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We seem to employ both side of the argument here. The call for a spectroscopy section was turned down on the ground it was a technique and as it was mainly stars that were studied VSS was the right home. Now it seems that as Exoplants are mainly studied via photometery VSS should be its home.
I think the judgement should be on demand and potential contribution. Just how much overhead does a new section bring in the age of the internet?
Regards Andrew
Have a look at Christian Buil’s site he has evaluated several CMOS cameras for spectroscopy. Cooled CMOS should certainly be ok for guiding. Even NASA is going to fly a CMOS camera on its Parker Solar Probe mission.
Regards Andrew
Hi Jack, I have not done this with a Lhires III but I did try it with a LIAS. I used a 1:1 transfer lens(two doublets) to project the exit beam from a 50 micron fibre on to the entrance of the LISA with the slit removed. It worked fine but you get a 50 micron slit.
I had an F5.4 telescope which matched the F5 LISA even if the fibre reduced the focal ratio to about F4.5
This will be the issue with the Lhires III. It is designed for F10 so if you use a 50 micron fibre you will have a large “slit”
If you feed it at F10 you will get an F5-6 exit beam and so light loss. You could match the F ratios using transfer lenses but this will increase the size of the “slit” or vice versa. You could retain the slit but then you will get more light loss.
Hope this helps.
Regards Andrew
Hi Jack – forgot to say at the telescope end I use a Shelyak fibre injection unit. I think this is the most difficult bit to make with fibre fed spectrographs and well beyond my diy capabilities.
Regards Andrew
It might be worth pointing out that the H alpha line is made up of 7 components with two being significantly stronger than the others. The splitting is small withthe largest spin orbit coupling split in the 2p level (J = 3/2 ,1/2)
The theory of the spectrum of the Hydrogen atom traces the development of the quantum theory of light and matter. From the Bohr model where all the lines are degenerate in the prime quantum number (as the are in the Schrodinger model) through the development of Sommerfeld and Schrodinger to the relativistic theory of Dirac, Darwin, Lamb and on to QED for which Shin’ichirō Tomonaga, Julian Schwinger and Richard Feynman got the Nobel prize building on the work of many others, where they are all split apart.
If you go on the NIST spectral data base and look at the relevant lines it shows you the transitions involved.
As above the splitting is due to the spin orbit coupling of the magnetic moments.
Regards Andrew
There are a vast number of Fe II lines ( https://arxiv.org/pdf/1210.4773.pdf ) and in it’s other ionisation states so Fe is strongly influenced by radiation pressure compared to C, N or O which have fewer lines.
Regards Andrew
Tony I will follow your work and results with interest. Thanks for the detailed reply.
However there is no way I shall be hitting my spectrograph with a lump hammer!
Regards Andrew
3D printing seems about to revolutionise DIY astronomy. I look forward to seeing your work in July.
I do wonder how stable the parts will be compared to say aluminium alloy?
Regards Andrew
It is the spectrum you need to focus not the Star. So if you use the mask on the Star you will need to offset for the spectrum.
Regards Andrew
David look at Robin Leadbeater’s site as he designed the Star Analyser! Google Three Hills Observatory.
Regards Andrew
Hi Andy looking at 12 x 10 min Darks taken over two hours the mean value was 2664 +/- 1 ADU after hot pixel removal. If there were any drift in the Offset/Bias I would have expected a bigger variation and or trend.
I have observed that if you take a sequence of bias frames the temperature of the camera shifts slightly. In order to counter this I add a delay between taking Bias frames of 10s to let the camera re-stabilise. It may have no impact on the but I did not want to take any chances.
Regards Andrew
Hi Andy , camera as title. I have not looked for drift but will do so. It is run at a constant temperature in an enclosure held at a constant temperature so I would hope not! However, I will run some tests and report back.
Regards Andrew
Hi Kate, without more detail on your system I would go with one or more of the following
Poor seeing
Poor guiding with the star not staying on the slit
wrong target
Regards Andrew
I managed to do a similar thing with The Sky X with Nomad data base (1.1 billion stars), a Lisa spectrograph and my F5.4 300mm Newtonian. I think APT uses the UCA3 which may not have enough star for reliably plate solving the small field available. You can also have problems if a bright star is in the field as with a long enough expose to get enough stars to reliable solve the bright star can swamp the field.
Certainly worth a try.
Regards Andrew
