Design, construction, tuning of spectroscopes
Information and discussion about softwares (telescope remote, autoguiding, acquisition, spectral processing ...)
It looks like the approximate Planck curve correction for the temperature of the flat lamp has stopped working in ISIS v5.9.6. Here is the same spectrum (wavelength calibrated but not instrument response corrected) processed in v5.9.3 and v9.5.6. David Boyd is also seeing the same problem
Cheers
Robin
hd174567b_raw_ISIS_593_596.png (27.36 KiB) Viewed 7181 times
It is the standard reduction using the ALPY predefined wavelength calibration mode. See the attached screen shot of the general tab and the xml configuration and log files in the zip file. I think David Boyd was using the LISA using a file mode wavelength calibration. The two spectra were produced using 5.9.3 and 5.9.6 with identical setups. The ratio of the two result is a 2700K Planck curve. See the attached comparison.
Here is my experience of trying the new version of ISIS 5.9.6.
hd43378_20190512_888_D.Boyd.png (28.09 KiB) Viewed 7103 times
This plot shows the result of the first step of processing LISA raw spectrum images to produce a dark and flat corrected profile but without response correction produced by 5.9.3 (black) and by 5.9.6 (blue). I use a .lst file to wavelength calibrate.
The ISIS code was changed during the update 5.9.4: I deleted the correction by the Planck curve during this update for the automatic processing because problems appear (consequences of other modifications, it would be a little long to explain here). It is now necessary to carry out this correction manually if necessary.
I will publish in a short time my UVEX spectra processing procedure, which of course adapts to LISA / Alpy. We will have the opportunity to discuss this important subject ...!
Ok, For now, I prefer to use the flat lamp correction for my ALPY spectra as I think it makes fitting the continuum easier. if I enter a 1/planck 2750K curve in the instrument response box instead of leaving it blank when calculating the instrument response, ISIS v5.9.6 behaves the same as ISIS before 5.9.4.
Hi,
I also have seen the same result as David Boyd when comparing the results processing HD114330 using ISIS 5.9.6 vs ISIS 5.9.1. (5.9.1 is the version I have been using until 5.9.6.) I also use a line list with file mode. The first plot shows the difference when the two calibrated but not yet response corrected results are compared. Same result as David showed above. And the later two screen shots that show this same difference from a different view point. I had noticed from memory when I processed this data in ISIS 5.9.6 that the shape of the curve looked a little different from when just the night before I had used the same reference star. And when I ready Robin's note I thought to look more closely. Interestingly when applying the resultant different response curves from the two version’s to the target star AG Dra, the resultant 1D spectrum are virtually identical.
Can someone (Paolo?) explain in more detail the multiplication by the 2750K Planck curve?
I will continue to use ISIS 5.9.1 until I get a better understanding of how to use ISIS 5.9.6 using the new procedure that Christian is working on for us.
Thank you.
Woody
Attachments
HD114330 ISIS version comparison.PNG (23.92 KiB) Viewed 7038 times
ISIS 5.9.6 Profile tab.PNG (30.18 KiB) Viewed 7038 times
ISIS 5.9.1 Profile tab.PNG (33.18 KiB) Viewed 7038 times
Hi Woody, I obtained the 2750K Planck curve with Visual Spec (Radiometry -> Planck). Anyway you can find it in attachment.
Try to do arithmetic operations between wavelength calibrated spectra using the Planck profile.
Please note that the problem I have mentioned concerns only old spectra processed with software versions before 5.9.4 and processed again with new ISIS versions by loading the original XML file. This is my experience, can anybody confirm?
The key thing to note is that the instrument responses calculated by v5.9.3 and v5.9.4 onwards will be different. If you calculate the instrument response and then reduce spectra with it using the same ISIS version there is no problem. You cannot mix versions though. I think this is what you are seeing Paolo. (The XML file is using is the old instrument response)
