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The NGC 2903 ALFA Survey

Az Drift, Declination Strip Log for Continuum Observations for Dec'04


Ideally, the beam maps would be made for a single, strong standard calibrator; however, because we are limited in this run to the same block of time as NGC 2903 and also because of its declination, there is not a single suitable source. Note that sources which transit close to the zenith cannot be observed in drift mode if the ZA gets too low, < ~2deg; for the beammaps, this limit is set by the southernmost strip in the map. Another problem arises because of the ALFA rotation angle limits; a source at +20 Decl. cannot be tracked all the way to the west in the same ALFA configuration, because the required optimal rotation angle would exceed the limit of +100 deg. These two reasons combine to eliminate 0850+20 as a calibrator. We were limited in this run to the time set aside for NGC2903 itself, and there is not another suitably strong continuum source close enough in Decl. The 0.5 Jy source 20' to the south is too far south and the field too messy (with extended NGC2903 within the map). The only solution that appeared to us was to use 2 different sources. The first 0805+21, has S(NVSS)=931 mJy. It is not a principal VLA calibrator, but appears fairly isolated. The second is 1021+21, from Lyle's suggestion, with S(NVSS)=1.7 Jy.

For these continuum observations, we use a 50 MHz bandwidth centered at 1405 MHz. The appropriate "saved state" is stored in /share/obs4/usr/a1963/a1963_beammaps.gui. To get enough coverage of the coma lobe, the scan duration is set to 240 sec; hence the "pseudo-RA" for these scans as indicated in the source catalog file, and the "Spectral Line Observer's Widget", is 2 minutes earlier than the continuum source position. The basic mode is a 240 sec drift followed by a 1 sec each CalON/CAlOFF sequence (CAL MODE = loopend).

In the table below, the Dec Offset is relative to the drift centered on the source's catalogued declination as follows:
0805+21 08:05:38.5 +21:06:51
1021+21 10:21:54.6 +21:59:31

# Dec Offset Dec J2000 Az#s Date/Schedule Comment
1 +000731 +211422, +220702 1-23 (04Dec23)  
         
2 +000538 +211229, +220509 1-23 (04Dec21)  
         
3 +000345 +211036, +220316 1-23(04Dec19)  
         
4 +000153 +210844, +2201241-23 (04Dec17)  
        
5 000000 +210651, +215931 1-23 04Dec06  
        
6 -000153 +210458, +215738 1-23 (04Dec18)  
        
7 -000345 +210306, +215546 1-23 (04Dec20)  
        
8 -000538 +210113, +215353 1-23 (04Dec22)  
        
9 -000731 +205921, +215200 1-23 (04Dec26)  

This page created for the NGC2903 group by Martha Haynes and maintained by Barbara Catinella

Last modified: Mon Dec 13 17:06:39 AST 2004 by mph