Instrument configuration
(1) MERCATOR/MEROPE with RG filter, 2k*2k CCD (no windowing).
CCD area is 6.5 * 6.5 arcmin, N right, E down.
Telescope pointing rms ~ 2 arcsec (empirically).
Good tracking,
autoguiding not required if exposure time <~ 3 mins.
Acquisition parameters: no centring.
(2) NOT/ALFOSC
We require spectroscopic resolution R ~ 3.5 A to match SDSS (R = 2.8 A), and wavelength coverage of most of the visible window, so the useful grisms are:
No. Resn. Range Disp. Exposure times (sec) for S:N = 12
A A A/pixel R < 19 R < 19.5
#14 3.8 3275 - 6125 1.4 1500 2000
#8 3.5 5825 - 8350 1.3 1500 2500
(3) INT/IDS
Setup used 3+4/3/08:
R300V, central wavelength 5500 A. This delivers 2300 pixels of
unvignetted spectrum at 1.88 A/pixel, = 4320 A,
i.e. a range ~ 3500 - 7500 A.
The resolution is 4.1 A.
The CCD pixels are 13.5 mic, 0.4 arcsec. Use slow speed, no binning, window [850:1050,1:4200].
Ideally, use an order-sorting filter to block light below 3500 A, but it's not very important.
Best focus, 3/08, was 14.85.
There is severe fringing redward of 7000 A.
Observations required
(1) MERCATOR/MEROPE
200-sec integrations on all targets, the aim being to obtain
few-% precision relative photometry.
(2) NOT/ALFOSC
12 nights ALFOSC + IDS time, spread over Feb - Jun, corresponds to
~ 120 hours usable bright time, i.e. time to observe the top-ranked
~ 100 qsos. During each month, concentrate on the low-RA
objects, which may be difficult to catch in later months.
For quasars with z < 3, i.e. CIV emission blueward of 6200 A the red (grism #8) exposure is not required.
The exposure times (above, 1500 - 2500 sec)
are for S:N per resolution element ~ 12, which should
suffice to search for variations in absorber depth.
Most of the absorbers fall within the range covered by grism 14,
so we'll probably use this most of the time.
Acquisition overheads
~ 300 sec?
Observe at parallactic angle.
Calibrations: biases, W flats, arcs at start/end of night only, plus one observation of a standard star.
For R < 19, try exposure times of 1500 sec for each of gratings #14
and #8.
For 19 < R < 19.5, try 2000 and 2500 sec for gratings #14 and #8.
The goal is S:N of = 10 per resolution element (~ 3 pixels).
Try extracting a few spectra to see if the expected S:N is being
achieved. If not, integrate longer and sacrifice some of the
sample.
(3) INT/IDS
Aim for S:N per resolution element ~ 12. Probably, exposures ~ 1800 sec are needed. Take single exposures, don't split as 2 * 900 sec.
Observe at parallactic angle.
Calibrations: biases, W flats, arcs at start/end of night only, plus one observation of a standard star.
Observing reports
These notes supplement the automatic observing logs.
See the master sample list for a summary of which qsos have been observed with each telescope.
(1) MERCATOR/MEROPE
Support astronomer = Saskia, first night only. No telescope operator.
Setup: MEROPE / RG filter / EEV42-40 2k*2k CCD
Field 6.5' x 6.5', 0.19 "/pixel (N right, E down)
Tel pointing ~ 2" rms
Tracking: no autog needed if exposure <~ 3 mins
Acquired targets with 'nocentring' option
CCD linear to 50k
'Observed' below means S:N >~ 100.
Date Runs
---- ----
080117 139819 - 139924
18 139970 - 140000
19 140002 - 140111
20 140112 - 140207
20080117 (Chris, Sarah)
--------
Light cirrus for much of night.
Observed:
q11/1 3 24~ 29 35 36 40 41 44 52
q12/10 12 13 26 39 (twice) 41 52 65~ 66 70 104 109 126 162 166 331
q13/5 9 12 24 38 50 61 72 85 101 105 106 109 115~ 126 146 157~
q14/28 38 41 74 131 158 159 187 209 308 369 370
Notes:
q11/1, q12/166 look like galaxy
q12/41 has bright star few arcsec way, good for AO?
