How to process spectra recorded from the “DIY Spectrometer” using the “Spectrum Studio” software in either Microsoft Excel, RSPEC or VSPEC software.
The following is my summary and my own screenshots of the process using a solar spectrum I took using the DIY Spectrometer. I am indebted to Jeffrey L. Hopkins’ excellent book for teaching me about the process “Using commercial amateur astronomical spectrographs” and is the only resource that I know of that explains how to do this.
Processing the results from the DIY spectrometer in Excel, RSPEC, VSPEC:
Spectrum line profiles generated from the DIY spectrometer using its own software Spectrum Studio can be saved as a CSV file. Later we need to convert it in to a text file, once we have manipulated it in Micosoft Excel or Open Office or other similar spreadsheet programme.
Saving profiles from Spectrum Studio:
As shown in the screenshots above, Spectrum Studio automatically saves as CSV file which can then be directly loaded into Excel.
The CSV file produced includes a header with the scan date which uses the computers date and time, integration time which is the same as exposure time, and number of averages.
The following screenshot shows the Spectrum Studio CSV file as generated by Spectrum Studio opened in Microsoft Excel. I have highlighted the header:
Five columns of data will be found below this header.
Under the five columns are 2047 rows of data corresponding to the 2047 pixels on the linear CCD chip. Each row has an associated column for pixel number, wavelength in nanometres, sum, average, background. If the spectrum has been calibrated then the pixel number and wavelength will be the same.
The CSV file that is been saved above can be opened in Excel. Only two columns are needed for further analysis – the pixel number and the sum.
The following screenshot shows the Spectrum Studio CSV file opened in Excel with the Pixel Number and Sum columns highlighted – these are the two columns that need to be kept in order to open the file in RSPEC/VSPEC – other columns are deleted as is the header:
To create a line profile in Excel or Open Office or other similar spreadsheet programme, select these two columns and choose the desired graph from the options open to you in the spreadsheet software. The data files of multiple columns of ADU counts, Microsoft excel can be used to produce another column which is the sum of those counts for a given pixel position. That sum and pixel position can be used to create the line profile graph. The pixel number versus the wavelength can be determined and a new column created that shows the wavelength for each pixel position. The sum column and the new wavelength column can then be used to create a wavelength calibrated line profile graph. Such a graph would be very similar to the one that appears on the DIY spectrograph’s own spectrum software when you take spectrum.
Microsoft Excel helps allows you to manipulate the file so that it can be loaded in RSPEC/VSPEC but programmes such as RSPEC or VSPEC are easy to use if you want to process the spectrum in practice.
In order to open the text file from the DIY spectrograph spectrum in RSPEC or VSPEC, some changes need to be made to this text file. Open it in Microsoft Excel and then:
1. Delete the header data
2. Delete the column titles
3. Delete all columns except pixel number and sum
4. Save the resulting file as a text file. It does not matter from my own experience whether you save as Unicode text file or as tab-delimited – both with open in RSPEC/VPSEC.
5. Change the extension from .txt to .dat
The file can now be opened in RSPEC or VSPEC.
This file is not an image file any longer so it must be opened as a line profile .dat file.
Opening profile in RSPEC:
Once opened in RSPEC or VSPEC the profile can then be wavelength calibrated and further processed.