Richard MASSEY
PhD student at IoA

Cosmic Shear Keck ESI fields
20 October 2001

I've found 7 potential cosmic shear fields during the night, so there is one overhead at any time you have a few minutes spare. I haven't given you airmass tables for each object, but merely listed the (sidereal) times while it is within 20^o of zenith. Please observe them during this window; and re-focus / MAlign before each shear run, to help keep the PSF down. Every field requires 3x200s exposures, one at each of these dither positions. We have found that it is easier and more accurate to tell these to the TO rather than to put them all explicitly into the object co-ordinate list.

The EllisR filter is long and thin; and well off-axis. The offset from it's centre to the centre of the CCD is ~74" E, but the TO should have an Ellis-R offset mode which includes this automatically. This also sets a PA of -98.70 which gets the long filter axis pointing East-West, consistently with our previous data. In the finding charts below, North is up and East is left. Use the CCD in default (fast readout, low gain) mode and please save the whole CCD area: it is possible to clip the unused region but this screws up my reduction pipeline.

I will also need photometric standards, bias frames and sky flats. Dome flats would be a huge bonus if you can get them done as well, please. Last time they were much better than the sky flats, perhaps because the sky was changing colour as they were taken. If you need to get in touch, e-mail me or call
+44 1223 766668 (office)
+44 1223 542649 (home)
+44 7440 648080 (mobile)

Thanks!

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• MAlign & re-focus
• Filter set: Clear_S/Ellis R/Clear_S
• Dithers: 3x200s seconds on each field
  (differences are from base posⁿ and in real arcseconds, not RA&Dec)

  [+0"      ,+0"     ]

  [+3.54",+3.54"]

  [+4.83",-1.29"] ...just an equilateral triangle with 5" sides

• Offset: Ellis-R
  PA -98.70, offset from CCD centre ~74' E
• CCD: dual-amplifier readout, fast readout mode, low gain
• Object co-ordinate list suitable for Keck starlist

A target list formatted to Keck specifications is available here.
A map of them on the sky, with our old fields, is available here.

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