20080118 (Chris)
--------
Thick cloud most of night. Abandoned telescope at 05:00.
Autoguiding may not be working OK on the last 3 nights.
Observed:
q11/11 22
q12/22
20080119 (Francisco + Chris, Paul first half)
--------
Clear sky at start.
Observed:
q11/none
q12/2 6 15 16 52 53 73
q13/7~ 9 15 65 110 156 163 164 169
q14/23 31 34~ 35 37 42 63 67 68 74 81 84 170 219 239 240
310 322 346 367 368 371 430 450 455 457 462 463 491
538 540
Notes:
025 aborted
20080120 (Francisco)
--------
q11/5 19 20 38
q12/none
q13/136
q14/70 103 109 176 232 234 270 275 283 292
Notes:
No flats, very windy at start of night
125 wrong filter (VG)
(2) NOT/ALFOSC
Setup ----- ALFOSC / 1" slit / Grism 14 (no second-order blocking filter) / EEV with CCD in hi-gain mode, binned 2*1 (spatial * spec), window [900:1200,1:2048] Spatial scale 0.19 "/pixel, so 0.38" per binned pixel. Grism 14 -> 3275 - 6125 A, 1.4 A/pixel, R = 3.8 A. Spectrum blue -> red runs from top to bottom of CCD. 20080214-16 (Ignacio, support = Sami) ----------- Bad weather every night - no observations. 20080605 (Karl-Heinz, Flori, support = Amanda / Zita) -------- Clear, seeing 0.8 - 1.2" The usual electrical noise (probably 'salt-and-pepper'), manifested as curving bands on the CCD, but very low-level. Spectra are at x = 1050. ~ 18 qsos observed, S:N ~ 20 / resolution element.(3) INT/IDS
Dates: 3,4/3/08, 25-27/4/08, 5,10,11/6/08
Setup
-----
Setup on first night 3/3/08, assumed identical for the other 7 nights:
IDS235 / 1" slit / Al wide collimator / R300V grating / cenwave 5500 A
with
CCD EEV10 (13.5-mic pixels) in slow mode, no binning,
window = [850:1050,1:4200].
Best spec focus = 14.85
Spatial scale 0.4 "/pixel -> 80" slit on CCD.
Spec scale 139 A/mm -> 1.88 A/pixel -> 4300 A unvignetted.
For cenwave 5500 A, this -> 3350 - 7650 A (runs from top to bottom
of CCD)
No second-order filter used (at least on 10/6/08, I assume the same on
other nights).
Spec resolution: 1.05" slit -> 30 mic on CCD = 2.2 pixels = 4.1 A
(cf SDSS resolution 2.8 A)
Vignetting is quite sharp outside the range 870 < y < 3145.
There is severe fringing redward of ~ 7000 A.
There is a defect on the slit at x = 518.
Exposure times
--------------
Initially, 2 * 1000 sec, later 1 * 2000 sec to improve readout noise.
Summary of nights
-----------------
080303 crb/sb Cloudy most of night, seeing ~ 2"? 75% cloud at dawn.
Ignore the expoures with cenwave 6250 A
080304 crb/sb Clear most of night, seeing 1-2"
080425 fmm Come cirrus, cloudy later on, seeing 2-5"
080426 fmm Clear at start, cloudy later, seeing 2"
080427 fmm,fj Clear (some dust), seeing 2.2-2.5"
080605 crb/sb Clear, seeing 1.5"
080610 fj/crb Clear, seeing 0.7" at WHT DIMM
080611 fj Clear, seeing 0.7" at WHT DIMM
Notes on individual exposures (additional to those in the logs)
-----------------------------
609334 not properly guided
618691-2 high airmass, prob vignetted by dome
618704-5 rubbish (no guiding / twilight)
619166-8 problems with guiding?
Chris Benn
(crb@ing.iac.es)
Version: 2008 Nov 7