The problem with this calibration is that relationship between pixels on x-axis and wavelength is not a simple y=Ax+B for slit-based spectrometers. I used a variation of Dr Elliott’s calibration Excel spreadsheet here which does assume that this relationship holds. I need to create a spreadsheet that allows generation of higher order equations. The DIY Spectrometer control panel will accept two higher orders if available, improving accuracy.
My calibration today used a linear equation.
Click on link below to download calibration files from today, including my calibration Excel spreadsheet for generating the equation and A & B from readings off the spectrum of a calibration light source:
Calibrating DIY Spectrometer 090818@1400
Screenshot from Spectrum Studio (below) (control software for DIY Spectrometer) – the spectrum is one I have taken of a Compact Fluorescent Light Bulb. I am attempting to identify the elements of a line on the spectrum using the line identification function in the software – yellow line.
Note that spectrum covers a narrower range than CCDSPEC as the defraction grating is 1800 lines/mm in the DIY Spectrometer rather than CCDSPEC’s 600 lines/mm.
Comparison spectrum taken approx. 10 days ago with CCDSPEC (below):
Sold by Science-Surplus, these are fiber-coupled spectrometers sold on ebay. They provide quite high resolution at very cheap price – the big question is how it is going to be attached to my telescope but that is a challenge for another day!
Description of instrument from Science-Surplus:
This is a reconditioned compact fiber-coupled CCD spectrometer. It is a crossed Czerny-Turner design originally manufactured by B&W Tek, Model BTC-110S. It is an OEM instrument formerly used in a medical device and is sold “as-is.” The spectrometer includes an 1800 l/mm grating and the CCD detector is not actively cooled. The spectrometer is not aligned. However, it is “pre-aligned” so that the unit measures the spectral range of about 500 nm to 700 nm with a resolution typically better than 2-3 nm, The grating can be rotated to measure wavelengths below 365 or up to 700 nm (in first order) with a 200 nm total range. An order-sorting filter is typically not included. The spectral resolution can be 1 nm when the alignment is optimized. Other gratings can be purchased for different spectral coverage. Aligning the spectrometer is not trivial.
The kit includes the spectrometer, a custom enclosure (shown in the photo), a fiber optic collection cable (SMA), 5 volts DC power supply, and a serial port communication (D9) communication cable. The kit also includes access to our proprietary Spectrum Studio ©2018 software to read out the spectra, calibrate the wavelength scale, record and/or average the data with or without dark subtraction.
- UV-NIR (coverage is typically 200 nm. Min/max wavelengths are 365 and 700 nm)
- 1 nm Spectral Resolution (optimized)
- 16 bit Digitizer
- RMS read noise <50 counts (typical)
- Sony ILX511 linear CCD detector array
- ~350 ms Readout Time
- 20 Hz analog spectral readout possible
- overall dimensions: 5.75 x 3.75 x 1.75 inches
- Spectrum Studio, ©2018 Science-Surplus available as a download
- Windows XP, Vista, 7, 8, and 10 compatible
- Integration time from 50 to 65535 ms
- Average 1 to 1,000,000,000 scans
- Single scan or continuous scanning
- Save and load spectra (csv file format)
- Dark signal subtraction
- User input coefficients for calibrating the wavelength scale
- Instructions for creating your own custom software interface
- Windows .NET framework 3.5 (in English)
- Serial Communication
- 9-pin Comm Port or USB to Serial adapter
- [Note added by Andrew Thornett = works well through USB 2.0 with USB-serial adapter on my Windows 10 Dell 5 5000 laptop]
What’s in the box
- Compact CCD Spectrometer
- SMA fiber optic patch cable, 0.5 m length
- 5V wallplug power supply
- 9-pin Serial Communication Cable