robin_astro

3 hours ago, Elp said:

Doesn't visible light also shift into infra red over more distance? Hence another reason why JWST infra red camera's are picking up more detail than Hubble.

It does but not at this distance. Here we are looking nearby at a nebula in our own galaxy so no  cosmological redshift.

Cheers

Robin

I took part in Pro-Am studies (using spectroscopy to better define the orbit) during the wind collisions that produced the last two of those rings 🙂

https://ui.adsabs.harvard.edu/abs/2011MNRAS.418....2F/abstract

https://ui.adsabs.harvard.edu/abs/2021MNRAS.504.5221T/abstract

The next dust production episode is due November 2024

Cheers

Robin

The coordinates given are for the supernova. The offset given is from the "centre" of the galaxy, the coordinates given in the catalogue for the galaxy eg for SN 2022pgf in NGC5894 as in SIMBAD

https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=NGC+5894

to the supernova coordinates in TNS

https://www.wis-tns.org/object/2022pgf

ie  from 15 11 40.9482635976 +59 48 32.047254360

to 15:11:41.900 +59:49:12.29

Cheers

Robin

Radio astronomy is a big field and It depends on what you want to measure. In your reading up have you come to a conclusion about the sort of kit  you want to build?  wavelength, size of antenna etc?

If you are looking at a relatively modest 21cm Hydrogen setup for example this thread gives an idea of what is involved and some of the pitfalls. (Spoiler alert, the setup ended up significantly different to that at the top of the thread)

21 minutes ago, wimvb said:

These cameras will need to have good cooling to work. The longer the wavelength, the more interference from heat and the higher internal losses.

The other problem for deep sky work is the sky is pretty bright at these sorts of wavelengths from atmospheric OH airglow (see plot at bottom here)

https://sites.bu.edu/murdock-hart/airglow/

I already see it in my faint object spectra above ~7000A (examples on pages 8/9 here)

http://www.threehillsobservatory.co.uk/astro/ALPY200_VdS_BAAVSS_poster_2014.pdf

but it gets much worse beyond that

Cheers

Robin

It has now been imaged by HST and resolved into four lensed components

from
https://www.wis-tns.org/astronotes/astronote/2022-196

Cheers
Robin

Saw this from NW Cumbria while out waiting for the Moon Uranus occultation. Picked up directly south and followed for about 5-10 seconds, lowish and almost parallel to the horizon as it headed to the west. The firework descriptions are very apt, just like a Nov 5th rocket. Slow moving for a meteor, initially orange, then brightening to blue white before disintegrating, at least partly

Cheers

Robin

This graphic shows the small  shifts in wavelength and changes in intensity of spectrum lines as RR Lyrae pulsates during its 13.6 hour cycle. The Doppler velocity measurements have been integrated to show the changing size of the star and the changing intensity of the lines tracks changes in temperature. These are compared with the changing brightness.   (Unlike what some incorrect graphics  around on the internet show, maximum and minimum brightness do not correspond to maximum and minimum diameter) 

More detailed notes on my BAA page here

https://britastro.org/observations/observation.php?id=20220907_220530_9acdefe378f91ae9 

Cheers

Robin

3 hours ago, inFINNity Deck said:

the downside is that it costs light 

No it doesn't. It just distributes it differently.  Rescale the image eg by binning and (other than extra read noise with CMOS cameras) you will be back to where you were

Cheers

Robin

Here it is tonight

40x 20sec  C11+reducer ATIK428

Cool to think this is a single star (an exploding white dwarf) at ~4 billion light years (comoving distance)

Cheers

Robin

An interesting potential opportunity to see a supernova at 0.35 redshift, further than would normally be possible with typical amateur imaging. Currently at r mag 18.8, it is approximately 3 magnitudes brighter than would normally be expected due to gravitational lensing.
https://www.wis-tns.org/astronotes/astronote/2022-180

Hurry though it is already fading !
https://alerce.online/object/ZTF22aaylnhq

Cheers
Robin

3 hours ago, robin_astro said:

With data over a long enough time you can generate this sort of chart  without knowing the period in advance eg using software like Tonny Vanmunster's Peranso

For fun I ran your data through Peranso without knowing the period in advance and it came up with this.

