Lesedi Spectrograph (name TBD)

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Lesedi Project Wiki

  • This wiki is for construction of a spectrograph on the 1-m Lesedi telescope in Sutherland. We anticipate future wikis for the user manual and for technical support.
  • The SAAO and LJMU (Liverpool John Moores University) are collaborating on the project.
  • The instrument is based on SPRAT (Spectrograph for Rapid Acquisition of Transients), which is currently operating robotically on the 2-m Liverpool Telescope on La Palma.

Project Team

Instrument PI: Iain Steele (LJMU)

Instrument Scientist: Helen Jermak (LJMU)

SPRAT Expert: Andrzej Piascik (LJMU)

Software Engineer: Chris Mottram (LJMU)

Local Co-PIs: Amanda Sickafoose & Hannah Worters

Local Electronics Engineer: Hitesh Gajjar

Local Mechanical Engineer:James O'Connor

Local Software Engineer: Carel van Gend


Points to consider (based on 27 Oct. Skype)

  • (1) Hannah to send Iain telescope optical prescription (done).
  • (2) Consideration of mounting, in terms of peripherals and control equipment — basically starting to think about packaging and how much needs to be mounted on the port vs. off to the sides, note that control of moving parts will be pneumatic (James/Egan).
  • (3) Question of which coating to buy for the Andor iDus camera -- new option has higher QE over wider range, but higher dark current (Amanda & Hannah)
  • (4) Question of whether we want two optimized wavelength settings, like SPRAT, or only one — the former aren’t being well used on SPRAT and the latter saves a moving part. although they say that they have plans to ensure that part is more reliable than the current version (Amanda & Hannah)
  • (5) Think about optimal slit size — 1.5” min, could be up to 2”, could also consider stepped slit — these are laser cut, and we could request more than one (Amanda & Hannah)
  • (6) Thinking about .fits header information for compatibility with data reduction pipeline, and how to integrate TCS with instrument to allow automated acquisition (Carel)


  • Point was raised that (rather than comount SHOC and this new spectrograph) we could use an iXon camera in the SPRAT system, add filter wheels, and effectively use it as SHOC when the slit, grating, and prisms are out of beam. The iXon has 1024 x 13-micron pixels as opposed to the iDus 1024 x 26-micron pixels. A test was performed at LT in the week of 15 Dec., in which the 85 mm f/1.8 camera lens was swapped out with a 50 mm Nikon f/1.4. The result from an arc was 7.70 Å/channel, central wavelength 6009.04 Å, range 4073.64 – 8018.33 Å. This range could be tweaked by tilting the camera slightly.

Some more details 50mmLensTest

Spreadsheet of pros/cons for proposed mounting options