We present the first sky maps from the BEAST ( Background Emission Anisotropy Scanning Telescope ) experiment .
BEAST consists of a 2.2 meter off axis Gregorian telescope fed by a cryogenic millimeter wavelength focal plane currently consisting of 6 Q band ( 40 GHz ) and 2 Ka band ( 30 GHz ) scalar feed horns feeding cryogenic HEMT amplifiers .
Data were collected from two balloon-borne flights in 2000 , followed by a lengthy ground observing campaign from the 3.8 Km altitude University of California White Mountain Research Station .
This paper reports the initial results from the ground based observations .
The instrument produced an annular map covering the sky from 33 \arcdeg \leq \delta \leq 42 \arcdeg .
The maps cover an area of 2470 square degrees with an effective resolution of 23 arcminutes FWHM at 40 GHz and 30 arcminutes at 30 GHz .
The map RMS ( smoothed to 30 arcminutes and excluding galactic foregrounds ) is 54 \pm 5 \mu K at 40 GHz .
Comparison with the instrument noise gives a cosmic signal RMS contribution of 28 \pm 3 \mu K. An estimate of the actual CMB sky signal requires taking into account the \ell space filter function of our experiment and analysis techniques , carried out in a companion paper ( O ’ Dwyer et al .
2003 ) .
In addition to the robust detection of CMB anisotropies , we find a strong correlation between small portions of our maps and features in recent H \alpha maps ( Finkbeiner 2003 ) .
In this work we describe the data set and analysis techniques leading to the maps , including data selection , filtering , pointing reconstruction , mapmaking algorithms and systematic effects .
A detailed description of the experiment appears in Childers et al .
( 2003 ) .