[Oct28] The choice of slit size, one method in work

About the slit size:

You know tht the slit width will impact the spectroscopy. And do you know what is the proper width you should choose?

In an observation that you need both high resolution and perfect normalization, you can do like this. Observed with an narrow slit with enough exposure time to get the spectrum with enough resolution, then with a quite short time exposure with a wide enough slit which contain all of the flux of the source to get the real flux level. The width slit spectrum is only useful to determine the normalization of the flux. Just shift the the high resolution spectrum and you will get the perfect spectrum with both high resolution and real flux level.
You can have a simulation here: http://terpconnect.umd.edu/~toh/models/AbsSlitWidth.html

About the normal study:
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Usually, you make a code or you make a simulation similar with others', but you do not know whether it is correct. Then try to compare the different results to make sure it is correct and also can help you to improve the results.