Pretty close to the published period and light curve shape on the AAVSO page

Cheers

Robin

Sheliak (Beta Lyrae) is not your run of the mill eclipsing binary though. There is an interesting page on it on the AAVSO site

https://www.aavso.org/vsots_betalyr

and the spectrum is monitored by amateurs as part of the Pro-Am Be star survey program.

http://arasbeam.free.fr/?lang=en

A company originally set up by amateurs to make spectrographs is even named after it

https://www.shelyak.com/beta-lyrae-shelyak-2/?lang=en

Yep both primary and secondary eclipses are clear. With data over a long enough time you can generate this sort of chart  without knowing the period in advance eg using software like Tonny Vanmunster's Peranso

https://www.cbabelgium.com/peranso/

Cheers

Robin

1 hour ago, robin_astro said:

Have you tried folding your data? (Shuffling the points back by multiples of 12.944 days so the the values all fall in the same orbit?)

This is easy to do for example in Excel by converting the date-time to decimal days, dividing by the published period and getting the decimal part by subtracting the TRUNC function to produce the phase. Look out for  the primary and secondary eclipses. I just tried this roughly with your data.  I suspect  you might be quite pleased with the result 

Have you tried folding your data? (Shuffling the points back by multiples of 12.944 days so the the values all fall in the same orbit?) You should be able to pick up the shape of the light curve during the period. Alternatively there are programs which can analyse the data to find any periodicity  but I am not sure if there is  enough data to do that successfully.

Cheers

Robin

4 hours ago, Ed astro said:

Another way to display the changes is by plotting a heatmap of all the spectra

Impressive work again !   I used a similar technique to generate  the image in my avatar (but from data at a much higher frequency )

https://britastro.org/observations/observation.php?id=20100825_230000_95356e4359198628

Cheers

Robin

Hi Steve,

No need to patronise me. I am a career hardened  physicist happily living in a quantum mechanical and relativistic universe  😉  

The equipment is just an off the shelf astronomical spectrograph and my measurements were just to test its mechanical stability under different orientations, not to make some profound physical insight. I saw this thread and saw the measurements as an interesting  alternative perspective on the measurement of the speed of light which does not have the difficulties of  round trips or synchronised clocks covered in the article and videos, though it may have other difficulties which we are exploring here (It is clearly a fully one way measurement, no reflection, no return path. The light leaves one end and arrives at the other where the wavelength is measured from the diffraction pattern after being dispersed by the transmission grating. I don't understand why you are still disputing that). 

 According to the measurements, multiplying two independent locally measurable physical properties of electromagnetic radiation, frequency and wavelength gives a constant value, v which  is independent of the orientation.  (The experiment could be made more robust by actually measuring both wavelength and frequency at both ends of the leg rather than assuming the frequency is unchanged. Although this would need two clocks, importantly there is no requirement for them to be synchronised as in the time of flight measurement, just for them to run at the same rate which would be the case for two clocks at rest relative to each other as here, according to special relativity ) 

You offer QED as an explanation as to why this value v may not be the velocity of light and which might be constant even in the case of a universe where the speed of light is different dependent on the direction of travel of the light beam but I have only seen generalisations so far. (The quantum effect of the observer on the measurement and the properties of the grating are spurious here. I don't understand why you would introduce these except to muddy the waters)

I fully expect there is some reason it would give the same result even in a universe where the speed of light is directional  but as an experimental physicist I have the luxury of saying "here are my measurements, explain them 🙂"

Cheers

Robin

8 hours ago, billhinge said:

I don't say the speed of light 'isn't' isotropic so why do you assert I'm a believer of  alternative universes and physics? Proof and belief in assumption/axioms are subtly different

Sorry if I implied this, it was not my intention.  I invited you to demonstrate how a universe where the speed of light depends on the direction of measurement could be compatible with the results of my experiment which appears to suggest that either the speed of light is not direction dependent or as Andrew proposed, space is anisotropic (so the distance between two  objects stationary relative to each other depends on the direction of measurement).  Either viewpoint may be valid as Andrew proposed but personally I would then apply Occam's razor and chose  the simplest solution which is space is isotropic and the speed of light is not direction dependent)

