Use the following filters: u(RGO), g'(SDSS), r'(SDSS), i'(SDSS), Z(RGO) and Ha for galactic plane sources.

Take a sequence of 5 bias exposures in the afternoon before each observing night.

These are necessary for a proper reduction, so make every effort to take them.

• Ideally, a set of 5 twilight flats per filter should be taken. If weather does not permit that, you can do with 3.
• There is an automated procedure that you should use which tells you what exposure time you need in twilight to get 20000 counts/pixel.
• Point the telescope to a Blank field (the telescope operator should have a list of those) and track. Offset the pointing positions by small amounts (10") diagonally, i.e., with both offsets in RA and DEC. Remember that offsets are absolute to the nominal position and not relative.
• You can alternatively point the telescope at some angle from the Sun (some say that there is an angle ~25º? where gradients in the flat field are minimal) and switch tracking off to take the flats.

Observe at least twice photometric standards of the Landolt list. The recommendation for the WFS is one of the following (see table):

sa92-335 00 55 00 00 44 13 J2000

sa95-330 03 54 31 00 29 05 J2000

sa98-670 06 52 12 -00 19 17 J2000

sa101-427 09 57 26 -00 17 16 J2000

sa104-334 12 42 21 -00 40 28 J2000

sa107-602 15 39 19 -00 15 29 J2000

sa110-361 18 42 45 00 08 04 J2000

sa113-163 21 42 35 00 16 46 J2000

In general, all observations should be done at airmass < 1.5, unless there are reasons for it (typically, no targets at smaller airmass).

Typically, exposure time should be:

High galactic latitude fields: u(1200s), g'(600s), r'(600s), i'(1200s), Z(1200s)

Galactic Plane fields: g'(600s), r'(600s), i'(1200s), Z(1200s), Ha (1200s)

The highest priority should always be i'. Make sure you take appropriate flats for this filter at the earliest opportunity.

If the seeing gets worst than 1.5", exposure times should be scaled according to

T_exp µ (seeing/1.5 arcsec)²

At moonlit, observe with the reddest filters (i? and Z) and narrow band Ha . Double the nominal exposure time to achieve a similar sensitivity.

The nominal WFC pointing position is at the centre of CCD #4. This does not give optimal coverage of the EPIC field of view, so nominal XMM-Newton pointing positions have to be shifted to:

RA_WFC = RA _XMM + D RA/cos(DEC _XMM)

Dec_WFC = Dec _XMM + D Dec

where   D RA/cos=+2.5arcmin and  D Dec=+2.0 arcmin

Make sure, before you leave the site, that you send to xray@ifca.unican.es the following material:

• A report on the observations
• The electronic logs (ask the Telescope Operator where are these physically stored).

A copy of the data has to be sent to the AXIS PI to the following address as soon as possible and no later than one week after completion of the observations. That should be in the form of 4Gb DAT tapes. Take into account that WFC observations can easily produce 5 Gb/night.

X. Barcons

Instituto de Física de Cantabria (CSIC-UC)

Facultad de Ciencias

E-39005 Santander, Spain

For anything not specified in these notes, or if doubts arise, consult the Wide Field Survey pages at

http://www.ast.cam.ac.uk/~wfcsur/internal

You can also try the following phone numbers:

X. Barcons: +34-942-201461

F.J. Carrera: +34-942-201340

Mobile phone: +34-639-770454