Fibre-feed tests at Izana in 2017 September

The new fibre-based spectrometer was updated from 2017 September 1 to 11. The detector electronic noise and atmospheric scintillation noise were both measured. The scintillation noise was found to be approximately 105 times higher than the electronic noise, and so the system is dominated by atmospheric noise. It is unlikely that the LCD-based system switching polarisation states at 5 Hz will be able to equal the performance of a typical Pockel’s-cell-based system switching at 100 Hz. An overall reduction in noise power by a factor of almost 5 times is required to match the performance of Fred in Sutherland. This difference is of the order difference in scintillation noise between 5 Hz switching and 100 Hz switching. Two fibre-feeds were trialled. A 30 mm focal length lens to replace the exiting 80 mm, and so focusing a smaller image of the Sun onto the end of the fibre, and a telescope arrangement coupling quasi-parallel light into the fibre. The shorter focal length lens resolves both the low- and high-frequency issues experienced since initial commissioning. The quasi-parallel telescope fibre-feed suffers some Doppler-imaging problems and also produces higher noise levels due to the lower light throughput. The primary cœlostat mirror was replaced, and resulted in an increase in counts for Mark-I by approximately 3%. The PMT HV-PSU was replaced, removing a temporary 2kV unit and reinstating the normal 3kV supply resulting in a further increase in counts for Mark-I by approximately 18%

Summary of autoguider wye cables

Wiring diagrams for the autoguider wye cables used on all five mounts are presented

Fibre-feed tests at Mount Wilson in 2016 September

A Skywatcher HEQ5-Pro motorised mount and Starlight Express Superstar CCD guide camera with OpenCV image processing were tested in use as a solar tracker. The best performance in RA and declination respectively was 0.00 ± 6.15 arcseconds and −1.32 ± 6.62 arcseconds. This compares favourably with data captured on the standard BiSON mount in Carnarvon where the RA precision was measured to be 0.158 ± 8.434 arcseconds and declination −0.066 ± 3.823 arcseconds. The spectrometer was temporarily modified to accept a fibre-feed from the new mount. A low-frequency "footprint" was present in the data residuals that was not resolved, but otherwise results were as expected and comparable to the standard network performance. Two WiFi access points were installed, providing coverage over the whole tower

Carnarvon health check

A brief look at the current condition of Mark V and Jabba in Carnarvon

Shutter repairs and updated fibre conversion at Carnarvon in 2019 February

Carnarvon was offline due to a shutter motor failure, and a computer failure. The shutter motor and reduction gearbox was replaced with the spare from the on-site shipping container. A new computer was installed. Further work was completed on the Jabba fibre conversion to resolve some ongoing issues and return the instrument performance and data quality to expected levels

Repairs to Jabba at Carnarvon in 2016 August

A major leak on the water-cooling loop inside the spectrometer caused serious damage to the printed circuit boards inside the rear connections box. The dome azimuth drive had problems with a damaged gearbox output shaft. Peltiers failed in two detectors. The linear polariser failed resulting in almost zero ratio. Repairs were completed sufficiently to get the site back online and operational, but significant work is still required. The water-cooling loop can not be reactivated without major repairs to the spectrometer chassis. The data now show a strong low-frequency footprint caused by the use of a lens from a pair of polarising sun-glasses as a substitute polarising filter. A CCD-based guider monitor was used to assess the guiding performance of the mount

Fibre-feed tests at Izana in 2017 May

A new fibre-based spectrometer was commissioned from 2017 May 8 to May 26. The system was initially commissioned using the light feed from the secondary cœlostat on the lower-level platform in the main observing room of the solar pyramid building. Limited operational time was achieved in this phase due to bad weather. At the end of the site visit the whole system was moved into the apex of the pyramid sharing light from the primary cœlostat with the Mark-I spectrometer, and remains running in this configuration. Data from the spectrometer suffers from poor low- and high-frequency noise that are thought to be caused by the size of the solar image formed on the end of the fibre. The guiding performance of the Skywatcher mount was tested when operating via a Raspberry Pi single-board computer, and results are consistent with earlier tests at Mount Wilson. No issues are expected with the use of the low-power system

The Hannibal temperature controllers

A temperature controller for Hannibal in Las Campanas

New computer in Mount Wilson

The PC in Mount Wilson had failed. A replacement was built in Birmingham and installed on this trip. A new UPS and mains controller were installed. The effect of the primary mirror position on beam alignment was investigated

Alignment of Klaus in Mount Wilson

The Pockels cell was emptied and refilled, all optics cleaned and aligned, a failing hard disk drive replaced, and the GPS repaired