[Difx-users] integration time

[Hagatiana Andrianomena]

Hi Cormac,

Please see attached the vex. I am interested in EF-YS-NK-HH-O8.

cheers,
Sam

On Mon, May 15, 2017 at 7:45 AM, Cormac Reynolds <cormac.reynolds at csiro.au>
wrote:

> hi Sam,
>
> just following up on Adam's point. The most common cause of a very high
> residual fringe rate (as yours appears to be) in an otherwise functioning
> array is an error in the station position(s). If you send the vex file you
> used, and the stations you are interested in, it should be straightforward
> to say if that is a likely cause or not.
>
> cheers,
> Cormac.
>
> On 13/05/17 19:57, Hagatiana Andrianomena wrote:
>
>> Hi Adam,
>>
>> Many thanks for your explanations.
>>
>> Cheers,
>> Sam
>>
>> On Sat, May 13, 2017 at 1:37 PM, Adam Deller <adeller at astro.swin.edu.au
>> <mailto:adeller at astro.swin.edu.au>> wrote:
>>
>>     Hi Sam,
>>
>>     Integration time will affect the maximum fringe rate you are
>>     sensitive to.  Shorter integrations = higher fringe rate before you
>>     lose signal due to decorrelation.  But normally this is not a
>>     limitation.  I would be fairly surprised if a 1 second integration
>>     time was a problem (unless there is an issue with the observing
>> setup).
>>
>>     Spectral resolution will affect the maximum residual delay you are
>>     sensitive too.  Finer spectral resolution = larger delay before you
>>     lose signal due to decorrelation.
>>
>>     These are not DiFX-specific things, but general to radio
>>     interferometers / correlators.  To know what values are reasonable,
>>     you need to know your instrument and what the expected residual
>>     fringe rate and delay are.
>>
>>     Cheers,
>>     Adam
>>
>>     On 12 May 2017 at 23:59, Hagatiana Andrianomena
>>     <handrianomena at ska.ac.za <mailto:handrianomena at ska.ac.za>> wrote:
>>
>>         Hi DiFX users,
>>
>>         I got a question regarding the integration time in the setup:
>>         SETUP default
>>         {
>>           tInt = 1.000000
>>           fftSpecRes = 0.12500000
>>           specRes = 0.12500000
>>           doPolar = True
>>           maxNSBetweenACAvg = 2000000
>>         }
>>
>>         I got this default setup by running oms2v2d using the .oms file
>>         from the experiment. When running the difx I got no fringe but
>>         from changing the tInt to
>>         0.08 and both fftSpecRes and specRes the result seems to suggest
>>         I got fringe (see plot attached).
>>
>>         I am not quite sure whether it is a naive question but I wonder
>>         if there is a simple rule of thumb to get the right values of
>>         those parameters in order to get fringe. I do not have much
>>         experience with DiFX I must say though.
>>
>>         Regards,
>>         Sam
>>
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>>
>>
>>
>>     --
>>     !=============================================================!
>>     Dr. Adam Deller
>>     ARC Future Fellow, Senior Lecturer
>>     Centre for Astrophysics & Supercomputing
>>     Swinburne University of Technology
>>     John St, Hawthorn VIC 3122 Australia
>>     phone: +61 3 9214 5307 <tel:+61%203%209214%205307>
>>     fax: +61 3 9214 8797 <tel:+61%203%209214%208797>
>>
>>     office days (usually): Mon-Thu
>>     !=============================================================!
>>
>>
>>
>>
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