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I am trying to wavelength calibrate using the ALPY calibration module NeAr lamp and ISIS. I can get a good fit when I use the ATK314L unbinned but when I use 2x binned, the fit is very poor. (I have tried adjusting the pixel size either side of 12.9 but I cannot get a sensible result) Has anyone else tried this?

I suspect it is not finding the right lines. Is there any way to change or remove any of the lines used for the fit and verification to lines which might work better in 2x binned mode?

Thanks
Robin

By changing the pixel size in in 0.01A steps, I finally got it to work in 2x binned mode. (nominal 2xpixel size is 12.9um 12.81um works but 12.79 and 12.83um do not.)

I also found in unbinned mode I could get 2 different (but both still "good") fits with a residual RMS 0.22A at 6.45um pixel size and 0.14A at 6.40um. It is not immediately obvious which is the correct fit

Pixel size is clearly very critical to ensure the right lines are identified when using this method, particularly using such a rather high (4th order) fit

Cheers
Robin

Hi Robin,

I had the same issue but in unbinned mode (Atik 314L). Like you, I had to play with the 6.45 u value until I got one that worked (currently 6.37). I also found that I sometimes had to check the “Fixed Y value for sequence” box on the General tab. At the advice of Christian, I would normally leave this box unchecked, but I found that checking it was the only way I could eventually get the calibration to run..

Cheers,

Keith