Forum Replies Created
-
Posts
-
The light curve of some of these objects bounces back though as they redden as the reference I posted shows so it would be interesting to take a comparison image in a few months time
I think we can agree though it has indeed turned out to be a “Potentially interesting transient in NGC 4631″
Indeed, as I already reported
https://britastro.org/comment/10041#comment-10041
I never said it was a supernova and posted the classification as soon as it became available
Cheers
Robin
My current observatory PC is showing signs of age. I normally use cheap refurbished desktops which last typically 3 years before expiring in the less than ideal conditions but this sounds an interesting alternative. How much space is left after a Win 10 pro installation? (I don’t need too much as I offload to a separate server at the end of each run and don’t have any huge megapixel cameras but 64gb sounds a bit tight ?
Thanks
Robin
I remember imaging that with my modified webcam and CCTV camera
http://www.threehillsobservatory.co.uk/astro/astro_image_37.htm
and the spectacular light echo images from the Hubble. I took over where the Hubble left off 🙂
http://www.threehillsobservatory.co.uk/astro/v838Mon_anim.gif
It has now been classified as a probable Luminous Red Nova.
http://www.astronomerstelegram.org/?read=14360
I have to confess I had to look up what that was. Fascinating !
https://ui.adsabs.harvard.edu/abs/2019A%26A…630A..75P/abstract
Robin
That’s a great shot Nick, particularly with that bright moon. (To much haze here. I could not even see the galaxy) It looks like it probably is a supernova then. It depends on extinction of course which could be high given where it is but this might end up being one of the brightest for quite a while.
http://www.astronomerstelegram.org/?read=14326
with what sounds like a better spectrum, confirms likely IIP with low luminosity (-14.5)
ZTF have now called it on TNS as a type II based on a spectrum they took 5 days ago. I would not say their spectrum is over convincing though (A hint of a broad H alpha emission at the galaxy redshift, perhaps with a P Cygni profile but not much else) and running it through SNID does not come up with any high confidence hits. It shows a blue continuum suggesting not much IS extinction so it seems to be very much at the low luminosity end
Cheers
Robin
Well the distance to NGC2268 is probably reasonably accurate as it based on Ia supernova 1982B (which was V mag 13.5 when discovered just past maximum) so assuming this object is say mag 17.5 at maximum this gives it an absolute magnitude of -14.8 There is then 0.2 mag extinction from our own galaxy giving abs mag v mag ~ -15 which is very much at the low end but not unknown for supernovae eg
https://arxiv.org/abs/astro-ph/0112051
but if there is a lot of extinction in the host galaxy it could be higher luminosity of course.
(It could also be a foreground CV of course. We need a spectrum)
It is interesting that there has been no published professional classification yet. Maybe it is something interesting and the classification is being withheld. (Not unknown. Classifications can be submitted to TNS with an embargo)
Cheers
Robin
It looks like it has levelled out, well (~5 mag) short of what a type Ia without extinction would reach
Does this ring preload the taper bearing? If so it should not really be that tight (Just enough to preload the taper bearing by the right amount, hence the use of the grub screws to lock it in place.) Has it been stripped down before and retightened? (These internet strip downs never seem to talk about torque settings which I would have though are pretty critical for precision engineered parts like these)
The slit is 23 microns or 3 arcsec. It normally runs in the Dec direction which is probably the best bet as the star and PSN will lie at different positions along the slit provided the seeing and guiding is good enough to split them. I could just pick up a weak spectrum of the pair with perhaps signs of a broad H alpha emission line which would indicate a type II, though there is quit a bit of that around in the galaxy background as well. No split though (and to be honest at mag 17.9 I would not stand much of a chance of getting a useable spectrum in any case)
This video suggests a conventional right hand thread. (Though it also shows it to be deceptively simple to remove !)
https://www.youtube.com/watch?v=SrvkKjgjbRY
(16 min 30 sec)
Well done for splitting it from the nearby star. I put the spectrograph slit on it but it is so messy round there, it is going to have to outshine the star and galaxy background if I am going to have any chance.
Sorry this is a historical observation from the Digitized Sky Survey plates
Have just been looking at where this field is so I can take a quick look with the spectrograph guider from time to time. Impressed by how bright (and blue) it appears in the DSS image
>That is why I was careful to state that the dynamic range can be improved by a factor of NxN for N-fold post-binning, and not the signal to noise ratio. Sometimes the dynamic range is particularly important, such as when trying to detect extremely low contrast objects for instance.
Indeed and this is a limitation of in camera binning where unlike post binning, you cannot see the individual pixel counts, so to be sure of not having any individual saturated pixels you have to limit the total counts in a super-pixel to the full well depth of an individual pixel.(Well I suppose one could perhaps assume a gaussian distribution of brightnesses in the star image and allow a higher maximum count per super-pixel which would bring some dynamic range benefit.)
The in camera binned exposure could be split into NxN shorter sub-exposures to match the post binned dynamic range without risking saturation but that then returns you to the same read noise contribution as for post binning. In camera binning can be advantageous though for weak signals in a dark background where the read noise contribution can be significant (in spectroscopy at low SNR for example.)
