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Someone has just posted a “Seestar brightness” measurement of T CrB on Cloudy Nights
https://www.cloudynights.com/forums/topic/932002-blaze-star-t-coronae-borealis-starting-to-blow/page/16/#findComment-14867872
even allowing for the rather wide uncertainty of +-0.2 quoted (much larger than the stochastic uncertainty based on the claimed SNR of 58) the 9.2 magnitude is significantly brighter than the current V,CV,TG from the AAVSO data which is running around 10Cheers
RobinI see on the forums it guides down to sub pixel level and is more stable than PHD2.
No more jitterbugs!What program is that Jack?
EDIT Sorry, Astroart. It is in the title! Ken Harrison got this split image guiding feature added to AstroArt many years back but it does not run with my camera so check for compatibility. (I think there is a free trial version ?)
PHD works well on field stars but guiding on the slit works best if you have a program specifically designed to cope with the “hamburger” star image with the slit running down the middle. Programs like PHD designed for normal star images tend to hunt back and forth as they alternately lock onto one half or the other of the split star image. With PHD, I found playing with the exposure can help, for example deliberately saturating the image but the best solution is a program designed to run on the split image. CCD Ciel can do this and is highly regarded among many spectroscopists as it can can handle the whole process up to and including fully automatic acquisition of spectra. AstroArt I believe also has the capability to guide on split star images. I’ve not tried them though as they are not compatible with my ancient guide camera.
Cheers
RobinIf the results are used in publications what are you going to use as a reference to the method? It would be helpful if ZWO were to write up exactly what they are doing and submit it for peer review. Without that it is just reverse engineering and guesswork.
Cheers
RobinSymbiotic CV QW Sge last night (Halpha/He6678 R~5000)
https://britastro.org/specdb/data_graph.php?obs_id=21595
Be Star HD350559 is still in absorption
https://britastro.org/specdb/data_graph.php?obs_id=21594Cheers
RobinHi Connor,
Here is a series of animations showing the spectroscopic evolution of a typical type II supernova SN 2023ixf over a period of a year
https://britastro.org/observations/index.php?page=1&page_size=40&sort_order=0&library=1&folder=163&obj1Type=0
Click on each one to see the details
I also summarised them in an article for the Variable Star Section Circular here
https://britastro.org/vss/VSSC199.pdfI am currently following the evolution of SN 2026sqf very unusual type Ia-CSM. Here are the spectra I have so far
https://britastro.org/specdb/data_graph.php?obs_id=21462%2C21370%2C21485%2C21269%2C21261%2C21235%2C21233%2C21231%2C21207%2C21202&spec_id=0&obs_observer_id=none&multi=yes&mix_flux=no&r_c=0&f_c=0&o_comment=&std_spectra_id=None&legend_pos=neCheers
RobinA quick spectrum last night between breaks in the cloud.
https://britastro.org/specdb/data_graph.php?obs_id=21438
Noisy but clearly a type Ia with a good match to several templates using SNID-SAGE at ~ one week pre maximum. (example attached).
The 6355A Si II absorption is at ~6135A giving an explosion velocity of ~ 9500km/s + 900km/s galaxy redshift = ~10500km/s significantly lower than ~13000km/s two nights earlier from spectra in TNSCheers
RobinJust 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
Robin
