Observing notes for the January 1998 2dF run

Night-by-night updates | Observing summary | Reductions and data |

Night-by-night updates

23/01-24/01
Thin cloud at start of night, observed two fields at the end of the sgp strip, but finished at > 4h ZD as 40 minutes was lost due to a computer crash which was unrelated to 2dF itself. Started observing an ngp field after midnight through intermittent thick cloud. At around 2:30am the computers were taken down by a power surge which also disabled the telescope for the rest of the night. Configuration time is roughly 12s/move.
24/01-25/01
Rain/thick cloud all night. Will's redshift code is now running at the telescope with an iraf front-end.
25/01-26/01
Clear all night. Seeing started at 1.5" but deterioriated to ~2.5". The override attempt to obtain further astrometric checks was abandoned without interruption of observing. Observed 1 sgp fields and 3 ngp fields with good quality data. Redshifts obtained for all but the last two fields at close of play. The positioner passed 5000 successive moves without a hardware failure. The start-of-night field has the highest completeness yet obtained, partly due to a plate hole leaving no objects in the infamous SW corner of the plate. Redshifts have been obtained at the telescope for 5/6 fields, although these should be regarded as a first pass. Some halation appears to be in evidence on the engineering chip (number 2).
26/01-27/01
Clouds around at the start of the night. Configured two sgp fields during the afternoon (314 and 319). Started slightly late due to a minor software problem, and then observed first field through some patchy cloud. Started the second field, but closed due to cloud around midnight before making any real progress. Sky clear by the time the next field was configured. Average move time decreases with time during the run and is now down to 11.1s. 40 minutes exposure obtained on NGP218 before the clouds returned.
27/01-28/01
Clear skies at the start of the night meant that we were able to get onto the first field (SGP237) and be exposing before the end of twilight. An extra exposure was yaken on this field because guide stars from different Schmidt plates appeared to be in different frames. The second field would have started on schedule, but was late due to software problems (CCDs), and so was observed at large HA. After midnight the rest of the night was given over to astrometric checks to try and pin down the swave problem. This time will be amply reimbursed from director's time. Analysis of the first field of the night suggests the discovery of a lensed qso, but could be a problem with the object identifications at the edge of the chip.
28/01-29/01
The fibre -> spectrum conversions on ccd2 of plate 1 were indeed found to have a mis-identification for the first retractor such that 10->5, and 5--9 all increment. Observations started in good time, and we were able to get three exposures on the second field before crossing the 4h boundary. Seeing deteriorated rapidly after midnight, and 45 minutes on sky was lost from NGP220 due to a CCD software error. The same error occured at the end of our time on this field, precluding any observations of a fourth field before twilight. Seeing has been apalling.
29/01-30/01
Last night: weather looks good at the start of the night, and we are aiming to re-observe sgp241 (from the first night) and another sgp field (318). This should give us a long strip (232--241) along the border of the qso survey and some fields above and below this area (313,314,318,319 and 166) which may allow me to extract a subset of the data that is as complete as it will get. Two fields observed without incident, one fibre needed to be disabled as it was in danger of failing (retractor), and about 10 minutes were lost due to a z-drive hardware error. One guide fibre on plate0 disappeared completely on ngp222, and the halation on ccd #2 has been particularly evident tonight, but the conditions have been fantastic. -We seriously considered observing one of the deep fields, but this was ruled out by halation.

Night-by-night updates | Observing summary | Reductions and data

Observing summary

The following summary gives the civil date of observation, field name, total exposure time (#exposures used for combined reduced image/#exposures taken x individual exposure time), nominal numbers of galaxies and QSO candidates in the field, the redshift yield for the galaxies (the fraction with Q=3,4 redshifts from WJSs code), the median difference between the photometric and spectroscopic magnitudes and an indication of conditions. All reduced data is available on the WWW (see below). 
Date    Field  Exposure  #gal #QSO Yield  Conditions

980123  SGP236 3/3x20min  244   97  75%   thin cloud
980123  SGP241 3/3x20min  308   36  53%   thick cloud, repeated on jan29
980125  SGP313 3/3x20min  234  104  97%   clear, 1.5" 
980125  NGP216 3/3x20min  291   75  88%   clear, 2-2.5"
980125  NGP231 3/3x20min  283   60  94%   clear, 2.5-3"
980125  NGP240 4/4x20min  324   42  94%   clear, 2.5-3""
980126  SGP314 3/15+20+12 253  101  88%   intermittent clouds 1.5-2"
980126  NGP218 2/2x20min  283   78  85%   closed after 2 frames
980127	SGP237 4/4x20min  253	82  92%   clear 0.9" 
980127  SGP166 3/3x20min  326    0  95%   clear, but started 4h over
980128  SGP238 3/3x20min  265   73  92%   clear, 1.5-2"
980128  SGP319 5/5x20min  282   88  93%   clear, 2"->4"
980128  NGP220 5/5x20min  291   69  95%   ended 3h from configuration time!!
980129	SGP318 3/3x20min  240   93  97%   clear, 1"
980129	SGP241 4/4x20min  308   36  90%   halation on chip 2, repeat from jan25.
980129  NGP222 4/4x20min  313   56  92%      1.4"-1.0"
980129	NGP239 3/2x20+1x30 292  53  92%   clear.

Night-by-night updates | Observing summary | Reductions and data |

Reductions and Redshifts

Reduced data: All the reduced data is available over the WWW from Here. The output .lis file from CONFIGURE is available and reduced data files are available as FITS files. These have been written from IRAF after patching the absorbtion bands and sky residuals/bad column, but should have correct object names in the headers, as inserted by GBD. Preliminary redshifts for these fields are also available *.zs. There are also plots *_swave.ps of the swave distortion for each field shown in terms of delta zero-point versus position inthe field. These are generated from a file *.flux.out which is also available, and has the following format: 

Spectrum Pivot Name RA DEC Mag Fibre_mag
It appears there was a minor problem with identifying the tramline for the first spectrum on chip 2 of plate 1, so there may be erroneous identifications in the first few spectra on these fields. For SGP237 we reduced the first two and last two frames separately (these are called a & b) as well as the co-added frame (c). BEWARE of mis-identifications of a pair of residual sky lines at 7600 Angstroms as H-alpha/NII at z~0.158 -- I think this is going to be a problem for some of these data.

Night-by-night updates | Observing summary | Reductions and data |

Gavin Dalton, gbd@astro.ox.ac.uk, Tue, Jan27