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“T CrB can never become a SNIa”
Never is a very long time. Even if the net accretion rate remains negative, the companion star will also eventually evolve into a white dwarf producing a double degenerate system. The eventual merger of such systems could produce a supernova explosion and is increasingly considered to be the cause of the majority of type Ia supernova explosions.
Robin
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
Cheers
RobinThe trouble is that 25lx at street level is often accompanied by vast amounts of light going upwards and outwards. This means that 10km away in the national landscape there is a gigantic light dome filling about half the sky and at least as bright as a local floodlight.
Indeed and this guidance specifically condones this. I can perhaps understand why levels of lighting might vary between zones but cannot understand why they consider higher percentages of upward flux acceptable in more light polluted areas. Table 7 for example makes no sense. Why should 35% upward flux be considered acceptable for amenity lighting in zone E4. I see no reason why the fraction of light emitted upward should not be controlled to the same extent everywhere.
I dont get the idea of zones at all. Good lighting practise is the same if your are in a dark sky site or the middle of a city. This guidance effectively says if you are already in a light polluted region go ahead and put up more crap lighting. (tables 4, 6 ,7)
I’ve also just updated the item on C/2025 A6
month typo in the last line on that page
(we really need a PM button on this forum)
Reflectors in space could make solar farms on Earth work for longer every day. Is this a sensible idea?
https://www.space.com/reflectors-in-space-increase-solar-farm-capacity
Sensible or not it looks like it may be set to become a reality with a demo to be launched as early as next year
https://skyandtelescope.org/astronomy-news/new-kind-of-satellite-could-damage-eyes/NOTE the forum is not attributing the quote correctly. It was from Howard’s post 621451 here
https://britastro.org/forums/topic/dark-skies-and-satellites-in-the-news/page/2#post-621451I very much doubt that anyone here is a kid,
You never know who is eavesdropping though. Google has already indexed this thread
(I see the forum software has attributed the quote to the wrong person for some reason)
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ARGOS ?
I picked up a couple of cheap dumbbells in the Aldi middle isle a good while back. They did nothing for my pecs but two of the weights have been on my EQ6 for over 15 years now. (The hole is oversize but clamping between two standard weight with sticky backed velcro has held them in place.)
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Hi Paul,
ZTF show it as of yesterday at 13.6 g, 13.1 r
https://alerce.online/object/ZTF25abbgajqCheers
RobinA comparison of the current spectrum with one in the low state March 2024
https://britastro.org/observations/observation.php?id=20250810_221150_5f858c960a245997Cheers
RobinSo no detectable gas. (The positioning of the label in fig 2 indicating the band where CN should appear is unfortunate. At a casual glance it looks like the hot pixel there is a signal. Given that they took 6 spectra it is surprising they did not remove them)
Proper motion confuses the heck out of some of the bots auto reporting transients. They compare the sky with their library image, looking at the differences and once the proper motion moves the star out of the psf of the library image it suddenly triggers a bright transient ! There are quite a few examples in the Transient Name Server
If you look at the image cutout at SIMBAD
https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=ZZ+PSc&submit=SIMBAD+search
and blink between the DDS and SDSS images you can actually see the position move between the two survey dates. The J2000 position is between the two (Sometimes for high proper motions you even see a double image Red/Blue in the colour DSS images because of the difference in dates)An ApJL preprint on ArXiv today presents events for the probable direct imaging of a lower mass companion of Betelgeuse:
There’s an excellent episode from the BBC World Service “Science in Action” programme on this
https://www.bbc.co.uk/programmes/w3ct6yfm“Have we found Betelgeuse’s ‘Betelbuddy?’ An astronomical mystery seems to be solved as the long-predicted stellar companion to the bright star Betelgeuse has been detected by a team of researchers led by Steve Howell of the NASA Ames Research Center using the Gemini North telescope in Hawaii. Steve discusses this breakthrough alongside astronomer Andrea Dupree of the Harvard Smithsonian Center for Astrophysics, who has discussed the predictions of this star on previous Science in Action programmes.”
Here is some further information from Alexander on the spectroscopy side which I have been asked to also distribute to the wider spectroscopy community. It is similar monitoring to that requested by Paul Roche which covered mainly 2018-2021 and was reported on the ARAS and BAA forums
https://www.spectro-aras.com/forum/viewtopic.php?t=2128
https://britastro.org/forums/topic/request-for-monitoring-of-x-per————————————————————————————-
Call for Spectroscopic and Photometric Monitoring of X Persei (4U 0352+309)Observers are invited to join a monitoring campaign on the Be/X‑ray binary X Persei, which is currently in an unusually low X‑ray state.
The campaign is coordinated by Alexander Salganik, PhD researcher at the University of Turku, Finland, whose work focuses on the Swift/BAT X‑ray light curve of the system. Since 2001 X Persei has shown three major X‑ray outbursts roughly every seven years. The next expected outburst has not occurred, and the source now sits at its lowest X‑ray flux in more than twenty years. Optical monitoring will help determine the current state and physical properties of the Be star’s disk, including whether it remains present or has dissipated during this faint phase.
Spectroscopy: priority is high‑resolution Hα (6563 Å). Additional coverage of He I 6678 Å, He I 5876 Å, or Hβ 4861 Å is welcome. Target cadence is one observation per week.
Photometry: UBVRI is very welcome. If limited, R and V bands are most useful, with R particularly sensitive to disk emission.
Data can be sent directly to Alexander Salganik (alsalganik “at”gmail.com), who will provide regular feedback and campaign updates.
The paper is now in A&A and a press release from University of Warwick
(At one point there was a possibility of me appearing on BBC Midlands Today but it was pushed off the list by other events !)
Cheers
RobinI am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though.
Transmission gratings are not sensitive to polarisation so that is one thing less to worry about 😉
https://www.edmundoptics.co.uk/f/transmission-gratings/13496
Cheers
RobinOne thing you could do without having to calibrate is to compare the spectrum of the antitwilight sky with that in different directions. Just divide the two spectra to see the difference (Adjust the exposure so the intensity is similar to reduce problems with non-linearity of the camera and be sure to switch off any automatic colour correction in the camera).
Note though that some reflective gratings respond differently depending on the polarisation which changes depending on the direction in the sky. This is an example of the response of a reflection grating. S and P are for the two directions of polarisation. You can also see why you need to consider the grating response as well as the camera QE if you want an absolute flux calibration
https://www.optometrics.com/assets/M466Sales.pngI am not sure if the transmission grating (grism) used in the direct vision spectrograph you are using is sensitive to polarisation though. This shows typical curves for some transmission gratings but it does not show any effect of polarisation.
https://www.optometrics.com/assets/ARTx.png
The one in your spectrograph will probably be similar to the 600l/mm curveCheers
Robin
