gpcal

Got a calibration problem? Discuss it here.

Moderator: Mark.Wieringa

Post Reply
julie
Posts: 12
Joined: Tue Mar 22, 2011 2:53 pm

gpcal

Post by julie »

Hi,

I am running gpcal on 1934-638 and my secondary calibrator 0400-319. I have 15 minutes of observations on 1934-638 (long story) and more on my secondary calibrator. The miriad user guide suggests using an interval of 0.1 minutes. Since I have 15 minutes of observations, is it OK to set my interval to 2 minutes? My phases improve dramatically when I lengthen the solution interval, which is what I expected. Just curious as to why it is suggested to use 0.1 minute solution intervals.

Thanks,
Julie
ste616
Site Admin
Posts: 220
Joined: Thu Feb 04, 2010 3:27 pm
Location: Paul Wild Observatory Narrabri NSW

Re: gpcal

Post by ste616 »

Hi Julie,

It really all depends on what the atmosphere is doing. I assume that you are talking about low frequency observations near 2 GHz. In that case, one can almost forget the atmosphere is there at all, and therefore the phase isn't likely to change much due to turbulence etc. For higher frequency observations the situation is much different. We suggest using 0.1 minute solution intervals so one can make a reasonable image even when the phase changes relatively quickly, but of course our recommendation is just a starting point to further optimisation, as you've discovered.

For your dataset, I would think that your phase is changing less than the noise on the measured phase, so increasing your solution time will indeed produce better results.
cheers
Jamie Stevens
ATCA Senior System Scientist
Post Reply