Forum Replies Created
-
Posts
-
A further characteristic of the Trim-Phone is that the frequency of their tone was exactly in the middle of the ranges where human hearing distinguishes location between sound intensity in each ear and the phase difference of sound waves across the head. Consequently, it was very difficult to work out where the ringing sound (in actuality a warbling) was coming from.
Not only that, blackbirds and starlings loved to imitate the noise which did not help the humans.
Thank ${DEITY} they are no longer common. May they Rust In Pieces.
<p class=”wp-dark-mode-bg-image”>I think I may have captured fragments A & C with my humble Seestar. Here’s a comparison with Nick’s image taken about 35 hours earlier. Image scale is the same. The orientation of the tail is consistent with its motion. Thoughts or an artifact?
Well, I am impressed!
Though I may be an impressionable person.
I have been very happy with the Starlight Xpress CCD cameras I have used. Whether they meet your requirements may perhaps be answered by perusing https://www.sxccd.com/ and links therein.
Paul
I shouldn’t boast but will do anyway. 😉
I am also a co-author of a paper in MNRAS, https://academic.oup.com/mnras/article/479/1/1401/5035837 to be precise.
Beware: unless you know at least a little about quantum chemistry and molecular spectroscopy it will not make very much sense to you. That is why it is quite unsuitable material for me to boast about in JBAA. Doubtless there are numerous members who can say the same thing.
Paul
An excellent meeting, in my opinion. I learned a lot from the presentations and it was good to meet people in person with whom I had previously only communicated over the interweb thingy.
My thanks to all those who put in such hard work in organizing the event.
Paul, I know you are after various editions of Norton’s which I look out for, but none so far. I’ll see what else I’ve got.
James
Back when I was an undergraduate another member of OUAS had a copy of “Webbs Atlas of the Stars”. It disappeared and the erstwhile owner regretted it greatly.
I have always wanted a copy of my own but they are almost unobtainable now. When they do appear on the market the prices are ridiculous — several hundred USD/EUR/GBP — and I refuse to pay that much. I own a good number of atlases, old and new, for which I have paid much less than that.
If anyone has a copy of Bečvář’s Australis at a reasonable price I am also interested. His atlases are already in my possession and I have a spare copy of Eclipticalis if anyone is interested.
I’ll be there with a load of secondhand books for sale, so bring your money.
I am often in the market for old atlases, especially editions of Norton’s not yet in my collection. Don’t know if this will influence your choice of books to bring.
Paul
Measuring stellar proper motions has been possible for amateurs for a long time now, though we will not reach Gaia levels of accuracy.
In particular, I really must update my track of Barnard’s Star with images from this year. Ok, that’s an extreme case but proper motions greater than, say, 100mas per annum should be fairly easy to measure over the course of a year or few.
The pipeline I use is MaximDL for taking images; local astrometry.net using the Gaia catalogue to put a WCS on each sub; SWarp for stacking if required; and then APT for photometry (my primary interest) and initial astrometry (if desired). The source list fed into APT contains Gaia positions and its output includes substantially sub-pixel precision on the stars’ centroids, in both pixel and sky co-ordinates. That’s good enough for me (and I repeat that my primary interest is in photometry rather than astrometry). Perhaps I could, and should, try harder to achieve ultimate accuracy in astrometrical positions.
Paul
<p class=”wp-dark-mode-bg-image”>A test would be to take images with the telescope rotated to different angles (but with the camera orientated the same relative to the horizon). If it is atmospheric refraction the red and blue areas will always be top and bottom relative to the horizon. If it is the telescope, they will move to different angles relative to the horizon
<p class=”wp-dark-mode-bg-image”>Cheers<br class=”wp-dark-mode-bg-image”>
RobinGood point. I wish I had thought of that.
At what altitude was the moon at the time?
The atmosphere acts as a prism and deviates red and blue light differently at different altitudes. The effect is most apparent where the air is thickest — at low altitude.
https://en.wikipedia.org/wiki/Atmospheric_refraction covers the phenomenon but only slightly and could be greatly improved in my opinion. Searching on “atmospheric dispersion corrector” will produce more information and a fair description appears at https://astronomytechnologytoday.com/2017/07/06/atmospheric-dispersion-corrector/ but the available information is far from satisfactory in my opinion.
Paul
1. One-word answer: temperature. The smaller the gravitational field gradient the less likely a virtual particle pair (not restricted to photons by the way) is to be split into real particles and the lower the energy carried by each. As photons have zero rest mass there is no lower limit to their energy, which corresponds to no lower limit to the temperature of the BH. All sufficiently massive black holes have a very low temperature. A solar mass BH, for example, has a Hawking temperature much much lower than that of the cosmic background and is absorbing those photons, thus slowly gaining more mass from them than it is losing from Hawking radiation. The hypothetical observer would see the CBR as being much much more intense than the Hawking radiation which would be swamped completely by the background.
2. There is no good theory of quantum gravity as yet. The naive calculation is almost certainly wrong. Further, Hawking radiation has yet to be observed because all known black holes are far too massive to emit significant levels of radiation.
I love the 112 authors not listed. How many words is that per author?
Is this going to happen whenever the LSST consortium publish?
Astronomy is now reaching the point particle physics reached about fifty years ago.
Big collaborations collecting vast amount of data which requires enormous amounts of computation to convert that data to information.
It is getting that way in biology. I’m a co-author on a few genetics papers published by the Flybase Consortium which have numerous authors, though admittedly not over a hundred.
Welcome to the new world.
<p class=”wp-dark-mode-bg-image”>Y
<p class=”wp-dark-mode-bg-image”>As for all this talk of molten metals: don’t try this at home kids.The important word here is “kids”.
I very much doubt that anyone here is a kid,
5, Make your own. < £20.
If you don’t fancy the idea of pouring lead I’d make one for you but you are in the UK and I am not.
Paul
P.S. Concrete would work as well. Messier, not as dense as lead and takes longer to solidify, but not as hot when wet.
I needed an extra weight for my Meade.
An old metal paint can, a kitchen stove and some scrap lead worked wonders. A wooden stick, well soaked in water, made a central hole which needed only slight tidying before the weight went over the shaft. No fastening screw so it is held between two of the original weights which can be fixed in position.
Acquiring scrap lead is not that difficult.
Cost me nothing but a bit of butane for the stove and 30 minutes of my time. I even found the can discarded on a building site.
I am not a mechanical engineer, but wouldn’t the thread give way before the body of the bolt? I’ve seen far too many stripped threads in my life.
