[Big Ear Masthead]

The Ohio Sky Surveys
A Quick Review of the Data, 1965-1975

Legend

"survey"
the name given to the period of data collection, processing and publication. There were seven surveys, and a Supplement 2, each published in the Astrophysical Journal.

"decl"
the declination covered by the survey. Some surveys did two sets of declinations.

"RA"
the range of right ascension. Not all surveys were able to cover all 24 hours of right ascension.

"beam @ RA", "beam @ dec"
refer to beam size (the half-power beamwidth, which is the width of the main beam between the points at which the power has dropped to 1/2 of the maximum, measured in minutes of arc), which varied slightly with declination, and with an upgrade to the flat after Survey V.

"start d/m/y", "end d/m/y"
dates of data collection for each declination.

"# scans avr"
the number of scans averaged together to produce preprocessed data at each surveyed declination. The telescope was moved 20 minutes of declination at a time. Scans were at 0, 20 and 40 minutes of declination for each degree, at the then-current epoch.

"integration time"
period of time (in seconds) data was integrated or averaged over to collect a data point.

"RMS noise"
the level in Kelvins of average noise. Sources were considered "not detectable" when close to this level. (Don't confuse Kelvins with Janskys!)

"confusion"
the resolution level in Kelvins.

"contour interval"
the step value in Kelvins

"2650 data", "612 data"
the Ohio Survey also took data at 2650 MHz and 612 MHz for some surveys.

For All Surveys

  • bandwidth = 8MHz
  • scans 20' apart, except survey VI, decl +34 to +40 10' apart
  • results from multiple scans except survey VI, decl +20 to +30 single scans

For Some Surveys

supplement 2
taken from analog records in archives from 12/67-1/75 (?).

"6th/3rd" drift removal
each 2hr scan section fit with 6th order polynomial. average scan (2 or more) fit by 3rd order polynomial

"sd/10" drift removal
running standard deviation to remove sources, then integrate over 10 beamwidths (100'?) to obtain drift curve. subtract drift curve, average all scans compute and remove each point source response until "arbitrarily close to zero" then sum all point source responses

(V) underestimation in flux density in surveys II,III,IV
approx fix: increase fd of .16fu

(VI and earlier) map corrections
"this and previous surveys drawn on rectangular grid w/o correction for precession, aberration, nutation. use Source list for accurate position. each block was best fitted at corners for transformation to epoch 1950.0 coordinates."

View Survey Data in Non-Table Format

The Ohio Survey Data
SurveyIIIIIIIVVVIVII2
decl max 13837200634101
decl min 125310-16400-36-11
decl max 2 31 -1663-25
decl min 2 19 -3640-31
RA min (hr)80000005;21
RA max161624242424248;24
beam @ RA1010101010888
beam @ dec43~40~40~4042-50~40~40
start d/m/y2/3/6510/657/671/684/6911/709/7212/67
end d/m/y2/7/654/661/684/6910/699/727/731/75
start d/m/y 1/70
end d/m/y 10/70
# scans avr2-52+2+ 1-2
drift removal6th/3rd6th/3rd
sd/10
sd/10sd/10sd/10sd/10sd/10sd/10
integ time sec40 99.3
10
1010
rms noise K.02 .025.023 .023.023
confusion K.01
min source fu..37.16.16.16.18.18.18.25
contour int K.025.033.033 .033
contour int K .041.041.041
2650 data yesyes yesyes
612 data yes?yes?yes?yes?yes?

[][][]

HOME | FEEDBACK
Copyright © 1996-7 Big Ear Radio Observatory.
Originally designed by Point & Click Software, Inc.