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Just to round this off, here is the processed version of Mike’s early spectrum image taken on 2026-08-25 compared with mine for the same night. They are qualitatively similar with the P Cygni profiles in H alpha, Beta visible at this stage can be seen in both spectra along with various other lines including FeII. The objective prism resolution approaches that of the ALPY at the blue end but is significantly lower above 5500A where the non linear dispersion compresses the scale in the prism spectrum. (Note the Y scale, these features are quite weak)
Cheers
RobinAttachments:
Note that the forum software incorrectly attributed my quote here to Gary for some reason (I have seen this on occasion before and could result in some confusion and dispute !)
Nigel Evans has derived the dispersion equation for my system so I can calculate the wavelength for any pixel value in the spectrum.
Hi Mike,
I used a mix of Visual Spec and ISIS to process your spectrum (VSpec to remove the sky background and digitise, ISIS to derive the dispersion equation and rectify) See
https://britastro.org/forums/topic/variable-star-section-circular-for-september-2026-number-209#post-642748
but there are other packages around which could do this eg RSpec, BASS and others. The steps are the same and essentially those I describe here
https://britastro.org/document_folder/baa-document-store/past-talks/spectroscopy-workshop-at-the-nlo-oct-2015
specifically “Low resolution slitless spectroscopy”You still need a reference point in the spectrum to be able to do an absolute wavelength calibration though, hence my question about the possibility of including an image of the star in the same image.
We are off topic here though so we could either continue this in spectroscopy section of the forum or off line if you like
Cheers
RobinNot sure if it can be picked up in Mike’s early spectrum
Yes Mike reported the P Cygni profile was visible, most clearly in H beta
https://britastro.org/forums/topic/likely-bright-nova-in-sagitta#post-642596Cheers
RobinHi Jeremy,
There is indeed an early Star Analyser spectrum of this Nova posted on “Cloudy Nights” in which the P Cygni profile at H alpha is resolved
Note sure if it can be picked up in Mike’s early spectrum but I will take a look (The resolution in prism spectra is highest at the blue end where the dispersion is greatest)
Cheers
RobinI see the “logged in” cookies but they are all set to expire at the end of the session (which is why I am being logged out) while others are not.
I have just edited the expiry time on these cookies to a date in the future and I stay logged in
Robin
If you’re experiencing premature log-out, I think it’s almost certainly due to cookie-blocking software / settings in your web browser which is deleting the BAA’s cookies
Looking at the BAA website cookies when I am logged in I see the “logged in” cookies but they are all set to expire at the end of the session (which is why I am being logged out) while others are not. If I compare with the cookies in Stargazers Lounge for example the similar cookies are set to expire in 3 months. Is this a browser setting or a website setting? AFAIK I have nothing specifically set up for the BAA website for this. Some websites have a feature where you can decide of you want to stay logged in or not. I don’t see that option for the BAA login but I am wondering if it has been set somewhere and is different for different members ?
Cheers
RobinIs that a P Cyg profile in the H_alpha line in the Tessier spectrum but not from the prism?
Hi Jeremy,
I think it is probably an artefact from the spline fit I used to reduce the resolution down to match Mike’s resolution. There was a P Cygni profile at ~1500km/s in early spectra 25/26 Aug but it was soon engulfed by the emission. Here is H alpha in Francois’ spectra at full resolution. You can see the P Cygni profile in the earliest spectrum (and in my low resolution spectrum from 25th) but not after (The narrow lines are telluric water lines)
Cheers
RobinThe spectroscopy database is not designed to take spectrum images and though digitisation is straightforward using freely available software
Here is a “quick and dirty” digitised spectrum off the jpg of the observation 2026-08-31 compared with one from the same night by Francois Teyssier from the ARAS database at much higher resolution so spline smoothed for this comparison.
For wavelength calibration I used a 4th order polynomial based on 8 identified emission lines and since I did not have a reference star for flux calibration, I rectified (flattened) the spectra.
