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Which guiders are you referring to?
AstroArt, PRISM, Audela have a specfic function optimised for guiding on a split image which can potentially guide better than PHD2. PHD2 normally just works though so if you are having problems getting PHD2 to work, I would not suggest moving to one of these at this stage.
What is the orientation of your slit? (I run mine along the Dec direction so any Dec errors due to backlash just move the star up and down the slit a bit)
Is your drift during guiding in both RA and Dec or just in Dec?If you have the green square and green cross the star has been detected ok and should be actively guiding. Also if the star moved correctly in RA and Dec during the training the mount is responding the the PHD commands.
I have seen this problem before I think. The RA (or Dec) guide corrections may have become inverted somehow (There may be a setting somewhere) so instead of correcting towards the right position it corrects in the opposite direction and the star continues to drift at an accelerating rate away from the guide position. It is connected with the meridian flip I believe. If you train and then guide on the same star does it work correctly ? Does it then not work if you move to a different star on the other side of the meridian ?
Watching how the star moves during the training is a good guide to whether the mount and settings are roughly ok. The star should move immediately in the RA direction in a series of obvious steps and then approximately back to the start position (there should be no backlash in RA if you make sure you slightly off balance the mount.) If there is backlash in Dec you will see PHD making several steps without any movement of the star (you will see a “removing backlash” message) I have lots of Dec backlash in my old eq6 but PHD still copes OK
Hello Jack,
I use PHD with my spectrographs.
(Note with PHD even when guiding properly, the star tends to move backwards and forwards across the slit because half the star is hidden when the star is slightly off the slit so it over corrects. There are guiders which work on the split image of the star on the slit but I have not used them)
You say the star wont guide on a star, the star wont stay on the slit.
Do you have the green square round the star with a green cross at the guide position?
Did the training work ok? First time you run (or if you hit shift when you start to guide) the cross is dottted yellow and the star is moved in X and Y to calibrate the guiding. (If the star does not move, there is a problem communicating with the mount and you will get an error message)
Does the star and green square stay near the guide position (centre of green cross) or does it continuously wander off?
If the star is staying around the right position but is moving around the guide position too much try guiding off the slit. Does it work ok then ?
Cheers
RobinHi Kevin,
Do you still have any PEP capability, particularly J,H bands ? I am looking for data on RW Cep to complement my spectroscopy as it returns from its deep fade
https://britastro.org/vss/VSSC195.pdf page 7Cheers
Robinwith the direct observation of exocomets I think I can now extend my section’s reach to other star systems.
Perhaps I can contribute the first indirect observation of exocomets to the section ? “polluted white dwarfs”
https://britastro.org/observations/observation.php?id=20210831_232116_04a034fbfd0ae832Cheers
RobinNote that alternatively if you use ISIS (Or Demetra) software with the calibration module it can find the wavelength calibration lines for you and do the calibration automatically
Hi John,
Is it this one ? (By a different Andy)
https://britastro.org/2017/guide-to-processing-spectra-using-the-bass-software
It is linked from the Spectroscopy resources page of the equipment and Techniques section here
https://britastro.org/section_information_/equipment-and-techniques-section-overview/spectroscopy
which used to be given in a sticky post at the head of this section of the forum but seems to have become unstuck !Cheers
RobinLars – I have sent you a PM
Off topic but how did you do that? I don’t see a PM facility on the new website (something I miss)
Thanks
RobinA continuation of the animation of the spectrum. Part 2 covers 2023-05-27 to 2023-06-13 and shows the transition from an almost featureless spectrum to one showing more typical broad P Cygni Balmer lines
https://britastro.org/observations/observation.php?id=20230614_144855_b767104d96087a30Cheers
RobinThe spectrum is now showing increasing features more typical of type II supernovae (Broad P Cygni Balmer lines)
Here is an example match in SNID to SN1980K 9 days past maximumCheers
RobinHere is a low resolution spectrum for the night 3/4 June. The continuum continues to cool and now matches a black body temperature of 9000K or an F0v star ((B-V) = 0.29.) The features are still weak with a very broad H alpha component with some structure evident at higher resolution. The higher Balmer lines are increasing in absorption blue shifted by ~8000 km/s
Attachments:
Attached is an example from the presentation of type Ia and type IIP spectra around or after maximum light.
Incidentally Koichi Itagaki also discovered both of these supernovae
Since type II supernovae are hydrogen-rich and type I are hydrogen-poor, would shooting through a hydrogen alpha filter be a quick-and-dirty way to distinguish them without spectroscopy?
Hydrogen present (in type II) or absent (in type Ia,b,c) in the spectrum would be a better description. The problem is other events also pretend to be type II supernovae like novae, dwarf novae, luminous blue variable supernova impostors etc. You need the detail of a spectrum to be sure of what you are looking at. The spectrum of supernovae also vary with time and with type II, H alpha emission does not really dominate the spectrum for a lot of it and when it does it is often a combination of emission and absorption (a P Cygni shape line). When typically measured a few days after discovery the type II spectrum can be almost devoid of features. This one was discovered early so did show some H alpha emission early on but even then the dominant feature was that is was very blue and currently it looks almost like an A type star but without hydrogen absorption lines, just a very small P Cygni H alpha line. See here the evolution of the spectrum over the first week.
https://britastro.org/observations/observation.php?id=20230528_140227_583fe05370c08912For a more general overview of using spectroscopy to classify supernovae I did a talk about it here
https://britastro.org/videos/using-low-resolution-spectroscopy-to-confirm-supernova-discoveries-2
In essence it is done by matching the spectrum to templates of various types of supernovae taken at different times
Attached is an example from the presentation of type Ia and type IIP spectra around or after maximum light. I think it would not be straightforward to distinguish them from just H alpha and broad band imagesCheers
RobinAttachments:
Just listened to an excellent episode of BBC World Service “Science in Action” almost entirely dedicated to SN 2023ixf
https://www.bbc.co.uk/sounds/play/w3ct4sc9
Astronomers, both amateur and professional talking enthusiastically about the discovery and what we know so far with lots of good science and even a live observing session on the radio!The evolving spectrum over the past week
https://britastro.org/observations/observation.php?id=20230528_140227_583fe05370c08912So B mag peaked in just 5 days from the explosion on the 18th. That’s pretty fast I think, even for a type II
It seems that the R and B are slowly swapping dominance!
Yes my spectrum from last night shows it cooling further to a black body temperature of ~12000K and a fit to an A3v star continuum with a B-V = +0.1
Attachments:
Very interesting thread.
Could I make useful spectra of the SN with my StarAnalyzer 100?
Yes it is certainly reachable with a Star Analyser for example
https://britastro.org/observations/observation.php?id=20230523_183229_5116a1a27f78a1ea
https://britastro.org/observations/observation.php?id=20230523_194606_cc526483f5e34422but the features seen earlier have greatly reduced and at the moment even with higher resolutions it is not showing very much except a slowly cooling blue continuum. Here is the evolution with my ALPY600
https://britastro.org/specdb/data_graph.php?obs_id=13786%2C13783%2C13778%2C13774&multi=yes&legend_pos=neCheers
Robin
