<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class=""></div><div class=""><br class=""></div>
<br class=""><div><blockquote type="cite" class=""><div class="">On 18 Sep 2017, at 5:32 PM, Eric Greisen <<a href="mailto:egreisen@nrao.edu" class="">egreisen@nrao.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">On 09/18/2017 01:57 AM, Feng Gao wrote:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">Dear Eric,<br class="">Below you can see the header information. As for UVPLT, the parameters I used are: TIMERANGE= 0 4 58 39 0 4 58 41; ANTENNA 3 0;BASELINE 8 0;BCHAN 1;ECHAN 1; DOCALIB -1; APARM 0;BPARM 6 7 1 274305.760 274305.810, 5374.7490 5374.7510 0;<br class="">The frequency difference between the 1st channel and the reference frequency is 4MHz, which I think will cause a much bigger difference. BTW, this data has been run with CVEL before, could this be the reason?<br class="">Thank you.<br class="">Feng<br class="">AIPS 1: Image=J0437+24 (UV) Filename=blu-V .av80 . 1<br class="">AIPS 1: Telescope=VLBA Receiver=VLBA<br class="">AIPS 1: Observer=BB321V0 User #= 100<br class="">AIPS 1: Observ. date=02-DEC-2013 Map date=31-AUG-2017<br class="">AIPS 1: # visibilities 195593 Sort order TB<br class="">AIPS 1: Rand axes: UU-L-SIN VV-L-SIN WW-L-SIN TIME1 SUBARRAY<br class="">AIPS 1: INTTIM GATEID CORR-ID ANTENNA1 ANTENNA2 WEIGHT<br class="">AIPS 1: SCALE<br class="">AIPS 1: ----------------------------------------------------------------<br class="">AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat<br class="">AIPS 1: COMPLEX 1 1.0000000E+00 1.00 1.0000000E+00 0.00<br class="">AIPS 1: STOKES 1 1.0000000E+00 1.00 1.0000000E+00 0.00<br class="">AIPS 1: FREQ 2 2.1900000E+10 0.50 8.0000000E+06 0.00<br class="">AIPS 1: IF 1 1.0000000E+00 1.00 1.0000000E+00 0.00<br class="">AIPS 1: RA 1 04 37 03.684 1.00 3600.000 0.00<br class="">AIPS 1: DEC 1 24 56 06.837 1.00 3600.000 0.00<br class="">AIPS 1: ----------------------------------------------------------------<br class="">AIPS 1: Coordinate equinox 2000.00<br class="">AIPS 1: Rest freq 22235.080 Vel type: OPTICAL wrt LSR<br class="">AIPS 1: Alt ref. value 4.58694E+06 wrt pixel 0.50<br class="">AIPS 1: Maximum version number of extension files of type NX is 1<br class="">AIPS 1: Maximum version number of extension files of type HI is 1<br class="">AIPS 1: Maximum version number of extension files of type FO is 1<br class="">AIPS 1: Maximum version number of extension files of type FQ is 1<br class="">AIPS 1: Maximum version number of extension files of type AN is 1<br class="">AIPS 1: Maximum version number of extension files of type WX is 1<br class="">AIPS 1: Keyword = 'OLDRFQ ' value = 2.18120000D+10<br class="">AIPS 1: Keyword = 'CORRELAT' value = 'DIFX '<br class=""></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Channel 1 is 4 MHz away from the reference pixel at 21900 MHz. This will change the uv values by about 1 part in 5000. This would be about the difference seen. NOTE that the center of the spectral channel is at 1.0 while the reference pixel is at the lower edge of the channel.</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Eric Greisen</span></div></blockquote></div><br class=""></div></body></html>