Apart for the strength of the H alpha line which was saturated in the jpg image, the agreement looks good.Cheers
RobinAttachments:
Hi Mike,
The spectroscopy database is not designed to take spectrum images and though digitisation is straightforward using freely available software, the precise wavelength calibration of objective prism spectra is tricky due to the lack of a reference point and very non linear dispersion. It could still probably be achieved though. Do I remember correctly that you had a previous setup which allows some light from the star to bypass the prism, allowing an image of the star to be produced? This could be used as a reference point for wavelength calibration. If you are interested I could take a look and see what could be done. (The database does allow an image to accompany the digitised spectrum so the original spectrum image could be archived alongside the calibrated digitised version)
Cheers
RobinWith Chrome, I am logged out as soon as I close the tab. I do have an advert and 3rd party cookie’s blocker, though other forums eg Cloudy Nights, Stargazer’s lounge keep me logged in unless I specifically log out
Cheers
Robinmight catch out people who don’t stay logged in all the time, like me.
You can stay logged in ?? How do you do that ? (I have never been able to stay logged in, a source of annoyance)
Cheers
RobinA spectrum taken 20260825.852 showing clear P Cygni profiles at H alpha and H beta. The velocity in H alpha is ~1500km/s confirming its status as a Nova
https://britastro.org/specdb/data_graph.php?obs_id=21386Cheers
RobinThe spectrum has changed dramatically in just a day
The brightness also dropped by a magnitude (AAVSO light curve)
A new feature has appeared between H beta and H gamma. It looks very much like the ‘Bowen fluorescence’ feature seen in cataclysmic variables (plus some He II ?) as it is much broader than the other lines
Yes it is there in my spectrum from last night. (blueward of where HeII would be) The spectrum has changed dramatically in just a day
https://britastro.org/specdb/data_graph.php?obs_id=21380%2C21367&multi=yes&mix_flux=yesCheers
RobinAttachments:
A spectrum from last night. Just managed to get 15 min exposure at culmination (12 deg elevation) in twilight. Impressively broad lines. H alpha FWHM ~3300 km/s
https://britastro.org/specdb/data_graph.php?obs_id=21365Cheers
Robinspectroscopy from other BAA members
Not BAA members (AFAIK) but the 2SPOT team have posted (parts of) an echelle spectrum taken from Chile here
http://www.astrosurf.com/topic/184807-nova-sur-2026c/Cheers
RobinHi Grant,
I think to engage people interested in the science side of astronomy you have to be where the largest numbers who might be interested can be found which is in the astro forums and the profile of the BAA is very low there.
I spend a lot of time out there in various groups engaging with people interested in spectroscopy, promoting spectroscopy, showing examples and helping them. While most of it is in the science sections of general astro groups or special interest groups (If you look at what is going on in the Cloudy Nights Scientific Amateur Astronomy subforum for example, there is some interesting stuff going on there), I also drop in on the “pretty picture” imagers from time to time to give a science view of what is in their images, show them a spectrum, explain why light leaks in their filters is turning the red stars in their narrow band filtered images into planetary nebulae etc which generates quite a bit of interest. As part of that I also try to raise the profile of the BAA where I can, linking to the gallery, video talks, spectra in the BAA database, section content etc which at least brings them to the BAA website. Jeremy is on Stargazers Lounge and there are a couple of others but generally I don’t often see other BAA members.
Concerning AI, it can only find the good stuff if it is out there. In Cloudy Nights there is someone building an impressive “point an click” application which can take an image full of slitless spectra taken using a Star Analyser and identify objects in it, generate fully calibrated spectra and roughly classify them. He is using AI a lot and commented that most of the queries about using the Star Analyser lead back to stuff I put out there.
Much better result showing hydrogen emission lines (and a hint of Fe lines?)
That is interesting. Unlike the spectra in the ATel and your latest spectrum, my spectrum from 20260813.103 definitely shows no net emission except for the H alpha P Cygni. (I’ve double checked everything and there is no obvious issue with the result so it looks like it has gone from emission to absorption and back to emission in a few days.
Cheers
RobinA spectrum from this morning. (ALPY 600 ~12A resolution)
https://britastro.org/specdb/data_graph.php?obs_id=21286
Quite a change from the one posted in the ATel. Except for a narrow PCygni profiled H alpha, all other lines are in net absorption currently. It is also significantly red, (the one in the ATel had been rectified)Cheers
Robin
