The Observations of LAMOST Jianrong Shi NAOC 1/7 2014

The Observation of LAMOST Jianrong Shi (NAOC)

Overview  The structure of LAMOST  The observation preparation  How to select the plate  The results from one year Pilot and two year standard surveys

Structure of LAMOST MB mirror 6.67 m×6.05m 4000 Fiber Positioni ng 4000 Fibers MA mirror 5.72m×4.4m 16 Spectrograph s 32 CCDs

Characteristics of LAMOST  A horizontal meridian reflecting Schmidt telescope with an active correcting plate  large field of view (5 deg) + large aperture (4m) Active optics on thin-mirror & segmented mirrors  4000 optical fibers on focal surface Parallel controllable fiber positioning

The observation preparation Focus the MB ( Shack-Hartman MA) ~5mintues Focus the MA and four guiding stars (center star V < 8 mag. ) ~25mintues Moving the fibers to the accurate positions (9mintues) (Which can be done during the focus)

MB 6.67m×6.05m Focal length 20m 37sub-mirrors

8 Segmented Active optics for 37 sub-mirrors of MB

MA 5.72 m×4.4m (24 sub-mirrors)

10 Segmented and thin mirror active optics for 24 sub-mirrors of MA

fiber positioning units (1.75m) Guiding CCDs S-H sensor for MA

4000 fiber positioning units

The site conditions The statistics of the number of hours of BATC observations per night from to The dashed line shows the theoretical available time.

Sky brightness The sky brightness in V band obtained from BATC Polaris monitor data, as a function of time from 1995 to 2011.

Telescope Seeing: 3-5 arcsec (dome + site)  Site seeing: < 2 arcsec ; Fiber size: 3.3 arcsec  has a field of view as large as 20 square degrees, the effective aperture varies from 3.6 to 4.9 meters in diameter (depending on the pointing). Enables it to take 4000 spectra in a single exposure at resolution R = Declination -10 o 60 o 90 o Effective aperture4.9m4.2m3.6m Field of view5 degree3 degree

Seeing Comparing the seeing from guide star and DIMM during Pilot Survey (Oct. 24, Match 30, 2012 )

Throughpot (Oct )

Signal to Noise Ratio

Throughpot (Oct )

Throughpot (Oct )

How to select the Plate Observational conditions: (240m) weather, Moon phase, left time and seeing etc. VB(9.0<r<14.0) 3*10m B (14.0<r<16.3) 3*20m – 3*25m M(16.3<r<17.8) 3*30m F(17.8<r<18.5) 3*30m readout ~ 8m Wish to observe two B plates and more VB plates

the image

The results from pilot survey Spectra with S/N>10 （ g or i band ） spectra plate success ratio pilot: 597, % First year: 1,191, % Second year:1,207, % success ratio: the ratio of the Spectra with S/N>10 to all the selected targets Observed time: 914h, 1278h and 1356h

The reason for the less plates during the second year Increase the time for foucs MB 、 B plate from minutes, added one lamp observation and more M plates observed LSS-GAC DR1 B ： 76 M ： 30 F ： 4 DR2 B ： 75 M ： 44 The instrumental fail rate (The ratio of the lost time due to the instrumental problem to the observation time ) Pilot: 12.5% first ： 5.3% second ： 4.4%

Thank You ！