andrew s

Friction heated up the comet fragments until they exploded. Just as a large meteors do in our atmosphere. As you go deeper into Jupiter's atmosphere it gets dense quite quickly. Google "Atmosphere of Jupiter wiki" Regards Andrew

I am sure it will but with our weather exponentially may be over optimistic! Geometrically move likely 😃 Regards Andrew

Ditto - Regards Andrew

The more expensive complex eyepieces work well with fast optics as the are designed to manage the steeply angled light rays over a wide field. With a reasonably slow Newtonian and possibly a Barlow or Powermate it will be less challenging for the eyepiece. There are some types of expensive eyepieces specifically designed for the planets e.g. monocentric e.g. http://astrograph.net/TMB-Supermonocentric-Eyepiece-10mm . Regards Andrew

I am planning to move my kit overseas. Any recommendations for the best way to access the Windows 7 PC securely over the internet? It is likely to be on a local LAN. Thanks for any ideas. Regards Andrew

Sorry I was not trying to subvert your topic. Regards Andrew

I went to see 2001 A Space Odyssey with Miss Ely at what was then the Cambridge College of Arts and Technology while doing my A levels . At about the same time the young Jupiter was rampaging through the inner solar system. I know an exaggeration but not by much. Regards Andrew

Cue also sprach zarathustra . Regards Andrew.

Fully support getting him there not sure about the return. (Only kidding) But it is not science it's just posing and being a celebrity. I know I am being a science snob! Regards Andrew

Bit too much BC enjoying being on unnecessary locations staring into the distance for my taste. Some good real images. Regards Andrew

I put this to SX and here is the reply from Terry "Yes, electrons per ADU is universally used to define the output of a CCD after A-D conversion, but it’s an ‘after the process’ gain, not the gain of the variable amplifier that CMOS chips include. In CMOS, there is a ‘gain factor’ applied before A-D conversion and this is defined in terms of 0 – N decibels (typically 0 – 40dB). This amplifier gain can be set in software, so we define its gain as unity when giving the base value of readout noise. It isn’t the same thing as the electrons per ADU that is often quoted in specifications. However, I agree that we need to be a bit more specific in our data sheet. Regards, Terry" Regards Andrew

While I agree it has long been the case that CCD gain ( actually inverse gain) has been given in e per adu. This is the term used by James R Janesick who pioneered CCD use in astronomy. See "Scientific Charged Coupled Devices" by JRJ. Regards Andrew

@Adam J I am glad that is now resolved. We can all rest easy 😊 Regards Andrew

Here is the reply from Terry Platt of SX a direct cut and past. It is a closed Yahoo group so you would have to join to see it. "Hi Andrew, I’m not sure where they get their numbers from, but they are clearly incorrect. The first fact to note is that Sony do not list the read noise for any of their sensors, so the chip manufacturer isn’t a source. The second fact is that we measured the noise at around 2.9 and 3.1 electrons on two cameras. The third fact is that even ZWO list this chip as giving 3.2 at unity gain (unity gain is at 0dB) – here is their graph: I think that your correspondents are assuming that unity gain means maximum gain, where the read noise does fall to near 1 electron – but that isn’t what we are quoting in the specification. Max gain greatly reduces the full well depth and is not desirable for many purposes. All the best, Terry" The link to the graph was missing so I have asked Terry to post it again.

Then I see no point in your reply as you just repeated what has been said before. I was pointing out SX seemed to be giving a real world figure and speculating why it might be different to others. You never commented on this just repeated the "fact" that the chip did not have 3e read noise, maybe it does with the different clocking? Who knows. That's why I have asked SX. Regards Andrew

So you think SX are deliberately exaggerating the read noise but why could it possibly be in their interest to do so? Regards Andrew s PS I have asked on the sx yahoo group why the difference in gain.

I have been pondering why SX would quote a higher figure for read noise than their competitors. I have had several SX cameras and as with all new cameras I measure the gain, read noise and dark current along with checking the linear range. In all cases the SX figures are in agreement with their quoted specs. Several thoughts come to mind. It could be the measured value ex camera rather than ex chip or just quoting the chip manufactures figure. It could be the effect of the custom re-clocking to remove/reduce amp glow It could be a gain error. If you naively measure the gain (as I did on an ASI16000) you get a result about 1/16 of the manufactures figure as the former is reference the 16 bit camera output and the latter the 12 bit A/D output. Not mutually exclusive but I suspect that if SX is true to form they are giving an honest figure for their product. Regards Andrew PS Why do magazine camera reviewers not do the same measurement? They are simple and require no special kit.

But who remembers the fun they had with their new toys on Top of the Pops🤣 Regards Andrew

Hi @Olly, I better understand your view now. I think the issues you raise have existed for along time but are asked in new terms as the theories advance. Its a new shore but the fundamental issues remain. What is or not real, is space or time illusory , is this the only universe. You can trace these question throughout the history of science, philosophy and religion. I don't think science can answer them. My own view is reality just is. It does not care if we like the way it works or not be it me you or Einstein. Boltzmann might have a view on quantum theory being the first case of probability in science. Don't get me wrong I see wonder and unanswered questions but for me they are of two types. Ones of detail and complexity or (like your examples) of philosophy and metaphysics. None the worse for that. Regards Andrew

Ok at @Olly, we will have to agree to differ. I don't find relativity or quantum mechanics strange, amazing and powerful yes strange no. I suspect it is a matter of familiarity. I accept that with the success of the science of the Industrial Revolution scientists thought science was complete. Maybe I am similarly mistaken but we have now probed the extent of the observable universe and the subatomic at Tev. There will undoubtedly be better new theories but just a Newtons laws work well at our normal every day encounters so will our current theories at the energies we can reasonably muster. Broadly what do you think is unknown? I suspect you will say dark energy and dark matter but we can characterise them quite well and measure their effects as well as say an electron. Regards Andrew

Not sure I subscribe to that. Science certainly has built a vantage point from which to marvel at the the Universe from the very large to the very small. However, it has also provided a language, mathematics, in which to encode its mysteries. Like poetry it can be read at many levels. Unfortunately, at the surface pop level, it is all to often presented as magical almost occult with spooky interactions. Leading, I feel, to the view a lot is not known. We know a vast amount about what happens (in this sense not much is left to know, at least in the energy range accessible to us) but science is mute on the why it happens. For that we need poetry and the other creative arts. Regards Andrew PS Consider reading "Paradise Lost" without knowing the Bible well. It would be a good story but much would be missed. So it is with science if you don't have the mathematical tools to behold its creations.

Lots of good science but also a lot of extrapolation presented as fact. Cox has finally learnt to let the science speak rather than showing himself off. Regards Andrew

Radial velocity dominates any GR effect. RV causes small shits seen in line positions. You have to account for the motion of the earth but once that is done you can follow pulsations and other shift e.g. material ejection of a stars photosphere. With SN you get both RV shifts and delays due to the metric expansion. Regards Andrew

@vlaivif you want to get very subtle then there is always atmospheric transmission to take into account 🤔

Not sure how important this us to your calibration but in spectroscopy we have to find catalogues with spectra that have not had interstellar reddening removed or if it has apply the reverse transform. If it is important have a look here http://www.spectro-aras.com/forum/viewtopic.php?f=6&t=207&p=2159&hilit=Berardi#p2159 Regards Andrew