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I'm still having a problem understanding. Please bear with me. I'm talking about a single photon. No spectrum spread. Consider an excited H atom and a transition from n=3 to n=2. That transition will emit a single photon in the red (656nm) and energy 1.89eV. Correct me if I/m wrong. That photon hits a detector. Please explain why we don't know p and x at impact time. Does it change p at the moment of impact?? Of course it imparts its p to an electron in the detector, but certainly there's conservation of momentum. Thanks!

Quick question that probably has an obvious answer. I was reading Quantum Entanglement and the Loss of Reality by Marcella. Good read. But he insists that quantum particles (including photons) have no physical properties until they're measured. That said, photons, as quantum particles, should obey Heisenberg's Uncertainty Principle. For a single photon, we can compute its energy, hence, its momentum, quite easily. When it strikes a detector, we know exactly where it is. How does that agree with HUP - we seem to know momentum and position at the same time. What am I missing?

Thanks for the references, Robin. Makes sense now. Cheers, James

According to the NASA website: "Light from these galaxies took billions of years to reach us. We are looking back in time to within a billion years after the big bang when viewing the youngest galaxies in this field. The light was stretched by the expansion of the universe to infrared wavelengths that Webb was designed to observe. " So the most distant (youngest) galaxies are at 12.7 B ly away. If we can believe the value of Hubble's Constant (from the Chandra X-ray observatory), it's 77 km/s/megaparsec. At 12.7 B ly away, that gives a recession speed of about 300,000 km/s or about the speed of light. Now, even if Hubble's Constant is a bit wrong, we're looking at red shifts from visible not just to the near and mid infrared. If we see anything with the JWST at 12.7 B ly distant, we'd be seeing x-ray objects (supernovae, black hole accretions). I don't think the JWST would be seeing galaxies and "normal" stars at that distance, simply due to the huge redshift. Is my math wrong? Is the reasoning wrong? Or is it just NASA hype and we'll never approach those distant views with JWST? Cheers, James

Thanks for your interest, Dave and Gina. I can't tell what that vintage scope is. But if the price is right, that's half the battle. I only bid on mine because I was pretty sure it was early 20th century. I like the older scopes - although they may take some time to get back into usable (and pretty) shape. Based on popular request, here are some photos. You can see the screw I'm talking about and the missing finder eyepiece.

I just won a Broadhurst Clarkson scope at a London auction. London, Ontario, Canada, that is! At any rate, it was almost given away - no bidders recognized it for what it was. It's a 3" black tube (brass lens cell) with trunnions to fit an alt-az mount (no mount included). The lens is pristine, and the scope came with one RAS-threaded eyepiece, marked 100X. That said, I'd like to do a bit of restoration. The beautiful black tube is quite scratched, so it needs to be re-finished. Anyone with experience in stripping / refinishing a B-C black tube? What type of lacquer, etc.? The finder is missing two of its four screws which hold it to the main OTA. They're "cheese head" types. Does anybody have any to spare? Finally, the finder is missing its eyepiece end (there are internal threads in the finder tube). Does anybody have a similar B-C OTA who can provide details of what exactly fits into those threads? Thanks in advance for any help you can provide. Cheers, James

We can help stop the madness by signing a petition - https://www.astro.princeton.edu/~gbakos/satellites/index.html Cheers, and Clear Skies, James