The arguments put forward in the videos in the thread to support the impossibility of measuring c using one way time of flight measurements do not involve quantum mechanics. (Once we introduce quantum effects all bets are off 😉) They revolve around the impossibility of two observers agreeing on a common time, (which is correct and a consequence of relativity) and hence assert that any experiment to measure the speed of light must involve a round trip leading to the conclusion that the speed in each direction cannot be independently determined.  There is an important difference however between my experiment and one and two way time of flight measurements. My method uses one clock (The frequency of the light) and a unidirectional light beam (lamp, transmission diffraction grating, camera rigidly mounted in line, a fixed distance apart)

You can see the apparatus I use (an astronomical grism spectrograph with a built in calibration lamp) here 

https://www.shelyak.com/wp-content/uploads/Alpy600Demetra-510x320.png

The question I pose is why would this measure the same wavelength of the light independent of the direction it is pointing in if the speed of light is direction dependent ?

Cheers

Robin

5 hours ago, billhinge said:

I can (and most others do) measure the square mass of a neutrino to be a negative number but we choose to say the error on the calculation is just enough to to make it a small positive number and hence not an imaginary mass when square roots are taken. This was my final year grad project study on radioactive decay many years ago, neutrino mass being an easily calculated by product based on conservation of momentum. But it wasn't a direct neutrino mass calculation.

That is a "straw man" argument, irrelevant to the discussion here. What you are talking about there is experimental uncertainty. It is in principal possible to measure the mass of the neutrino (and possibly will done be at some point in the future) The assertion made at the top of this thread was that it was impossible in principle to determine if the speed of light was the same independent of direction since it could only be measured in a round trip.  I offered a way that it could in be measured one way (in principle and in practise to any degree of precision one chose)

Cheers

Robin

4 hours ago, billhinge said:

you are missing the point, sure you can calculate a value for c from other formula such as Maxwells eqns 

No I am not. The original hypothesis at the top of the thread  was that it was impossible to measure the speed of light in any one direction. My method (looking for any change in the diffraction pattern produced by a beam of photons sent in different directions) just uses a clock (the frequency of the photon generated by a transition of an electron between two energy levels in an atom),  a yardstick and geometry.  The only formula is v=lamda*f   which identical to that used to calculate the velocity in the return trip experiment (v = 2d/t) except in my experiment the beam is only sent one way. If the velocity of light was direction dependent the wavelength (as measured in the diffraction pattern) would be different. It is not, therefore the conclusion is that either the speed of light is independent of direction,  or  space is not isotropic such that the measurement of distance is in some way directional, (and in some peculiar way, since the diffraction pattern is produced orthogonal to the direction of the light beam)  You are welcome to formulate such an alternative universe and propose how it may be tested.

Cheers

Robin

53 minutes ago, billhinge said:

You always need a two way trip

No you dont. See my suggestion here (and subsequent discussion) which only relies on space being isotropic.

and continued here

Cheers

Robin

There is also a 9 year old supernova SN2013ej still visible in the JWST image of M74 

https://www.wis-tns.org/object/2013ej

https://www.wis-tns.org/astronotes/astronote/2022-147

Robin

It could be anything eg a foreground object.  First step would be to compare it with archive images though it might be tough to find ones deep enough.  Is there a fits version of the image with coordinates (WCS) so we know where exactly it is ?

This is the possible supernova they claim to have found comparing with archival Hubble images

https://www.wis-tns.org/object/2022owj

https://www.wis-tns.org/astronotes/astronote/2022-145

but at mag 25 in the IR it is unlikely anyone will get a spectrum to confirm it

Cheers

Robin

On 22/07/2022 at 09:13, gilesco said:

"Cows, small or far away?"

Bizarrely in our universe this is only true out to about 1.5 redshift. Beyond that all cows look about the same size or even larger 🙂

https://arxiv.org/abs/astro-ph/9905116v4

Section 6 "Angular Diameter Distance"