General Description

In order to optimize the discovery of supernovae, we have carefully selected ~25 Mosaic pointings distributed over the sky. The selection was complicated by the fact that we must observe the same fields for three months (Oct, Nov, & Dec) during only the first HALF of the scheduled nights (usually every other night of dark and grey time). The selection, and distribution, of fields was driven by this constraint to be within the RA range of ~23h to ~3h, and even this range pushes the limits at either end of the observing season.

Additional selection criteria included...

• fields must be between Dec = +01:00 and Dec = -25:00 to allow follow-up from Northern hemisphere telescopes
• must be able to observe each field set during allocated time each half night (i.e., field set must be DISTRIBUTED to allow observations of all fields)
• throughout search season (approximately Sep 15 - Dec 30), field must be at airmass X<1.7 at some time during night
• should minimize bright stars, with no stars m<8 and preferably few stars with m<10
• low galactic extinction
• low I-band cirrus
• out of the galactic plane
• maximize overlap with other surveys (SDSS, NDWFS, DLS, etc.)
• moon preferably not passing through the fields
• preferably out of the ecliptic plane

The selection analysis focused on the galactic extinction, survey overlap, and airmass as a function of time and month. For survey overlap, we concentrated on two large optical surveys, the Sloan Digital Sky Survey (SDSS) and the NOAO Deep Wide Field Survey (NDWFS). In particular, we tried to pick as many fields as possible in the SDSS equatorial strip, since in this area photometric redshifts (photo-z) for objects detected by SDSS are already publically available the SDSS SkyServer pages (click on Navigate).

Two Field Sets

The ESSENCE telescope schedule provides for observations every other night on the CTIO 4m telescope. In order to maximize the sky coverage, and therefore the number of SNe discovered and followed, we have selected TWO sets of fields which will be observed on alternate ESSENCE nights. This provides a field revisit cadence of every 4 nights, sufficient to produce high quality light curves under normal Oct-Nov conditions at CTIO (especially for intermediate and higher-z SNe where time dilation helps!).

Set Alpha Fields

Field Name	RA (J2000)	Dec (J2000)	Depth	RAW	Comments
waa6	23:25:01.12	-09:14:59.7
waa7	23:30:01.20	-09:44:55.9
waa8	23:27:27.02	-09:50:59.7
waa9	23:25:01.12	-09:50:59.7
wbb6	01:09:00.16	+00:10:43.3
wbb7	01:14:24.46	-00:20:17.1
wbb8	01:12:00.46	-00:20:17.1
wbb9	01:09:36.40	-00:25:16.7
wcc5	02:07:40.80	-04:20:00.0
wcc7	02:10:01.55	-04:55:00.0
wcc8	02:07:41.03	-04:55:00.0
wcc9	02:05:20.52	-04:55:00.0
wdd3	02:28:36.25	-07:48:17.3
wdd6	02:28:36.25	-08:24:17.3
wdd8	02:31:00.25	-09:00:17.3
wdd9	02:28:36.25	-09:00:17.3

Set Beta Fields

Field Name	RA (J2000)	Dec (J2000)	Depth	RAW	Comments
waa1	23:29:52.92	-08:38:59.7
waa2	23:27:27.02	-08:38:59.7
waa3	23:25:01.12	-08:38:59.7
waa5	23:27:27.02	-09:14:59.7
wbb1	01:14:24.46	00:51:42.9
wbb3	01:09:36.40	00:46:43.3
wbb4	01:14:24.46	00:15:42.9
wbb5	01:12:00.46	00:15:42.9
wcc1	02:10:00.90	-03:45:00.0
wcc2	02:07:40.60	-03:45:00.0
wcc3	02:05:20.30	-03:45:00.0
wcc4	02:10:01.20	-04:20:00.0
wdd4	02:34:30.35	-08:19:18.2
wdd7	02:33:24.25	-08:55:18.2
wdd2	02:31:00.25	-07:48:17.3
wdd5	02:31:00.25	-08:24:17.3

MOSOCS Files

To support more efficient observing and reduce the number of errors due to typos in coordinates or guide star selection, we use the mosocs task available for the MosaicII imager which controls not only the Mosaic imager but also the telescope (sending slew requests) and the guider (setting up on previously selected guide stars).

W fields 2004

• Group w-alpha file
• Group w-beta file

W fields 2002

Last updated: November 16, 2004 by C. Aguilera