Semester 2002B on the WFC - instructions for observers
What observations do we need ?
We have been allocated 1hr per night on all NL, WFC S/D and WFC Survey nights during semester 2002B (Aug2002-Jan2003). We require 2x320s exposure in each of the Sloan filters r' and i' on two fields centred near the bulge of M31. Hence 8 exposures in total are required. The centres of the fields are:
M31-microfld1 00 44 00.0 +41 34 00.0 J2000
M31-microfld2 00 43 10.0 +40 58 15.0 J2000
If due to your own filter requirements there is no room in the filter wheel for both the r' and i' filters, the r' filter is the more important one.
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How to take the observations
For your convenience and to ensure we get the data we need, a script is provided to automatically take the observations.
To automatically take the observations simply type the pathname of our script in the observing window on lpss13 (or whatever the observing Sparc is):
SYS> ~wfcm31/m31/obs_scripts/m31-microlensing
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What calibration frames are needed ?
We do not need specific calibration frames, but we may use some that you have taken for your own programmes or for the WFC Survey. If you have time to take flats, then twilight sky flats in r' and i' would be useful. Dome flats are not useful, so don't bother with these.
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Observing conditions
What observing conditions are required, and when should observations be taken ? We have been awarded dark, grey and bright time. Although M31 should preferably be observed at a time of night when the moon is below the horizon, bright time is still useful for us. Minimum seeing required is 2.0".
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What should I do with the data ?
After taking the observations, please run our script that will copy the M31 files to the ING ftp area, and mail various people on the the MEGA group to alert them that data has been taken and is available for ftp.
On lpss8 (logged in as intguest), simply type:
intguest@lpss8> /home/wfcm31/m31/copy_m31_data
NOTE: YOU MUST RUN THIS FROM THE intguest ACCOUNT ON LPSS8 DUE TO PERMISSIONS SET ON THE FTP DIRS.
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What if things go wrong ?
If the observing script bombs out due to some WFC hitch, then recovery procedures and the alternative manual method are suggested below (also see below for contact details for Jelte de Jong and Konrad Kuijken)
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Substantial amounts of time have been awarded over the past three years to the UK/AGAPE collaboration and the NL/US/UK MEGA project team to carry out a monitoring campaign of the bulge and disk regions of M31 to look for microlensing pixel events.
The MEGA team is continuing these observations during the 2002B semester at the INT. They will be carried out during WFC Survey nights, ING Service Nights, and NL scheduled observing nights. In compensation, PI's who have runs effected by the latter will have an extra night tagged on the end of their allocation, and similarly the WFC Survey will have an appropriate number of 'extra nights' allocated to make up for the time that it spends on the PATT/NL allocation of time for this monitoring project. The help of all the WFC Survey teams and all the scheduled observers is greatly appreciated by the collaborating members of the MEGA team.
This page is designed to provide basic information for observers who will be carrying out the observations for us. The observing will involve two exposures in two different filters (currently r' and i' - the Sloan DSS type filters) on two different field centres. Carrying out the observations is very straight forward for observers, as all they need to do is invoke a script in the WFC observing system. The script does the following:
- Checks that the instrument is at the correct rotator angle on the sky (180 degrees). If this is not the case, the script exits cleanly, and asks the observer to change the PA. The script can be restarted after the appropriate adjustment. Normally this should not be needed as 180 is the default observing position, but it is ESSENTIAL for the project that the fields are observed at this position. The sky PA can be changed to 180 from the SYS command window:
SYS>rotate sky 180
- Slews to the first field (after checking it is above the horizon!). The field centres are:
M31-microfld1 00 44 00.0 +41 34 00.0 J2000
M31-microfld2 00 43 10.0 +40 58 15.0 J2000
- Tells the autoguider of a star in an appropriate position to guide on. These coordinates have already been determined, and checked. If for some reason the script is failing, and one needs to do the observations manually, then the following commands can be issued:
SYS> guide on pixel 1772 521 (for M31-microfld1)
SYS> guide on pixel 700 148 (for M31-microfld2)
- Takes two 320s exposures in r' and 2x320s exposures in i'.
- Stops the autoguider, slews to the second field and picks up the appropriate guide star. Then again takes one 2x320s exposure in r' and 2x320s in i'.
On the observing Sparc (currently lpss13), simply type the following in the observing system window:
SYS> ~wfcm31/m31/obs_scripts/m31-microlensing
This takes approximately 1hr to run, including the overheads of acquisition and CCD read-outs. It is always preferable for us to have the dark observations taken, allthough data taken when the moon is up is still useful.
If there are technical problems during the running of the script and it needs to be aborted, you can do a ^C out of it. Depending on how far the script has got with the observations you may need to adjust it, or finish things by hand. In the case of the former (if you are familiar with c-shell scripting) - do NOT edit the versions in ~wfcsur/scripts - copy it to a dir under /home/intobs, edit it, make it executable and invoke it as a normal c-shell routine. Remember that this is what we need if you have to do it by hand:
2 exposure of 320s in filters r', and i' in BOTH fields M31-microfld1, and M31-microfld2 (coordinates above).
Please call the exposures M31-microfld1 and M31-microfld2 on the command line (or in GUI title field) so our ftp-copy scripts will recognise the files.
- For every night that M31 is indicated on the schedule the observations in the script must be carried out. This time sampling is crucial. So for example, 2hrs of observing on one night will not make up for 1hr on two consecutive nights.
- We can work with data which are ~3hrs over, as in typical 1" seeing at zenith this degrades to less than 1.5" when the INT is pointing ~3hrs over.
- The maximum seeing we can tolerate is 2.0 arcseconds. Do not bother attempting the observations if the seeing is greater than this.
- Photometric conditions are NOT required - we can cross calibrate from our already existing bank of good photometric data.
We do not request specific calibration frames are taken for this project, but we will use whatever complimentary frames happen to be taken by the observer that night (e.g. Landolt standards, flats and biases).
We have a script that you can invoke after you have taken the M31 observations. This script asks you for the full path name of the data dir, and then parses all the FITS files in this directory. It looks for the title keyword in the FITS header and picks out the files which have headers as entered by the script you invoked to take the observations. The script is self-explanatory, it copies these files (gzipping on the fly) to an ING ftp dir, and emails several people in the M31 MEGA group.
Please run this script every night you take M31 data - either at the end of the night, or preferably as soon as the M31 observing script has finished.
Run this script on lpss8 (the fastest machine we have available for the gzipping) by typing:
intguest@pss8> ~wfcm31/m31/copy_m31_data
Enter the full path name of the data dir at the prompt, leave to run (may take a while if there are many files in this dir, as it searches the FITS headers of all of them), and we will handle things from there.
Thanks for your help with the observing!
In case of queries or emergencies, contact Jelte de Jong or Konrad Kuijken:
Jelte de Jong
jdejong@astro.rug.nl
Phone: +31 50 3634081
Konrad Kuijken
kuijken@strw.leidenuniv.nl
Phone: +31 71 5275848