I agree, and that is the point I was trying to make (although probably in a hamfisted and unclear way). The distribution of emulsion flaws was presumably random before the ones closest to the ecliptic were removed.
It wasn't. Villarroel's own data with regard to plate edges strongly suggest that the flaws/"transients" are more dense near the plate edges, though depending on the algorithm, this may be exacerbated by plate overlap. Remember, the graphs of the various sets show the plate grid visually.
This is what I'm trying to work out - where and when is this validation process done, and by whom?
See Solano(2022).
So far, I have found 63 candidate transients, out of 50 plates analyzed. Many more are still being worked on, and I don't expect to have a comprehensive data set and analysis for a long time still. As for that one pic, it is for illustration purposes only; there would be no point in publishing all 63 similar pictures right now. They are for now accessible only to colaborators. Note that that is not even a full-fledged paper, but a communication (or "letter") that I put in place just to, basically, explain to collaborators what the method I used is. The method is designed to find "vanishing" fast transients, that is, something that appears in one image and is not present in another image taken minutes after. It won't find "appearing" transients such as a supernova (unless the processing pipeline is run backwards, with a few tweaks).
You are right that "stars do not have PSFs", in the sense that starlight gets first smeared by the atmosphere, and only then goes thru the telescope optics and is affected by the PSF. Because atmospheric smearing is orders of magnitude larger than the optical PSF (Airy disk, ideally), we astronomers usually do not care about these subtleties, and just call "PSF" the recorded light distribution at the sensor. I guess my wording was affected by the fact I worked for the past 30 years only with space telescopes, where the recorded image of a star *is* the actual point spread function of the optics. I will fix the wording in the next installment of the preprint. Thanks!I find this very sloppily worded:
"While the analysis is ongoing, one notable result is that our findings independently confirm that these transients exhibit systematically narrow full width at half maximum (FWHM) compared to stellar point spread functions."
Stars don't have point spread functions. Point spread functions are a property of the optical system in use. They represent the idealised distribution of how a theoretical point source at infinity would spread light across the sensor. Non-point-sources have their signal convolved with the PSF, but this is a linear function, the smearing of a sum of parts is the sum of the smearings of the parts. I say idealised, as there can be deviations away from the centre of the frame.
img link: https://upload.wikimedia.org/wikipedia/commons/c/c2/Convolution_Illustrated_eng.png
via: https://en.wikipedia.org/wiki/Point_spread_function
If he's saying "these things don't distort through the optics how stars distort through the optics" then that might point to "these didn't come through the optics", surely?
We can always select star images that are not saturated. In the plates I got so far, very few stars are saturated, and these are accounted for by the data analysis software.
There was no other imaging technology at the time. Our challenge is to work with whatever material there was at the time. That's why I love archival astronomy: nothing is easy.
I understand the Palomar plates aren't available because of policy issues. They are seen as irreplaceable assets. The Applause plates might be available for physical inspection though.
Catalog matching was done. That can be tested: three MNRAS 2022 datasets are published here: http://svocats.cab.inta-csic.es/vanish/ Select the list of vanishing objects in POSS I red images (5,399 rows) and perform a cross-match against Gaia and PanSTARRS catalogs using Vizier online service: https://vizier.cds.unistra.fr/viz-bin/VizieR There should be zero matches within 5 arcsec.
As far as I know, they *are* being detected. They are just throw away by the automatic data processing pipelines, or by the astronomers themselves, as the standard explanation for them is space junk. Modern survey observatories like Rubin and Roman will routinely find hundreds on each exposure. That's why it's so important to restrict analysis to pre-1957 images.
They *are* routinely detected by large survey telescopes, to this day. And automatically thrown out as space junk. That's why it is important (from my viewpoint) to study them. If nothing else, they have to be removed so the actual astronomical objects that DO vary in those time scales can be effectively found.
Right, in those days no one even used the term "Schmidt telescope". The focal plane is not accessible from the outside. The Hamburg camera is almost an identical copy of the Palomar Oschin Schmidt camera.
That is unexpected!
