiling nucleus will also carry off a chunk of energy.
To the best of my knowledge, very few particles in the solar wind have kinetic energies of well over 1 GeV. I would be astounded if there is any noticeable variation with the solar cycle.
(All figures above rounded.)
The great advantages? Bragging rights to customers and profit margins to suppliers.
Call me a cynic, I don’t mind.
My current favourite is https://arxiv.org/pdf/2403.19937.pdf
I take partial issue with your observation about light pollution being a local problem, for local people. (I note your “fairly” qualification, hence only a partial issue.)
Satellite constellations are a global light pollution issue. Especially if you interpret “light” as “electromagnetic radiation”. The radio astronomers are rather dischuffed as well as those who attempt to observe in the optical.
Totally agree about the (mis)use of “general” in this context. Perhaps sub-fora may be a good idea.
I can’t give detailed advice on the individual packages, though I am sure there are members of this forum who can give advice on choosing which to use and how to use it.
I am a big fan of APT (Aperture Photometry Tool) and have scripts to convert its output into both BAA and TA format spreadsheets. Very willing to provide assistance and the scripts.
My apologies. One of Uranus and two of Neptune. That’s what comes of relying on memory rather than re-checking sources.
My suggestion remains unchanged.
It will have to wait for a few days. The moon is so bright tonight that the sky is very obviously blue and I still have vestigial colour vision in the red-orange-yellow part of the spectrum.
Blue sky at night, astronomers take fright.
Robin: indeed an interesting proposal. I don’t have such a filter but others doubtless do. They are hereby challenged to try it!
I also thought of using a video camera, subtracting a constant level from each frame (the minimum value contained in the frame might work) and then co-adding a goodly number of frames. Again, a constant level would be removed from the final stack.
The sky, being a noisy constant, would be smoothed and reduced markedly but the (again noisy) signal from the stars would be increased relative to the background.
This, of course, is essentially what I do to image extragalactic GCs, TNOs, and satellites in the outer solar system, some of which are markedly fainter than the sky behind them, though rarely are more than a couple of hundred subs stacked.
Hi Joan,
Your first call should be the ARPS home page, https://britastro.org/sections/asteroids where you will find the director of the section is Richard Miles. Contacting him would be a very good idea.
Wayne Hawley is coordinating the observations of several asteroids with the intent of deriving rotational periods. In particular, we are concentrating on 703 Noemi this week as that portion of its phase curve is not well determined.
Rather than give their email addresses here, please send me email directly and I will send them to you. You know where I am!
Paul (J22)
According to Jonathan McDowell (@planet4589 on Xitter):
The Chang Zheng 6 upper stage from the 2021 Apr 27 launch reentered over Hawaii on Feb 9 around 0949 UTC.
The oscillator strengths reflect the fact that transitions are more likely between quantum mechanical states with similar wavefunctions – which give rise to strong lines – versus those with very dissimilar wavefunctions – which give rise to weak “forbidden” lines. But calculating wavefunctions is somewhere between difficult and impossible, and numerical approximation often don’t seem to resemble reality particularly well. Hence the tendency to use empirical lab measurements.
This is bringing back memories.
I am but a humble experimental chemist and know rather little quantitative about atomic spectroscopy, other than hydrogenic systems in the Schrödinger approximation. My DPhil research, was on robvibronic structure in the electronic spectra of Cu2 and CeO in the gas phase. More recently I helped the Exomol team with AlH. A beauty of that field of work is there is a plethora of rotational lines, by and large, and frequently a good number of vibrational bands. Fairly easy to measure the temperature also. With all those measurements fitting a potential curve is not entirely trivial, especially near dissociation, and very difficult when two states perturb each other. However, very accurate results are possible and it is (usually) straightforward to reverse engineer properties such as dipole moment, polarizability and so on. In particular, oscillator strengths — which is what this thread has done to refresh my RAM.
Thank you both.
(BTW, One state in AlH is barely bound and I failed to get a good enough approximatiom to the potential energy curve. Believe it or not, an ab initio calculation was the key to solving this one. It gave a fairly good PEC but a not particularly good absolute energy. The latter was known very precisely from the spectra and putting the two together gave excellent predictions for the oscillator strengths.)
Robin: true.
I question whether it is cheaper to put large structures in space or whether to put large structures (such as transmission lines) on the ground at a range of longitudes.
Or, for that matter, to install storage mechanisms to convert daylight solar energy into nighttime electricity. Batteries, in the general sense of the word, are relatively cheap. Raising a cubic kilometer of mass a hundred metres stores a lot of energy and uses technology which has been well understood and implemented for a hundred years. Melting and re-solidifying a phase-change material, such as NaCl, likewise.
Not obviously cost effective. It’s much cheaper to double the collecting area on the ground than to do so in space.
I’ve seen some where the entire image dynamic range is in the range of 0.0 to 1.0 and that clearly doesn’t work very well if you just truncate.
That is relatively sane compared with some formats I have seen. SWarp, in particular, can generate values which are negative and in a range which bears little resemblance to that of 16-bit signed integers. The result is fully compliant with the FITS standard and, for example, ds9 has no trouble dealing with such images.
That’s why I had to write my own conversion routine.
Ah, the beauty of standards!
It is very important, IMAO, to have a standard. So important that everyone should have one of their own.
Are the files roughly the same size? The raw files you get from the camera are probably 16-bit integer (BITPIX=16). After calibration they may be floating point (BITPIX=-32) and it may be that Vphot can’t cope with that. The FP files will be twice the size of the integer ones. If Vphot can’t cope with FP that is a bit poor but there may be an option in ASTAP to save as ints.
I hit exactly that problem with Astrometrica. To solve it I wrote a Perl script to convert from floating point back to 16-bit unsigned integers. Not entirely trivial because a FP number can be negative and the range can be greater than supported in 16 bits, so off-setting and scaling was required.
David: I am supposed to know what “oscillator strength” means in the context of time dependent quantum mechanics but my memory has rotted in the last 40 years or so and can no longer describe it particularly coherently. Time I ran a refresh cycle on my RAM.
Mark me as recently mystified.
Beside which, I will not be Astrofesting this year.
