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[vsnet-campaign 27] (fwd) Re: XTE J1118+480 ASCA-VSNET campaign



(fwd) Re: [vsnet-campaign 25] Re: XTE J1118+480 ASCA-VSNET campaign

   Forwarded because of the general (and urgent!) interest:

From: Giovanni.Sostero@elettra.trieste.it
Date: Thu, 11 May 2000 11:37:41 +0200

Dear Taichi,
it's nice for us to work with VSNet again!

About XTE J1118+480: it would be great for us to collect data with
sampling time better than 5 sec, but unfortunately the problem is that
with stars at V=13 or fainter, we are approaching the noise background
limit of our electronics. The photometer we are currently operating, is
based on an old 1P21 photomultiplier tube and electronics, that is very
"noisy".

For this reason I consider more safe to use an integrating time of 10
sec. According our experience, this is the only way to reach an accuracy
of the order of 0.05magn for such "faint" objects. Otherwise the risk is
to measure electronic background noise and not flickering.

Anyway, at the beginning of the night, we will try some 2 to 5 sec
acquisitions with the photometer; if the signal/noise ratio will be
acceptable, will will get it.

Unfortunately now the weather over north-east Italy is hazy and humid...

Regards,
        -Giovanni-

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