The UVEX spectroscope is a new instrument enabling amateur astronomers to study stars in near ultraviolet (for hot active stars) and infrared (for cooler stars and comets).
Designed by Christian Buil and developed by a team of French amateur astronomers, the spectroscope uses mirrors to avoid chromatic aberration which causes colour fringing in simple lenses. The optical design is based on the Czerny-Turner spectroscope shown below. A cylindrical lens is used to reduce the astigmatism inherent in the design.
The spectral range is 3200 to 8600 Angstroms or more, depending on the camera and telescope. Ozone in the Earth's upper atmosphere absorbs light strongly below 3200 Angstroms. The optimal resolution is R=750 (using a 300 lines/mm grating) but R=3600 can be achieved using a 1200 lines/mm grating.
Construction
The construction cost is around £300 for the optical parts (plus entrance slit) with most of the structural parts made by 3D printing. The optical parts are listed below. Plans, downloadable parts and tutorials are available on the project website (http://uvex-spectro.tech).
| Part | Description |
| Grating | ThorLabs GR25-305 (300 lines/mm) |
| Mirror M1 (fl 150mm) | ThorLabs CM254-074-G01 ? |
| Mirror M2 (fl 200mm) | ThorLabs CM254-100-G01 ? |
| Cylindrical lens | ThorLabs LJ1934L1-A |
Astronomical targets
The ultraviolet (UV) spectrum is important in the study of Be stars, which are hot stars (temperatures around 12,000 to 30,000 Kelvin) with prominent lines such as hydrogen in emission. The Hydrogen alpha line shows double-peaked emission at high resolution (R~10000) indicating a rotating disk of material around the star. According to a recent paper (Cochetti et al 2020), a significant number of Be stars also show a second Balmer discontinuity which can be investigated using the UVEX spectroscope.
Links
- UVEX project website (French/English)
- Christian Buil's design (French)
