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I checked CrB on Sunday evening- still no sign of T CrB in outburst. I’ll make a proper observation of it tonight.
Yes, even I put away the pencils and got out the camera!! Two images below taken on my IPhone.
Alex,
You raise an interesting point about what the Met office and BBC Weather class as a clear night. At the time of writing, both of them say it is clear outside (a single moon with no clouds on their websites) and yet at the moment it is at least 85% cloud cover- if only someone from these institutions could go outside and look up to check!
It would be interesting to know their definition of a clear night sky! Satellite 24 indicates a gap coming- we wait and see…
Cheers,
-PaulIt is rather depressing and I can’t recall it being this bad before- I had no clear nights at all in December 2023, and just a few nights in January to April. May so far has been a little better.
Like Gary, I am a visual observer so that don’t need pristine clear skies for observing. My interest hasn’t waned of course, but I have noticed just how poor the Met office is at predicting clear nights. I now use a combination of sources including satellite 24 to make my own forecasts, the official forecasts are simply to inaccurate.
Cheers,
-PaulPleased to report that T CrB is now accessible from my observatory! I shall be keeping a close watch of this star.
I’ve been through my records and overall the weather in Leicester has followed the same general pattern, namely April, May and June were the best months. Unusually November was fairly good but as usual December was terrible with no useable clear nights at all. The couple of clear nights we had in December were unusable due to high winds. Overall I managed 66 observing sessions in 2023- this does not mean there were only 66 clear nights, there would have been more than this but I was unable to use them due to being away. This was marginally better than the previous year.
What I have noticed this year is that the clear nights were very well dispersed by days and nights which were very cloudy and/or wet. Let us hope that 2024 is better.
Cheers,
-PaulHi all,
Interesting discussion. I am a bit of a way from honorary membership, however I can see that it is a nice tradition we should keep to mark the 50 years of someone’s membership. I do think Nick, Jeremy and Gary make a good point about the membership fee and it does seem that younger members effectively pick up the tab.
I suggest we adopt Martin’s suggestion and keep the honorary membership to mark 50 years but membership fees have to continue to be paid.
Cheers,
-PaulI made it magnitude 9.3 this evening! It was quite unmistakable at x38, even though the sky wasn’t completely dark at 1730UT.
How many more times- I am not a cosmologist part time or otherwise! 😉 Seriously though, I am pleased it was a successful meeting and many of the people who attended have told me how much they enjoyed it! As you say the speakers and the venue were excellent and I’m particularly pleased that all of the speakers on the Saturday were experienced BAA members.
My thanks to everyone who helped make the meeting a success- I think we should have definitely have another practical astronomy meeting in the near future!
I just hope it happens when CrB is accessible- perhaps Jeremy can check the delivery note to make sure that it arrives after December?! By the way, will we have some naked eye comparison charts ready?
It’s interesting what you said about a nova getting you interested in variables Gary, my first was the supernova in M82 a few years back- you suggested I do a few variables and now I have over 10 which I follow regularly!
Cheers,
-PaulLooks like the meeting went very well; I was planning on attending but alas the rail strikes on Friday and Saturday made it almost impossible!
Well I’ve now lost it from my observatory so I can guarantee that it will now do something interesting!!
Hi Chris, it’s best to let the meetings secretary (Hazel Collett) know. Her email address can be found in the Journal.
Cheers,
-PaulThere are many subtleties to this but it sounds like you haven’t included the Bianchi identities, in particular the first and perhaps the second Bianchi identities. There are reasons why this tensor has these properties. There are also the anti-skew symmetries and one of them is to do with defining a suitable inner product on the tangent space T(M) which is induced by the metric tensor g_ab.
If a curvature tensor satisfies the skew symmetry, anti skew symmetry and first Bianchi identities then it is trivial to show that there exists a curvature tensor at each point p in M (a pseudo-Riemmannian manifold) which has n^2(n^2-1)/12 components.
It’s all in two standard texts:
-Introducing Einstein’s Relativity by D’Inverno
-The Mathematical theory of Black Holes by Chandrasekhar.Due to cloudy skies I have only managed six observations- the one I made last night is included on the plot. Although it’s only six points it is enough to see the basic type 2 supernova light curve.
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Hi Ken,
I think an deep understanding of the mathematics involved is essential- there are some popular books which give overviews of GR and particle physics but without understanding topics like differential geometry, exterior calculus, group theory and Lagrangian dynamics it’s almost impossible to accurately convey the subjects properly. It’s rather like learning a foreign language by repeating constructed sentences but not knowing the meaning of the words.
I’ve been teaching our General Relativity course at Leicester University which our 4th year MPhys students can opt to take and I would recommend:
-‘Introducing Einstein’s Relativity’ by Ray D’Inverno
-‘A short course in general relativity’ by Foster and Nightingale.Not convinced about a variable Planck’s constant for a variety of theoretical and experimental reasons at the moment.
Cheers,
-PaulThere are indeed other approaches but these are the two main attempts so far, and the history of their developments allows a fairly simple introduction to the area without too much technical detail. In any case, many of them are similar in approach albeit with different wave equations (Dirac, Yang-Mills+gravity, DeWitt-Wheeler) and don’t as yet add much to the general picture I was describing for Ken.
Yes, I am familiar with Wolfram’s idea- I have to say I am not convinced at the moment. I have no issues with spacetime geometry being an emergent phenomenon, nor indeed time being an emergent phenomenon (which I’m sure it is and I wouldn’t be surprised if it has more than one dimension), but as yet I haven’t seen anything which really deals with the problems discussed here or other problems like the violation of unitarity.
cheers,
-Paul
