[daip] IBLED

Leonia Kogan lkogan at aoc.nrao.edu
Tue May 21 10:13:48 EDT 2002


Phil,

Before start looking at the problem I'd want to be sure that the problem is 
related with the huge size of your data.

I'd appreciate if you UVCOP a small portion of the data and check if the prolem 
disapear. If not then I can try to fix the bug using the small data set, 
that is more convinient. I have a problem with memory at my computer.

Thanks

Leonia

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Date: Tue, 21 May 2002 12:34:38 +0100 (BST)
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I am reducing a large VLBA dataset on SiO masers in Orion. I am using
31Dec01 under Linux. The datset consists of two IFs, 512 channels and
~770000 visibilities. After some calibration I have run AVSPC on the data
to produce one channel, keeping the two IFS. I fed this dataset to IBLED,
averaging for 10 seconds from the 2.097 correlator integration time.

I can display and edit IF1 with no problem. However, when I switch to IF2
within IBLED the amplitudes contain what looks like strong, time variable
interference on all baselines. This is not real. Plotting the IF2 data
with VPLOT shows no sign of this. Rerunning IBLED and selecting IF2 at
input reveals very clean looking data. The problem arises when switching
between IFs within IBLED. I have never seen this problem before. However,
I have never reduced data from such a large file before.

Claire Chandler could probably provide a similar file for testing IBLED
rather than trying to ship over my data.

- Phil

------------------------------------------------------------------------------
Philip Diamond                            | pdiamond at jb.man.ac.uk
Director, MERLIN & VLBI National Facility |
University of Manchester                  |
Jodrell Bank Observatory                  | (+44) (0)1477 572625 (office)
Macclesfield                              | (+44) (0)1477 571321 (switchboard)
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U.K.                                      | (+44) (0)7769 706872 (mobile)


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