The Observing Programme in the North
This began in semester 2003B. Survey completion is likely by the end of 2007 or soon thereafter. The survey area is all galactic longitudes in the Northern Plane within the latitude range -5° < b < 5°, a total of 1800 square degrees. The INT Wide Field Camera (WFC) offers a pixel scale of 0.33" per pix, allowing on-sky structures above 1" in size to be resolved.
The observations constituting the survey are sequences of narrow-band Hα, Sloan r' and i' images obtained with the WFC. The Hα filter has a bandwidth of 95 Å and is centred at 6568 Å. For the accompanying broad-band filters we have preferred the Sloan filters
because of the more nearly rectangular shape of their pass-bands. The aim is to cover the survey area twice, observing once at each of a set of specified field centres that combine to cover the plane once, and then again at a second set of
offset positions. This strategy enhances our quality control and ensures
that strips of sky, otherwise falling in the gaps between CCDs, are not
left out altogether. The total number of field centres needed works out at 7635 x 2
The target faint-end limiting broadband magnitude is r'=20.
Hα filter exposure times have been set to give a roughly matched
narrow-band magnitude limit. The choices have been guided by the
desires both to match the limits of the AAO UKST H&alpha survey, and to allow
data-taking in bright time. In median seeing, saturation is likely to be at
around 13th magnitude. The telescope time needed to take data at each field
position (plus its offset) and move to the next field centre is approximately
10 minutes. The expected final seeing limit is likely to be 2 arcsec, although
this is under active review as the end of observing is approached. Standard
star observations are typically obtained every 2-3 hours to facilitate
photometric calibration of the survey data.
All imaging data obtained via this programme can be accessed from CASU by
any interested researchers working in UK, Spanish or Dutch centres.
From December 2007, source catalogues as well as images from observations obtained prior to January 2006 will be available via the Initial Data Release.
A report on the current status of the survey can be found here.
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