Aruna-1 Spectrometer Utilities

Capturing images of spectra using a tripod-mounted Aruna-1 spectrometer and a digital camera with manual focus and exposure settings opens up use of the instrument for recording and communicating your observations, and for performing quantitative analysis of the spectra. Some utility hardware and software are described below. These items are only examples of some available hardware and software. Other avaialable hardware and software may also be used for the same purpose.

Hardware Utilities

Digital Camera

A digital camera was used to record the images of spectra from the Aruna-1, displayed on these pages. We recommend using a digital camera with a manual focus ring, and manual exposure settings, in order to bring the spectrum into focus and to acquire sufficient light for capturing the image of the spectrum. The camera shown in the picture, a Canon EOS Rebel XSi, was typically used with ISO 800 or 1600 setting to obtain images of spectra.

Tripod Adapter

The Aruna-1 spectrometer may be attached to a standard camera tripod via its 1/2" diameter handgrip, and a standard optics post holder. This aids in taking pictures of spectra through the spectrometer. Standard tripods provides a 1/4-20 screw to attach a camera. Post holders which have a 1/4-20 thread on their base, and which accomodate 1/2" posts may be obtained from various optics companies. One example is the PH3 post holder from Thor Labs.

The hand grip on the spectrometer may need to be sanded to reduce the diameter by a very small amount in order to slip into the 1/2" post holder. Be sure to remove the grating card and cover the entrance slit if you need to sand the hand grip, so dust does not fall on these surfaces.

Software Utilities

After images of the spectra are recorded with the camera and transferred to a computer, the spectra may be processed using various software. We use the free GNU Image Manipulation Program, gimp, to clip the spectral region from the image, apply rotations, adjust brightness and contrast, and save the resulting image to a png image file.

Quantitative analysis of the spectra may be performed by further reducing the image data to a spectral line profile, using other image processing software. A simp program which allows a range of image rows from a png image file to be summed to give an intensity versus wavelength data set is SpectrumProfile.R, for use with the free computing environment, R.