One of the handicaps in astronomical spectroscopy, is in my opinion, the elevated costs of the equipment. Although we have now several options and lower prices, it still is a problem for those who want to give a step into spectroscopy but do not want to spend that price, just to try.
That was my motivation to sart building a classic spectroscope. I wanted to have an equipment, able to record decent spectra at a low/moderate cost.
I started by reading the excellent work of Christian Buil:
http://www.astrosurf.com/buil/us/stage/calcul/design_us.htm
His website is plenty of details, information, projects, etc. I really recommend visiting it.
My requirements for the DIY spectroscope were; feeding the spectroscope with an optic fiber. The telescope would have a fiber feeding head, through which would send the light to the spectroscope. This would reduce significantly the weight of the system, avoiding flexion/bending of the spectroscope depending on the position of the telescope. The spectrospe would be laying on a table. Not all are advantages, placing the focused beam from the telescope into the optic fiber is a big challenge, but I thought I would solve this later.
For this project I tried to use most of the materials I had and buy parts only if that was strictly necessary. I am detailing as follows, the list of materials I used for this project:
– 1 x Optical bench rails (NO mandatory).
– 1 x Low-consumption bulblight (IKEA).
– 2 x Piece of PVC tube (diameter:50mm x length:60mm)
– 1 x PVC tube reduction from 50mm to 32mm
– 1 x optic fiber with FC connector (length of 3m).
– 2 x male/male FC connector.
– 1 x 28mm photo lens f2,8 (collimator).
– 1 x Diffraction grating of 1800 l/mm “blazed” at 500nm.
– 1 x DSLR (Canon 500D) with 18-55mm lens.
– different types of clamps.
Following Christian Buil’s layout:
I started building my classic spectroscope:
In order to test the spectroscope, I place the low consumption bulblight into the PVC tube and placed on FC connector into the PVC tube reduction as shown in the following image:
This was the final complete assembly:
It was a bit difficult to properly align the ‘pin’ light source with the diffraction grating and the camera and once done, I realized different parts of the spectrum (different wavelengths) required different focusing.
In order to record the complete spectrum, I had to record 4 different parts of the spectrum and assemble a mosaic. This was the final result:
I am pretty satisfied with the results, I did not expect to get a spectrum like this. On the other hand I expected some aberrations to occur due to the optic fiber material. The optic fiber I used was made of polymer and i was not sure it would absorpt in the NIR (near-infrared) or NUV (near-ultraviolet), but I did not happen!
The next step is building an optic fiber feeding head to be placed at the telescope focuser.
Let's Science! 