LOTUS: A low cost, ultraviolet spectrograph

I. A. Steele, J. M. Marchant, H. E. Jermak, R. M. Barnsley, S. D. Bates, N. R. Clay, A. Fitzsimmons, E. Jehin, G. Jones, C. J. Mottram, R. J. Smith, C. Snodgrass, M. de Val-Borro

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We describe the design, construction and commissioning of LOTUS; a simple, low-cost long-slit spectrograph for the Liverpool Telescope. The design is optimized for near-UV and visible wavelengths and uses all transmitting optics. It exploits the instrument focal plane field curvature to partially correct axial chromatic aberration. A stepped slit provides narrow (2.5x95 arcsec) and wide (5x25 arcsec) options that are optimized for spectral resolution and flux calibration respectively. On sky testing shows a wavelength range of 3200-6300 Angstroms with a peak system throughput (including detector quantum efficiency) of 15 per cent and wavelength dependant spectral resolution of R=225-430. By repeated observations of the symbiotic emission line star AG Peg we demonstrate the wavelength stability of the system is less than 2 Angstroms rms and is limited by the positioning of the object in the slit. The spectrograph is now in routine operation monitoring the activity of comet 67P/Churyumov-Gerasimenko during its current post-perihelion apparition.
Original languageEnglish
Pages (from-to)4268-4276
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date30 May 2016
Publication statusPublished - 21 Aug 2016

Bibliographical note

Accepted for publication in MNRAS. 10 pages. 14 figures


  • astro-ph.IM
  • astro-ph.EP


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