November 30, 2016 at 4:55 pm #1442
I received a question from a coworker who is currently analyzing GMOS data and is at the point of determining the wavelength solution. She is not using the IRAF pipeline because our data are a bit unusual (high-precision timeseries in ROI format) and so is having to do the wavelength calibration by hand just using IRAF’s Identify task and the known line locations.
There are plots showing 1D arc spectra as a function of wavelength that users can use to identify lines in their arcs:
However, it appears that these are not matching well with her data – many of the lines are in similar places but not all, and the strengths are different. Does anyone know if there are more up-to-date plots or line lists that can be used if a user wants to do a manual wavelength calibration?
Thanks!November 30, 2016 at 8:20 pm #1443
You should first try flipping the X axis, and making sure that you still can’t get a match. When you open a GMOS fits exposure, you usually have the longer wavelengths on the left side of the image, which means that you need to flip the X axis to visually recognize a match to the reference CuAr images.November 30, 2016 at 8:24 pm #1444
Thanks for the quick reply! Sorry I should have mentioned – we did already flip the x-axis, so I know that isn’t the problem. The spectrum in the plots is similar to the data but not quite right. Sorry I can’t post an example – I was asking on behalf of someone else and I don’t have their data. I’ll get in touch with her and try to post an example, or see if she can post it.
In my case, I have data taken in 2012 which match well but her data was taken this year, so I can only assume that there may have been some subtle changes since then.December 15, 2016 at 4:27 pm #1455
Hi! Hope this is not off-topic but has anyone an atlas/plots of Cu/Ar identified lines done for an R150 Gemini-LS grating, so I can do the wavelength calibration?December 16, 2016 at 1:29 am #1458
You can have a look here for a spectrum with the B600 grating. I hope this helps you.
http://www.gemini.edu/sciops/instruments/gmos/calibration/example-cal-data/cuar-spectraDecember 19, 2016 at 5:34 pm #1459
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